[8/9] mtd: nand: stm_nand_bch: add support for ST's BCH NAND controller

Reviewed-By: Pekon Gupta <pekon@pek-sem.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/mtd/nand/Kconfig        |    7 +
 drivers/mtd/nand/Makefile       |    1 +
 drivers/mtd/nand/stm_nand_bch.c | 1616 +++++++++++++++++++++++++++++++++++++++
 drivers/mtd/nand/stm_nand_dt.c  |  110 +++
 drivers/mtd/nand/stm_nand_dt.h  |   24 +
 include/linux/mtd/stm_nand.h    |  147 ++++
 6 files changed, 1905 insertions(+)
 create mode 100644 drivers/mtd/nand/stm_nand_bch.c
 create mode 100644 drivers/mtd/nand/stm_nand_dt.c
 create mode 100644 drivers/mtd/nand/stm_nand_dt.h
 create mode 100644 include/linux/mtd/stm_nand.h

Hi Lee,

First off, this patch has several checkpatch warnings, some of which
should be addressed:

WARNING: unnecessary whitespace before a quoted newline
#425: FILE: drivers/mtd/nand/stm_nand_bch.c:369:
+				"%s: erased page detected: \n"

WARNING: Possible unnecessary 'out of memory' message
#1362: FILE: drivers/mtd/nand/stm_nand_bch.c:1306:
+	if (!nandi->buf) {
+		dev_err(nandi->dev, "failed to allocate working buffers\n");

WARNING: Possible unnecessary 'out of memory' message
#1415: FILE: drivers/mtd/nand/stm_nand_bch.c:1359:
+	if (!nandi) {
+		dev_err(&pdev->dev,

WARNING: char * array declaration might be better as static const
#1484: FILE: drivers/mtd/nand/stm_nand_bch.c:1428:
+	const char *part_probes[] = { "cmdlinepart", "ofpart", NULL, };

WARNING: please, no space before tabs
#1948: FILE: include/linux/mtd/stm_nand.h:124:
+#define EMISS_NAND_CONFIG_HAMMING_NOT_BCH ^I(0x1 << 6)$

total: 0 errors, 7 warnings, 1915 lines checked

0008-mtd-nand-stm_nand_bch-add-support-for-ST-s-BCH-NAND-.patch has style problems, please review.

If any of these errors are false positives, please report
them to the maintainer, see CHECKPATCH in MAINTAINERS.

On Wed, Aug 27, 2014 at 01:42:23PM +0100, Lee Jones wrote:
> Reviewed-By: Pekon Gupta <pekon@pek-sem.com>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/mtd/nand/Kconfig        |    7 +
>  drivers/mtd/nand/Makefile       |    1 +
>  drivers/mtd/nand/stm_nand_bch.c | 1616 +++++++++++++++++++++++++++++++++++++++
>  drivers/mtd/nand/stm_nand_dt.c  |  110 +++
>  drivers/mtd/nand/stm_nand_dt.h  |   24 +
>  include/linux/mtd/stm_nand.h    |  147 ++++
>  6 files changed, 1905 insertions(+)
>  create mode 100644 drivers/mtd/nand/stm_nand_bch.c
>  create mode 100644 drivers/mtd/nand/stm_nand_dt.c
>  create mode 100644 drivers/mtd/nand/stm_nand_dt.h
>  create mode 100644 include/linux/mtd/stm_nand.h
> 
> diff --git a/drivers/mtd/nand/Kconfig b/drivers/mtd/nand/Kconfig
> index f1cf503..2738eec 100644
> --- a/drivers/mtd/nand/Kconfig
> +++ b/drivers/mtd/nand/Kconfig
> @@ -513,4 +513,11 @@ config MTD_NAND_XWAY
>  	  Enables support for NAND Flash chips on Lantiq XWAY SoCs. NAND is attached
>  	  to the External Bus Unit (EBU).
>  
> +config MTD_NAND_STM_BCH
> +	tristate "STMicroelectronics: NANDi BCH Controller"
> +	depends on ARCH_STI
> +	depends on OF
> +	help
> +	  Adds support for the STMicroelectronics NANDi BCH Controller.
> +
>  endif # MTD_NAND
> diff --git a/drivers/mtd/nand/Makefile b/drivers/mtd/nand/Makefile
> index a035e7c..60f374b 100644
> --- a/drivers/mtd/nand/Makefile
> +++ b/drivers/mtd/nand/Makefile
> @@ -46,6 +46,7 @@ obj-$(CONFIG_MTD_NAND_NUC900)		+= nuc900_nand.o
>  obj-$(CONFIG_MTD_NAND_MPC5121_NFC)	+= mpc5121_nfc.o
>  obj-$(CONFIG_MTD_NAND_RICOH)		+= r852.o
>  obj-$(CONFIG_MTD_NAND_JZ4740)		+= jz4740_nand.o
> +obj-$(CONFIG_MTD_NAND_STM_BCH)		+= stm_nand_bch.o stm_nand_dt.o
>  obj-$(CONFIG_MTD_NAND_GPMI_NAND)	+= gpmi-nand/
>  obj-$(CONFIG_MTD_NAND_XWAY)		+= xway_nand.o
>  obj-$(CONFIG_MTD_NAND_BCM47XXNFLASH)	+= bcm47xxnflash/
> diff --git a/drivers/mtd/nand/stm_nand_bch.c b/drivers/mtd/nand/stm_nand_bch.c
> new file mode 100644
> index 0000000..951567d
> --- /dev/null
> +++ b/drivers/mtd/nand/stm_nand_bch.c
> @@ -0,0 +1,1616 @@
> +/*
> + * Support for STMicroelectronics NANDi BCH Controller
> + *
> + * Copyright (c) 2014 STMicroelectronics Limited
> + *
> + * Authors: Angus Clark <Angus.Clark@st.com>
> + *	    Lee Jones <lee.jones@linaro.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/clk.h>
> +#include <linux/interrupt.h>
> +#include <linux/device.h>
> +#include <linux/platform_device.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/completion.h>
> +#include <linux/of_mtd.h>
> +#include <linux/mtd/nand.h>
> +#include <linux/mtd/stm_nand_bbt.h>
> +#include <linux/mtd/stm_nand.h>
> +#include <linux/mtd/partitions.h>
> +
> +#include "stm_nand_dt.h"
> +#include "stm_nand_regs.h"
> +
> +/* NANDi BCH Controller properties */
> +#define NANDI_BCH_SECTOR_SIZE			1024
> +#define NANDI_BCH_DMA_ALIGNMENT			64
> +#define NANDI_BCH_MAX_BUF_LIST			8
> +#define NANDI_BCH_BUF_LIST_SIZE			(4 * NANDI_BCH_MAX_BUF_LIST)
> +
> +/* ONFI define 6 timing modes */
> +#define ST_NAND_ONFI_TIMING_MODES		6

This is unused?

> +
> +#define PICO_TO_MILI(pico)			(pico / 1000)
> +
> +static int bch_ecc_strength[] = {
> +	[BCH_18BIT_ECC] = 18,
> +	[BCH_30BIT_ECC] = 30,
> +	[BCH_NO_ECC] = 0,
> +};
> +
> +/* BCH 'program' structure */
> +struct bch_prog {
> +	u32	multi_cs_addr[3];
> +	u32	multi_cs_config;
> +	u8	seq[16];
> +	u32	addr;
> +	u32	extra;
> +	u8	cmd[4];
> +	u32	reserved1;
> +	u32	gen_cfg;
> +	u32	delay;
> +	u32	reserved2;
> +	u32	seq_cfg;
> +};
> +
> +/* BCH template programs (modified on-the-fly) */
> +static struct bch_prog bch_prog_read_page = {
> +	.cmd = {
> +		NAND_CMD_READ0,
> +		NAND_CMD_READSTART,
> +	},
> +	.seq = {
> +		BCH_ECC_SCORE(0),
> +		BCH_CMD_ADDR,
> +		BCH_CL_CMD_1,
> +		BCH_DATA_2_SECTOR,
> +		BCH_STOP,
> +	},
> +	.gen_cfg = (GEN_CFG_DATA_8_NOT_16 |
> +		    GEN_CFG_EXTRA_ADD_CYCLE |
> +		    GEN_CFG_LAST_SEQ_NODE),
> +	.seq_cfg = SEQ_CFG_GO_STOP,
> +};
> +
> +static struct bch_prog bch_prog_write_page = {
> +	.cmd = {
> +		NAND_CMD_SEQIN,
> +		NAND_CMD_PAGEPROG,
> +		NAND_CMD_STATUS,
> +	},
> +	.seq = {
> +		BCH_CMD_ADDR,
> +		BCH_DATA_4_SECTOR,
> +		BCH_CL_CMD_1,
> +		BCH_CL_CMD_2,
> +		BCH_OP_ERR,
> +		BCH_STOP,
> +	},
> +	.gen_cfg = (GEN_CFG_DATA_8_NOT_16 |
> +		    GEN_CFG_EXTRA_ADD_CYCLE |
> +		    GEN_CFG_LAST_SEQ_NODE),
> +	.seq_cfg = (SEQ_CFG_GO_STOP |
> +		    SEQ_CFG_DATA_WRITE),
> +};
> +
> +static struct bch_prog bch_prog_erase_block = {
> +	.seq = {
> +		BCH_CL_CMD_1,
> +		BCH_AL_EX_0,
> +		BCH_AL_EX_1,
> +		BCH_AL_EX_2,
> +		BCH_CL_CMD_2,
> +		BCH_CL_CMD_3,
> +		BCH_OP_ERR,
> +		BCH_STOP,
> +	},
> +	.cmd = {
> +		NAND_CMD_ERASE1,
> +		NAND_CMD_ERASE1,
> +		NAND_CMD_ERASE2,
> +		NAND_CMD_STATUS,
> +	},
> +	.gen_cfg = (GEN_CFG_DATA_8_NOT_16 |
> +		    GEN_CFG_EXTRA_ADD_CYCLE |
> +		    GEN_CFG_LAST_SEQ_NODE),
> +	.seq_cfg = (SEQ_CFG_GO_STOP |
> +		    SEQ_CFG_ERASE),
> +};
> +
> +/* Configure BCH read/write/erase programs */
> +static void bch_configure_progs(struct nandi_controller *nandi)
> +{
> +	uint8_t data_opa = ffs(nandi->sectors_per_page) - 1;
> +	uint8_t data_instr = BCH_INSTR(BCH_OPC_DATA, data_opa);
> +	uint32_t gen_cfg_ecc = nandi->bch_ecc_mode << GEN_CFG_ECC_SHIFT;
> +
> +	/* Set 'DATA' instruction */
> +	bch_prog_read_page.seq[3] = data_instr;
> +	bch_prog_write_page.seq[1] = data_instr;
> +
> +	/* Set ECC mode */
> +	bch_prog_read_page.gen_cfg |= gen_cfg_ecc;
> +	bch_prog_write_page.gen_cfg |= gen_cfg_ecc;
> +	bch_prog_erase_block.gen_cfg |= gen_cfg_ecc;
> +
> +	/*
> +	 * Template sequences above are defined for devices that use 5 address
> +	 * cycles for page Read/Write operations (and 3 for Erase operations).
> +	 * Update sequences for devices that use 4 address cycles.
> +	 */
> +	if (!nandi->extra_addr) {
> +		/* Clear 'GEN_CFG_EXTRA_ADD_CYCLE' flag */
> +		bch_prog_read_page.gen_cfg &= ~GEN_CFG_EXTRA_ADD_CYCLE;
> +		bch_prog_write_page.gen_cfg &= ~GEN_CFG_EXTRA_ADD_CYCLE;
> +		bch_prog_erase_block.gen_cfg &= ~GEN_CFG_EXTRA_ADD_CYCLE;
> +
> +		/* Configure Erase sequence for 2 address cycles */
> +		/* (page address) */
> +		bch_prog_erase_block.seq[0] = BCH_CL_CMD_1;
> +		bch_prog_erase_block.seq[1] = BCH_AL_EX_0;
> +		bch_prog_erase_block.seq[2] = BCH_AL_EX_1;
> +		bch_prog_erase_block.seq[3] = BCH_CL_CMD_2;
> +		bch_prog_erase_block.seq[4] = BCH_CL_CMD_3;
> +		bch_prog_erase_block.seq[5] = BCH_OP_ERR;
> +		bch_prog_erase_block.seq[6] = BCH_STOP;
> +	}
> +}
> +
> +/*
> + * NANDi Interrupts (shared by Hamming and BCH controllers)
> + */
> +static irqreturn_t nandi_irq_handler(int irq, void *dev)
> +{
> +	struct nandi_controller *nandi = dev;
> +	unsigned int status;
> +
> +	status = readl(nandi->base + NANDBCH_INT_STA);
> +
> +	if (nandi->bch_ecc_mode && (status & NANDBCH_INT_SEQNODESOVER)) {
> +		/* BCH */
> +		writel(NANDBCH_INT_CLR_SEQNODESOVER,
> +		       nandi->base + NANDBCH_INT_CLR);
> +		complete(&nandi->seq_completed);
> +		return IRQ_HANDLED;
> +	}
> +	if (status & NAND_INT_RBN) {
> +		/* Hamming */
> +		writel(NAND_INT_CLR_RBN, nandi->base + NANDHAM_INT_CLR);
> +		complete(&nandi->rbn_completed);
> +		return IRQ_HANDLED;
> +	}
> +
> +	return IRQ_NONE;
> +}
> +
> +static void nandi_enable_interrupts(struct nandi_controller *nandi,
> +				    uint32_t irqs)
> +{
> +	uint32_t val;
> +
> +	val = readl(nandi->base + NANDBCH_INT_EN);
> +	val |= irqs;
> +	writel(val, nandi->base + NANDBCH_INT_EN);
> +}
> +
> +static void nandi_disable_interrupts(struct nandi_controller *nandi,
> +				     uint32_t irqs)
> +{
> +	uint32_t val;
> +
> +	val = readl(nandi->base + NANDBCH_INT_EN);
> +	val &= ~irqs;
> +	writel(val, nandi->base + NANDBCH_INT_EN);
> +}
> +
> +/*
> + * BCH Operations
> + */
> +static inline void bch_load_prog_cpu(struct nandi_controller *nandi,
> +				     struct bch_prog *prog)
> +{
> +	void __iomem *dst = nandi->base + NANDBCH_ADDRESS_REG_1;
> +	uint32_t *src = (uint32_t *)prog;
> +	int i;
> +
> +	for (i = 0; i < 16; i++) {
> +		/* Skip registers marked as "reserved" */
> +		if (i != 11 && i != 14)
> +			writel(*src, dst);
> +		src++;
> +		dst += sizeof(uint32_t *);

Are you sure you want to base the increment on the pointer size? This
looks like it might break if ever used on a 64-bit architecture. You're
probably just looking for a constant 4, or maybe sizeof(u32).

> +	}
> +}
> +
> +static void bch_wait_seq(struct nandi_controller *nandi)
> +{
> +	int ret;
> +
> +	ret = wait_for_completion_timeout(&nandi->seq_completed, HZ/2);
> +	if (!ret)
> +		dev_err(nandi->dev, "BCH Seq timeout\n");
> +}
> +
> +uint8_t bch_erase_block(struct nandi_controller *nandi,
> +			loff_t offs)
> +{
> +	struct nand_chip *chip = &nandi->info.chip;
> +	struct bch_prog *prog = &bch_prog_erase_block;
> +	uint8_t status;
> +
> +	dev_dbg(nandi->dev, "%s: offs = 0x%012llx\n", __func__, offs);
> +
> +	prog->extra = (uint32_t)(offs >> chip->page_shift);
> +
> +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> +
> +	nandi_enable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> +	reinit_completion(&nandi->seq_completed);
> +
> +	bch_load_prog_cpu(nandi, prog);
> +
> +	bch_wait_seq(nandi);
> +
> +	nandi_disable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> +
> +	status = (uint8_t)(readl(nandi->base +
> +				 NANDBCH_CHECK_STATUS_REG_A) & 0xff);
> +
> +	return status;
> +}
> +EXPORT_SYMBOL(bch_erase_block);
> +
> +static int bch_erase(struct mtd_info *mtd, int page)
> +{
> +	struct nand_chip *chip = mtd->priv;
> +	struct nandi_controller *nandi = chip->priv;
> +	uint32_t page_size = mtd->writesize;
> +	loff_t offs = (loff_t)page * page_size;
> +
> +	return bch_erase_block(nandi, offs);
> +}
> +
> +/*
> + * Detect an erased page, tolerating and correcting up to a specified number of
> + * bits at '0'.  (For many devices, it is now deemed within spec for an erased
> + * page to include a number of bits at '0', either as a result of read-disturb
> + * behaviour or 'stuck-at-zero' failures.)  Returns the number of corrected
> + * bits, or a '-1' if we have exceeded the maximum number of bits at '0' (likely
> + * to be a genuine uncorrectable ECC error).  In the latter case, the data must
> + * be returned unmodified, in accordance with the MTD API.
> + */
> +static int check_erased_page(uint8_t *data, uint32_t page_size, int max_zeros)
> +{
> +	uint8_t *b = data;
> +	int zeros = 0;
> +	int i;
> +
> +	for (i = 0; i < page_size; i++) {
> +		zeros += hweight8(~*b++);
> +		if (zeros > max_zeros)
> +			return -1;
> +	}
> +
> +	if (zeros)
> +		memset(data, 0xff, page_size);
> +
> +	return zeros;
> +}

I pointed out some flaws in this function back in July [1]. You said
you'd look into this one [2]. I really don't want to accept yet another
custom, unsound erased-page check if at all possible.

> +
> +/* Returns the number of ECC errors, or '-1' for uncorrectable error */
> +int bch_read_page(struct nandi_controller *nandi,
> +		  loff_t offs,
> +		  uint8_t *buf)
> +{
> +	struct nand_chip *chip = &nandi->info.chip;
> +	struct bch_prog *prog = &bch_prog_read_page;
> +	uint32_t page_size = nandi->info.mtd.writesize;
> +	unsigned long list_phys;

Please use dma_addr_t. This is an intentionally opaque (to some degree)
type.

> +	unsigned long buf_phys;

Ditto.

BTW, is your hardware actually restricted to a 32-bit address space? If
it has some expanded registers for larger physical address ranges, it'd
be good to handle the upper bits of the DMA address when mapping. Or
else, it would be good to reflect this in your driver with
dma_set_mask() I think.

> +	uint32_t ecc_err;
> +	int ret = 0;
> +
> +	dev_dbg(nandi->dev, "%s: offs = 0x%012llx\n", __func__, offs);
> +
> +	BUG_ON(offs & (NANDI_BCH_DMA_ALIGNMENT - 1));
> +
> +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> +
> +	nandi_enable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> +	reinit_completion(&nandi->seq_completed);
> +
> +	/* Reset ECC stats */
> +	writel(CFG_RESET_ECC_ALL | CFG_ENABLE_AFM,
> +	       nandi->base + NANDBCH_CONTROLLER_CFG);
> +	writel(CFG_ENABLE_AFM, nandi->base + NANDBCH_CONTROLLER_CFG);
> +
> +	prog->addr = (uint32_t)((offs >> (chip->page_shift - 8)) & 0xffffff00);
> +
> +	buf_phys = dma_map_single(NULL, buf, page_size, DMA_FROM_DEVICE);

Why NULL for the first arg? You should use the proper device (which will
help with the 32-bit / 64-bit masking, I think.

Also, dma_map_single() can fail. It's good practice to check the return
value with dma_mapping_error(). Same in a few other places.

> +
> +	memset(nandi->buf_list, 0x00, NANDI_BCH_BUF_LIST_SIZE);
> +	nandi->buf_list[0] = buf_phys | (nandi->sectors_per_page - 1);
> +
> +	list_phys = dma_map_single(NULL, nandi->buf_list,
> +				   NANDI_BCH_BUF_LIST_SIZE, DMA_TO_DEVICE);

Check for error.

> +
> +	writel(list_phys, nandi->base + NANDBCH_BUFFER_LIST_PTR);
> +
> +	bch_load_prog_cpu(nandi, prog);
> +
> +	bch_wait_seq(nandi);
> +
> +	nandi_disable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> +
> +	dma_unmap_single(NULL, list_phys, NANDI_BCH_BUF_LIST_SIZE,
> +			 DMA_TO_DEVICE);
> +	dma_unmap_single(NULL, buf_phys, page_size, DMA_FROM_DEVICE);
> +
> +	/* Use the maximum per-sector ECC count! */
> +	ecc_err = readl(nandi->base + NANDBCH_ECC_SCORE_REG_A) & 0xff;
> +	if (ecc_err == 0xff) {
> +		/*
> +		 * Downgrade uncorrectable ECC error for an erased page,
> +		 * tolerating 'bch_ecc_strength' bits at zero.
> +		 */
> +		ret = check_erased_page(buf, page_size, chip->ecc.strength);

I commented in [1] that you don't want to use the full ECC strength
here.

> +		if (ret >= 0)
> +			dev_dbg(nandi->dev,
> +				"%s: erased page detected: \n"
> +				"  downgrading uncorrectable ECC error.\n",
> +				__func__);
> +	} else {
> +		ret = (int)ecc_err;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(bch_read_page);
> +
> +static int bch_read(struct mtd_info *mtd, struct nand_chip *chip,
> +			 uint8_t *buf, int oob_required, int page)
> +{
> +	struct nandi_controller *nandi = chip->priv;
> +	uint32_t page_size = mtd->writesize;
> +	loff_t offs = (loff_t)page * page_size;
> +	bool bounce = false;
> +	uint8_t *p;
> +	int ret;
> +
> +	if (((unsigned int)buf & (NANDI_BCH_DMA_ALIGNMENT - 1)) ||
> +	    (!virt_addr_valid(buf))) /* vmalloc'd buffer! */

If you really need this custom DMA check, can you at least make it the
same as in bch_write_page(), and put it in a common macro / static
inline function?

> +		bounce = true;
> +
> +	p = bounce ? nandi->page_buf : buf;
> +
> +	ret = bch_read_page(nandi, offs, p);
> +	if (ret < 0)
> +		mtd->ecc_stats.failed++;
> +	else
> +		mtd->ecc_stats.corrected += ret;
> +
> +	if (bounce)
> +		memcpy(buf, p, page_size);
> +
> +	return ret;
> +}
> +
> +/* Returns the status of the NAND device following the write operation */
> +uint8_t bch_write_page(struct nandi_controller *nandi,
> +		       loff_t offs, const uint8_t *buf)
> +{
> +	struct nand_chip *chip = &nandi->info.chip;
> +	struct bch_prog *prog = &bch_prog_write_page;
> +	uint32_t page_size = nandi->info.mtd.writesize;
> +	uint8_t *p = (uint8_t *)buf;
> +	unsigned long list_phys;
> +	unsigned long buf_phys;
> +	uint8_t status;
> +	bool bounce = false;
> +
> +	dev_dbg(nandi->dev, "%s: offs = 0x%012llx\n", __func__, offs);
> +
> +	BUG_ON(offs & (page_size - 1));
> +
> +	if (((unsigned long)buf & (NANDI_BCH_DMA_ALIGNMENT - 1)) ||
> +	    !virt_addr_valid(buf)) { /* vmalloc'd buffer! */
> +		bounce = true;
> +	}
> +
> +	if (bounce) {
> +		memcpy(nandi->page_buf, buf, page_size);
> +		p = nandi->page_buf;
> +		nandi->cached_page = -1;
> +	}
> +
> +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> +
> +	nandi_enable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> +	reinit_completion(&nandi->seq_completed);
> +
> +	prog->addr = (uint32_t)((offs >> (chip->page_shift - 8)) & 0xffffff00);
> +
> +	buf_phys = dma_map_single(NULL, p, page_size, DMA_TO_DEVICE);

Check for error.

> +	memset(nandi->buf_list, 0x00, NANDI_BCH_BUF_LIST_SIZE);
> +	nandi->buf_list[0] = buf_phys | (nandi->sectors_per_page - 1);
> +
> +	list_phys = dma_map_single(NULL, nandi->buf_list,
> +				   NANDI_BCH_BUF_LIST_SIZE, DMA_TO_DEVICE);

Check for error.

> +
> +	writel(list_phys, nandi->base + NANDBCH_BUFFER_LIST_PTR);
> +
> +	bch_load_prog_cpu(nandi, prog);
> +
> +	bch_wait_seq(nandi);
> +
> +	nandi_disable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> +
> +	dma_unmap_single(NULL, list_phys, NANDI_BCH_BUF_LIST_SIZE,
> +			 DMA_TO_DEVICE);
> +	dma_unmap_single(NULL, buf_phys, page_size, DMA_FROM_DEVICE);
> +
> +	status = (uint8_t)(readl(nandi->base +
> +				 NANDBCH_CHECK_STATUS_REG_A) & 0xff);
> +
> +	return status;
> +}
> +EXPORT_SYMBOL(bch_write_page);
> +
> +static int bch_write(struct mtd_info *mtd, struct nand_chip *chip,
> +		     uint32_t offset, int data_len, const uint8_t *buf,
> +		     int oob_required, int page, int cached, int raw)
> +{
> +	struct nandi_controller *nandi = chip->priv;
> +	uint32_t page_size = mtd->writesize;
> +	loff_t offs = (loff_t)page * page_size;
> +	int ret;
> +
> +	ret = bch_write_page(nandi, offs, buf);
> +	if (ret & NAND_STATUS_FAIL)
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +/*
> + * Hamming-FLEX operations
> + */
> +static int flex_wait_rbn(struct nandi_controller *nandi)
> +{
> +	int ret;
> +
> +	ret = wait_for_completion_timeout(&nandi->rbn_completed, HZ/2);
> +	if (!ret)
> +		dev_err(nandi->dev, "FLEX RBn timeout\n");
> +
> +	return ret;
> +}
> +
> +static void flex_cmd(struct nandi_controller *nandi, uint8_t cmd)
> +{
> +	uint32_t val;
> +
> +	val = (FLEX_CMD_CSN | FLEX_CMD_BEATS_1 | cmd);
> +	writel(val, nandi->base + NANDHAM_FLEX_CMD);
> +}
> +
> +static void flex_addr(struct nandi_controller *nandi,
> +		      uint32_t addr, int cycles)
> +{
> +	addr &= 0x00ffffff;
> +
> +	BUG_ON(cycles < 1);
> +	BUG_ON(cycles > 3);
> +
> +	addr |= (FLEX_ADDR_CSN | FLEX_ADDR_ADD8_VALID);
> +	addr |= (cycles & 0x3) << 28;
> +
> +	writel(addr, nandi->base + NANDHAM_FLEX_ADD);
> +}
> +
> +/*
> + * Partial implementation of MTD/NAND Interface, based on Hamming-FLEX
> + * operation.
> + *
> + * Allows us to make use of nand_base.c functions where possible
> + * (e.g. nand_scan_ident() and friends).
> + */
> +static void flex_command_lp(struct mtd_info *mtd, unsigned int command,
> +			    int column, int page)
> +{
> +	struct nand_chip *chip = mtd->priv;
> +	struct nandi_controller *nandi = chip->priv;
> +
> +	emiss_nandi_select(nandi, STM_NANDI_HAMMING);
> +
> +	switch (command) {
> +	case NAND_CMD_READOOB:
> +		/* Emulate NAND_CMD_READOOB */
> +		column += mtd->writesize;
> +		command = NAND_CMD_READ0;
> +		break;
> +	case NAND_CMD_READ0:
> +	case NAND_CMD_ERASE1:
> +	case NAND_CMD_SEQIN:
> +	case NAND_CMD_RESET:
> +	case NAND_CMD_PARAM:
> +		/* Prime RBn wait */
> +		nandi_enable_interrupts(nandi, NAND_INT_RBN);
> +		reinit_completion(&nandi->rbn_completed);
> +		break;
> +	case NAND_CMD_READID:
> +	case NAND_CMD_STATUS:
> +	case NAND_CMD_ERASE2:
> +		break;
> +	default:
> +		/* Catch unexpected commands */
> +		BUG();
> +	}
> +
> +	/*
> +	 * Command Cycle
> +	 */
> +	flex_cmd(nandi, command);
> +
> +	/*
> +	 * Address Cycles
> +	 */
> +	if (column != -1)
> +		flex_addr(nandi, column,
> +			  (command == NAND_CMD_READID) ? 1 : 2);
> +
> +	if (page != -1)
> +		flex_addr(nandi, page, nandi->extra_addr ? 3 : 2);
> +
> +	/* Complete 'READ0' command */
> +	if (command == NAND_CMD_READ0)
> +		flex_cmd(nandi, NAND_CMD_READSTART);
> +
> +	/* Wait for RBn, if required                        */
> +	/* (Note, other commands may handle wait elsewhere) */
> +	if (command == NAND_CMD_RESET ||
> +	    command == NAND_CMD_READ0 ||
> +	    command == NAND_CMD_PARAM) {
> +		flex_wait_rbn(nandi);
> +		nandi_disable_interrupts(nandi, NAND_INT_RBN);
> +	}
> +}
> +
> +static uint8_t flex_read_byte(struct mtd_info *mtd)
> +{
> +	struct nand_chip *chip = mtd->priv;
> +	struct nandi_controller *nandi = chip->priv;
> +
> +	emiss_nandi_select(nandi, STM_NANDI_HAMMING);
> +
> +	return (uint8_t)(readl(nandi->base + NANDHAM_FLEX_DATA) & 0xff);
> +}
> +
> +static int flex_wait_func(struct mtd_info *mtd, struct nand_chip *chip)
> +{
> +	struct nandi_controller *nandi = chip->priv;
> +
> +	emiss_nandi_select(nandi, STM_NANDI_HAMMING);
> +
> +	flex_wait_rbn(nandi);
> +
> +	flex_cmd(nandi, NAND_CMD_STATUS);
> +
> +	return (int)(readl(nandi->base + NANDHAM_FLEX_DATA) & 0xff);
> +}
> +
> +/* Multi-CS devices not supported */
> +static void flex_select_chip(struct mtd_info *mtd, int chipnr)
> +{
> +
> +}
> +
> +static void flex_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
> +{
> +	struct nand_chip *chip = mtd->priv;
> +	struct nandi_controller *nandi = chip->priv;
> +	int aligned;
> +
> +	emiss_nandi_select(nandi, STM_NANDI_HAMMING);
> +
> +	/* Read bytes until buf is 4-byte aligned */
> +	while (len && ((unsigned int)buf & 0x3)) {
> +		*buf++ = (uint8_t)(readl(nandi->base + NANDHAM_FLEX_DATA)
> +				   & 0xff);
> +		len--;
> +	};
> +
> +	/* Use 'BEATS_4'/readsl */
> +	if (len > 8) {
> +		aligned = len & ~0x3;
> +		writel(FLEX_DATA_CFG_BEATS_4 | FLEX_DATA_CFG_CSN,
> +		       nandi->base + NANDHAM_FLEX_DATAREAD_CONFIG);
> +
> +		readsl(nandi->base + NANDHAM_FLEX_DATA, buf, aligned >> 2);
> +
> +		buf += aligned;
> +		len -= aligned;
> +
> +		writel(FLEX_DATA_CFG_BEATS_1 | FLEX_DATA_CFG_CSN,
> +		       nandi->base + NANDHAM_FLEX_DATAREAD_CONFIG);
> +	}
> +
> +	/* Mop up remaining bytes */
> +	while (len > 0) {
> +		*buf++ = (uint8_t)(readl(nandi->base + NANDHAM_FLEX_DATA)
> +				   & 0xff);
> +		len--;
> +	}
> +}
> +
> +static void flex_write_buf(struct mtd_info *mtd, const uint8_t *buf, int len)
> +{
> +	struct nand_chip *chip = mtd->priv;
> +	struct nandi_controller *nandi = chip->priv;
> +	int aligned;
> +
> +	/* Write bytes until buf is 4-byte aligned */
> +	while (len && ((unsigned int)buf & 0x3)) {
> +		writel(*buf++, nandi->base + NANDHAM_FLEX_DATA);
> +		len--;
> +	};
> +
> +	/* USE 'BEATS_4/writesl */
> +	if (len > 8) {
> +		aligned = len & ~0x3;
> +		writel(FLEX_DATA_CFG_BEATS_4 | FLEX_DATA_CFG_CSN,
> +		       nandi->base + NANDHAM_FLEX_DATAWRITE_CONFIG);
> +		writesl(nandi->base + NANDHAM_FLEX_DATA, buf, aligned >> 2);
> +		buf += aligned;
> +		len -= aligned;
> +		writel(FLEX_DATA_CFG_BEATS_1 | FLEX_DATA_CFG_CSN,
> +		       nandi->base + NANDHAM_FLEX_DATAWRITE_CONFIG);
> +	}
> +
> +	/* Mop up remaining bytes */
> +	while (len > 0) {
> +		writel(*buf++, nandi->base + NANDHAM_FLEX_DATA);
> +		len--;
> +	}
> +}
> +
> +int flex_read_raw(struct nandi_controller *nandi,
> +			 uint32_t page_addr,
> +			 uint32_t col_addr,
> +			 uint8_t *buf, uint32_t len)
> +{
> +	dev_dbg(nandi->dev, "%s %u bytes at [0x%06x,0x%04x]\n",
> +		__func__, len, page_addr, col_addr);
> +
> +	BUG_ON(len & 0x3);
> +	BUG_ON((unsigned long)buf & 0x3);
> +
> +	emiss_nandi_select(nandi, STM_NANDI_HAMMING);
> +	nandi_enable_interrupts(nandi, NAND_INT_RBN);
> +	reinit_completion(&nandi->rbn_completed);
> +
> +	writel(FLEX_DATA_CFG_BEATS_4 | FLEX_DATA_CFG_CSN,
> +	       nandi->base + NANDHAM_FLEX_DATAREAD_CONFIG);
> +
> +	flex_cmd(nandi, NAND_CMD_READ0);
> +	flex_addr(nandi, col_addr, 2);
> +	flex_addr(nandi, page_addr, nandi->extra_addr ? 3 : 2);
> +	flex_cmd(nandi, NAND_CMD_READSTART);
> +
> +	flex_wait_rbn(nandi);
> +
> +	readsl(nandi->base + NANDHAM_FLEX_DATA, buf, len / 4);
> +
> +	nandi_disable_interrupts(nandi, NAND_INT_RBN);
> +
> +	writel(FLEX_DATA_CFG_BEATS_1 | FLEX_DATA_CFG_CSN,
> +	       nandi->base + NANDHAM_FLEX_DATAREAD_CONFIG);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(flex_read_raw);
> +
> +static int bch_mtd_read_oob(struct mtd_info *mtd,
> +			    struct nand_chip *chip, int page)
> +{
> +	BUG();

Are you sure this can't be implemented, even if it's not the expected
mode of operation? That's really unforunate.

> +	return 0;
> +}
> +
> +static int bch_mtd_write_oob(struct mtd_info *mtd,
> +			     struct nand_chip *chip, int page)
> +{
> +	BUG();

Same question.

> +	return 0;
> +}
> +
> +static int bch_read_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
> +			     uint8_t *buf, int oob_required, int page)
> +{
> +	BUG();

Same question.

> +	return 0;
> +}
> +
> +static int bch_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
> +			      const uint8_t *buf, int oob_required)
> +{
> +	BUG();

Same question.

> +	return 0;
> +}
> +
> +static void bch_hwctl(struct mtd_info *mtd, int mode)
> +{
> +	BUG();
> +}
> +
> +static int bch_calculate(struct mtd_info *mtd, const uint8_t *dat,
> +			 uint8_t *ecc_code)
> +{
> +	BUG();
> +	return 0;
> +}
> +
> +static int bch_correct(struct mtd_info *mtd, uint8_t *dat, uint8_t *read_ecc,
> +		       uint8_t *calc_ecc)
> +{
> +	BUG();
> +	return 0;
> +}
> +
> +/*
> + * Initialisation
> + */
> +static int bch_check_compatibility(struct nandi_controller *nandi,
> +				   struct mtd_info *mtd,
> +				   struct nand_chip *chip)
> +{
> +	if (chip->bits_per_cell > 1)
> +		dev_warn(nandi->dev, "MLC NAND not fully supported\n");
> +
> +	if (chip->options & NAND_BUSWIDTH_16) {
> +		dev_err(nandi->dev, "x16 NAND not supported\n");
> +		return false;
> +	}
> +
> +	if (nandi->blocks_per_device / 4 > mtd->writesize) {
> +		/* Need to implement multi-page BBT support... */
> +		dev_err(nandi->dev, "BBT too big to fit in single page\n");
> +		return false;
> +	}
> +
> +	if (bch_ecc_sizes[nandi->bch_ecc_mode] * nandi->sectors_per_page >
> +	    mtd->oobsize) {
> +		dev_err(nandi->dev, "insufficient OOB for selected ECC\n");
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +/* Select strongest ECC scheme compatible with OOB size */
> +static int bch_set_ecc_auto(struct nandi_controller *nandi,
> +			    struct mtd_info *mtd)
> +{
> +	int oob_bytes_per_sector = mtd->oobsize / nandi->sectors_per_page;
> +	int try_ecc_modes[] = { BCH_30BIT_ECC, BCH_18BIT_ECC, -1 };
> +	int m, ecc_mode;
> +
> +	for (m = 0; try_ecc_modes[m] >= 0; m++) {
> +		ecc_mode = try_ecc_modes[m];
> +		if (oob_bytes_per_sector >= bch_ecc_sizes[ecc_mode]) {
> +			nandi->bch_ecc_mode = ecc_mode;
> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static void nandi_set_mtd_defaults(struct nandi_controller *nandi,
> +				   struct mtd_info *mtd, struct nand_chip *chip)
> +{
> +	struct nandi_info *info = &nandi->info;
> +	int i;
> +
> +	/* ecclayout */
> +	info->ecclayout.eccbytes = mtd->oobsize;
> +	for (i = 0; i < 64; i++)
> +		info->ecclayout.eccpos[i] = i;
> +	info->ecclayout.oobfree[0].offset = 0;
> +	info->ecclayout.oobfree[0].length = 0;
> +	chip->ecc.mode = NAND_ECC_HW;
> +
> +	/* nand_chip */
> +	chip->controller = &chip->hwcontrol;
> +	spin_lock_init(&chip->controller->lock);
> +	init_waitqueue_head(&chip->controller->wq);
> +	chip->state = FL_READY;
> +	chip->priv = nandi;
> +	chip->ecc.layout = &info->ecclayout;
> +	chip->options |= NAND_NO_SUBPAGE_WRITE;
> +
> +	chip->cmdfunc = flex_command_lp;
> +	chip->read_byte = flex_read_byte;
> +	chip->select_chip = flex_select_chip;
> +	chip->waitfunc = flex_wait_func;
> +	chip->read_buf = flex_read_buf;
> +	chip->write_buf = flex_write_buf;
> +
> +	chip->bbt_options |= NAND_BBT_USE_FLASH;
> +
> +	/* mtd_info */
> +	mtd->owner = THIS_MODULE;
> +	mtd->type = MTD_NANDFLASH;
> +	mtd->flags = MTD_CAP_NANDFLASH;
> +	mtd->ecclayout = &info->ecclayout;
> +
> +	chip->ecc.hwctl = bch_hwctl;
> +	chip->ecc.calculate = bch_calculate;
> +	chip->ecc.correct = bch_correct;
> +
> +	chip->ecc.read_oob = bch_mtd_read_oob;
> +	chip->ecc.write_oob = bch_mtd_write_oob;
> +
> +	chip->ecc.read_page = bch_read;
> +	chip->ecc.read_page_raw = bch_read_page_raw;
> +	chip->ecc.write_page_raw = bch_write_page_raw;
> +	chip->write_page = bch_write;
> +	chip->erase = bch_erase;
> +
> +#ifdef CONFIG_MTD_NAND_STM_BCH_BBT

This #ifdef won't work right when you build the BBT code as a module.
You may need IS_ENABLED(), and you'll have to ensure you can't make this
driver built-in while the BBT code is a module.

One option: just disallow building your BBT code as a module.

> +	chip->scan_bbt = bch_scan_bbt;
> +	chip->block_bad = bch_block_isbad;
> +	chip->block_markbad = bch_block_markbad;
> +#endif
> +}
> +
> +/*
> + * Timing and Clocks
> + */
> +
> +static void nandi_clk_enable(struct nandi_controller *nandi)
> +{
> +	clk_prepare_enable(nandi->emi_clk);
> +	clk_prepare_enable(nandi->bch_clk);
> +}
> +
> +static void nandi_clk_disable(struct nandi_controller *nandi)
> +{
> +	clk_disable_unprepare(nandi->emi_clk);
> +	clk_disable_unprepare(nandi->bch_clk);
> +}
> +
> +static struct clk *nandi_clk_setup(struct nandi_controller *nandi,
> +				   char *clkname)
> +{
> +	struct clk *clk;
> +	int ret;
> +
> +	clk = devm_clk_get(nandi->dev, clkname);
> +	if (IS_ERR_OR_NULL(clk)) {
> +		dev_warn(nandi->dev, "Failed to get %s clock\n", clkname);
> +		return NULL;
> +	}
> +
> +	ret = clk_prepare_enable(clk);
> +	if (ret) {
> +		dev_warn(nandi->dev, "Failed to enable %s clock\n", clkname);
> +		return NULL;
> +	}
> +
> +	return clk;
> +}
> +
> +/* Derive Hamming-FLEX timing register values from 'nand_sdr_timings' data */
> +static void flex_calc_timing_registers(const struct nand_sdr_timings *spec,
> +				       int tCLK, int relax,
> +				       uint32_t *ctl_timing,
> +				       uint32_t *wen_timing,
> +				       uint32_t *ren_timing)
> +{
> +	int tMAX_HOLD;
> +	int n_ctl_setup;
> +	int n_ctl_hold;
> +	int n_ctl_wb;
> +
> +	int tMAX_WEN_OFF;
> +	int n_wen_on;
> +	int n_wen_off;
> +
> +	int tMAX_REN_OFF;
> +	int n_ren_on;
> +	int n_ren_off;
> +
> +	/*
> +	 * CTL_TIMING
> +	 */
> +
> +	/*	- SETUP */
> +	n_ctl_setup = (PICO_TO_MILI(spec->tCLS_min - spec->tWP_min)
> +		       + tCLK - 1) / tCLK;
> +	if (n_ctl_setup < 1)
> +		n_ctl_setup = 1;
> +	n_ctl_setup += relax;
> +
> +	/*	- HOLD */
> +	tMAX_HOLD = spec->tCLH_min;
> +	if (spec->tCH_min > tMAX_HOLD)
> +		tMAX_HOLD = spec->tCH_min;
> +	if (spec->tALH_min > tMAX_HOLD)
> +		tMAX_HOLD = spec->tALH_min;
> +	if (spec->tDH_min > tMAX_HOLD)
> +		tMAX_HOLD = spec->tDH_min;
> +	n_ctl_hold = (PICO_TO_MILI(tMAX_HOLD) + tCLK - 1) / tCLK + relax;
> +
> +	/*	- CE_deassert_hold = 0 */
> +
> +	/*	- WE_high_to_RBn_low */
> +	n_ctl_wb = (PICO_TO_MILI(spec->tWB_max) + tCLK - 1) / tCLK;
> +
> +	*ctl_timing = ((n_ctl_setup & 0xff) |
> +		       (n_ctl_hold & 0xff) << 8 |
> +		       (n_ctl_wb & 0xff) << 24);
> +
> +	/*
> +	 * WEN_TIMING
> +	 */
> +
> +	/*	- ON */
> +	n_wen_on = (PICO_TO_MILI(spec->tWH_min) + tCLK - 1) / tCLK + relax;
> +
> +	/*	- OFF */
> +	tMAX_WEN_OFF = spec->tWC_min - spec->tWH_min;
> +	if (spec->tWP_min > tMAX_WEN_OFF)
> +		tMAX_WEN_OFF = spec->tWP_min;
> +	n_wen_off = (PICO_TO_MILI(tMAX_WEN_OFF) + tCLK - 1) / tCLK + relax;
> +
> +	*wen_timing = ((n_wen_on & 0xff) |
> +		       (n_wen_off & 0xff) << 8);
> +
> +	/*
> +	 * REN_TIMING
> +	 */
> +
> +	/*	- ON */
> +	n_ren_on = (PICO_TO_MILI(spec->tREH_min) + tCLK - 1) / tCLK + relax;
> +
> +	/*	- OFF */
> +	tMAX_REN_OFF = spec->tRC_min - spec->tREH_min;
> +	if (spec->tRP_min > tMAX_REN_OFF)
> +		tMAX_REN_OFF = spec->tRP_min;
> +	if (spec->tREA_max > tMAX_REN_OFF)
> +		tMAX_REN_OFF = spec->tREA_max;
> +	n_ren_off = (PICO_TO_MILI(tMAX_REN_OFF) + tCLK - 1) / tCLK + 1 + relax;
> +
> +	*ren_timing = ((n_ren_on & 0xff) |
> +		       (n_ren_off & 0xff) << 8);
> +}
> +
> +/* Derive BCH timing register values from 'nand_sdr_timings' data */
> +static void bch_calc_timing_registers(const struct nand_sdr_timings *spec,
> +				      int tCLK, int relax,
> +				      uint32_t *ctl_timing,
> +				      uint32_t *wen_timing,
> +				      uint32_t *ren_timing)
> +{
> +	int tMAX_HOLD;
> +	int n_ctl_setup;
> +	int n_ctl_hold;
> +	int n_ctl_wb;
> +
> +	int n_wen_on;
> +	int n_wen_off;
> +	int wen_half_on;
> +	int wen_half_off;
> +
> +	int tMAX_REN_ON;
> +	int tMAX_CS_DEASSERT;
> +	int n_d_latch;
> +	int n_telqv;
> +	int n_ren_on;
> +	int n_ren_off;
> +
> +	/*
> +	 * CTL_TIMING
> +	 */
> +
> +	/*	- SETUP */
> +	if (spec->tCLS_min > spec->tWP_min)
> +		n_ctl_setup = (PICO_TO_MILI(spec->tCLS_min - spec->tWP_min)
> +			       + tCLK - 1) / tCLK;
> +	else
> +		n_ctl_setup = 0;
> +	n_ctl_setup += relax;
> +
> +	/*	- HOLD */
> +	tMAX_HOLD = spec->tCLH_min;
> +	if (spec->tCH_min > tMAX_HOLD)
> +		tMAX_HOLD = spec->tCH_min;
> +	if (spec->tALH_min > tMAX_HOLD)
> +		tMAX_HOLD = spec->tALH_min;
> +	if (spec->tDH_min > tMAX_HOLD)
> +		tMAX_HOLD = spec->tDH_min;
> +	n_ctl_hold = (PICO_TO_MILI(tMAX_HOLD) + tCLK - 1) / tCLK + relax;
> +	/*	- CE_deassert_hold = 0 */
> +
> +	/*	- WE_high_to_RBn_low */
> +	n_ctl_wb = (PICO_TO_MILI(spec->tWB_max) + tCLK - 1) / tCLK;
> +
> +	*ctl_timing = ((n_ctl_setup & 0xff) |
> +		       (n_ctl_hold & 0xff) << 8 |
> +		       (n_ctl_wb & 0xff) << 24);
> +
> +	/*
> +	 * WEN_TIMING
> +	 */
> +
> +	/*	- ON */
> +	n_wen_on = (2 * PICO_TO_MILI(spec->tWH_min) + tCLK - 1) / tCLK;
> +	wen_half_on = n_wen_on % 2;
> +	n_wen_on /= 2;
> +	n_wen_on += relax;
> +
> +	/*	- OFF */
> +	n_wen_off = (2 * PICO_TO_MILI(spec->tWP_min) + tCLK - 1) / tCLK;
> +	wen_half_off = n_wen_off % 2;
> +	n_wen_off /= 2;
> +	n_wen_off += relax;
> +
> +	*wen_timing = ((n_wen_on & 0xff) |
> +		       (n_wen_off & 0xff) << 8 |
> +		       (wen_half_on << 16) |
> +		       (wen_half_off << 17));
> +
> +	/*
> +	 * REN_TIMING
> +	 */
> +
> +	/*	- ON */
> +	tMAX_REN_ON = spec->tRC_min - spec->tRP_min;
> +	if (spec->tREH_min > tMAX_REN_ON)
> +		tMAX_REN_ON = spec->tREH_min;
> +
> +	n_ren_on = (2 * PICO_TO_MILI(tMAX_REN_ON) + tCLK - 1) / tCLK;
> +	n_ren_on /= 2;
> +	n_ren_on += relax;
> +
> +	/*	- OFF */
> +	n_ren_off = (2 * PICO_TO_MILI(spec->tREA_max) + tCLK - 1) / tCLK;
> +	n_ren_off /= 2;
> +	n_ren_off += relax;
> +
> +	/*	- DATA_LATCH */
> +	if (PICO_TO_MILI(spec->tREA_max) <=
> +	    (PICO_TO_MILI(spec->tRP_min) - (2 * tCLK)))
> +		n_d_latch = 0;
> +	else if (PICO_TO_MILI(spec->tREA_max) <=
> +		 (PICO_TO_MILI(spec->tRP_min) - tCLK))
> +		n_d_latch = 1;
> +	else if ((spec->tREA_max <= spec->tRP_min) &&
> +		 (PICO_TO_MILI(spec->tRHOH_min) >= 2 * tCLK))
> +		n_d_latch = 2;
> +	else
> +		n_d_latch = 3;
> +
> +	/*	- TELQV */
> +	tMAX_CS_DEASSERT = spec->tCOH_min;
> +	if (spec->tCHZ_max > tMAX_CS_DEASSERT)
> +		tMAX_CS_DEASSERT = spec->tCHZ_max;
> +
> +	n_telqv = (PICO_TO_MILI(tMAX_CS_DEASSERT) + tCLK - 1) / tCLK;
> +
> +	*ren_timing = ((n_ren_on & 0xff) |
> +		       (n_ren_off & 0xff) << 8 |
> +		       (n_d_latch & 0x3) << 16 |
> +		       (wen_half_on << 18) |
> +		       (wen_half_off << 19) |
> +		       (n_telqv & 0xff) << 24);
> +}
> +
> +static void flex_configure_timing_registers(struct nandi_controller *nandi,
> +					    const struct nand_sdr_timings *spec,
> +					    int relax)
> +{
> +	uint32_t ctl_timing;
> +	uint32_t wen_timing;
> +	uint32_t ren_timing;
> +	int emi_t_ns;
> +
> +	/* Select Hamming Controller */
> +	emiss_nandi_select(nandi, STM_NANDI_HAMMING);
> +
> +	/* Get EMI clock (default 100MHz) */
> +	if (nandi->emi_clk)
> +		emi_t_ns = 1000000000UL / clk_get_rate(nandi->emi_clk);
> +	else {
> +		dev_warn(nandi->dev,
> +			 "No EMI clock available; assuming default 100MHz\n");
> +		emi_t_ns = 10;
> +	}
> +
> +	/* Derive timing register values from specification */
> +	flex_calc_timing_registers(spec, emi_t_ns, relax,
> +				   &ctl_timing, &wen_timing, &ren_timing);
> +
> +	dev_dbg(nandi->dev,
> +		"updating FLEX timing configuration [0x%08x, 0x%08x, 0x%08x]\n",
> +		ctl_timing, wen_timing, ren_timing);
> +
> +	/* Program timing registers */
> +	writel(ctl_timing, nandi->base + NANDHAM_CTL_TIMING);
> +	writel(wen_timing, nandi->base + NANDHAM_WEN_TIMING);
> +	writel(ren_timing, nandi->base + NANDHAM_REN_TIMING);
> +}
> +
> +static void bch_configure_timing_registers(struct nandi_controller *nandi,
> +					   const struct nand_sdr_timings *spec,
> +					   int relax)
> +{
> +	uint32_t ctl_timing;
> +	uint32_t wen_timing;
> +	uint32_t ren_timing;
> +	int bch_t_ns;
> +
> +	/* Select BCH Controller */
> +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> +
> +	/* Get BCH clock (default 200MHz) */
> +	if (nandi->bch_clk)
> +		bch_t_ns = 1000000000UL / clk_get_rate(nandi->bch_clk);
> +	else {
> +		dev_warn(nandi->dev,
> +			 "No BCH clock available; assuming default 200MHz\n");
> +		bch_t_ns = 5;
> +	}
> +
> +	/* Derive timing register values from specification */
> +	bch_calc_timing_registers(spec, bch_t_ns, relax,
> +				  &ctl_timing, &wen_timing, &ren_timing);
> +
> +	dev_dbg(nandi->dev,
> +		"updating BCH timing configuration [0x%08x, 0x%08x, 0x%08x]\n",
> +		ctl_timing, wen_timing, ren_timing);
> +
> +	/* Program timing registers */
> +	writel(ctl_timing, nandi->base + NANDBCH_CTL_TIMING);
> +	writel(wen_timing, nandi->base + NANDBCH_WEN_TIMING);
> +	writel(ren_timing, nandi->base + NANDBCH_REN_TIMING);
> +}
> +
> +static void nandi_configure_timing_registers(struct nandi_controller *nandi,
> +					const struct nand_sdr_timings *spec,
> +					int relax)
> +{
> +	bch_configure_timing_registers(nandi, spec, relax);
> +	flex_configure_timing_registers(nandi, spec, relax);
> +}
> +
> +static void nandi_init_hamming(struct nandi_controller *nandi, int emi_bank)
> +{
> +	dev_dbg(nandi->dev, "%s\n", __func__);
> +
> +	emiss_nandi_select(nandi, STM_NANDI_HAMMING);
> +
> +	/* Reset and disable boot-mode controller */
> +	writel(BOOT_CFG_RESET, nandi->base + NANDHAM_BOOTBANK_CFG);
> +	udelay(1);
> +	writel(0x00000000, nandi->base + NANDHAM_BOOTBANK_CFG);
> +
> +	/* Reset controller */
> +	writel(CFG_RESET, nandi->base + NANDHAM_FLEXMODE_CFG);
> +	udelay(1);
> +	writel(0x00000000, nandi->base + NANDHAM_FLEXMODE_CFG);
> +
> +	/* Set EMI Bank */
> +	writel(0x1 << emi_bank, nandi->base + NANDHAM_FLEX_MUXCTRL);
> +
> +	/* Enable FLEX mode */
> +	writel(CFG_ENABLE_FLEX, nandi->base + NANDHAM_FLEXMODE_CFG);
> +
> +	/* Configure FLEX_DATA_READ/WRITE for 1-byte access */
> +	writel(FLEX_DATA_CFG_BEATS_1 | FLEX_DATA_CFG_CSN,
> +	       nandi->base + NANDHAM_FLEX_DATAREAD_CONFIG);
> +	writel(FLEX_DATA_CFG_BEATS_1 | FLEX_DATA_CFG_CSN,
> +	       nandi->base + NANDHAM_FLEX_DATAREAD_CONFIG);
> +
> +	/* RBn interrupt on rising edge */
> +	writel(NAND_EDGE_CFG_RBN_RISING, nandi->base + NANDHAM_INT_EDGE_CFG);
> +
> +	/* Enable interrupts */
> +	nandi_enable_interrupts(nandi, NAND_INT_ENABLE);
> +}
> +
> +static void nandi_init_bch(struct nandi_controller *nandi, int emi_bank)
> +{
> +	dev_dbg(nandi->dev, "%s\n", __func__);
> +
> +	/* Initialise BCH Controller */
> +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> +
> +	/* Reset and disable boot-mode controller */
> +	writel(BOOT_CFG_RESET, nandi->base + NANDBCH_BOOTBANK_CFG);
> +	udelay(1);
> +	writel(0x00000000, nandi->base + NANDBCH_BOOTBANK_CFG);
> +
> +	/* Reset AFM controller */
> +	writel(CFG_RESET, nandi->base + NANDBCH_CONTROLLER_CFG);
> +	udelay(1);
> +	writel(0x00000000, nandi->base + NANDBCH_CONTROLLER_CFG);
> +
> +	/* Set EMI Bank */
> +	writel(0x1 << emi_bank, nandi->base + NANDBCH_FLEX_MUXCTRL);
> +
> +	/* Reset ECC stats */
> +	writel(CFG_RESET_ECC_ALL, nandi->base + NANDBCH_CONTROLLER_CFG);
> +	udelay(1);
> +
> +	/* Enable AFM */
> +	writel(CFG_ENABLE_AFM, nandi->base + NANDBCH_CONTROLLER_CFG);
> +
> +	/* Configure Read DMA Plugs (values supplied by Validation) */
> +	writel(0x00000005, nandi->dma + EMISS_NAND_RD_DMA_PAGE_SIZE);
> +	writel(0x00000005, nandi->dma + EMISS_NAND_RD_DMA_MAX_OPCODE_SIZE);
> +	writel(0x00000002, nandi->dma + EMISS_NAND_RD_DMA_MIN_OPCODE_SIZE);
> +	writel(0x00000001, nandi->dma + EMISS_NAND_RD_DMA_MAX_CHUNK_SIZE);
> +	writel(0x00000000, nandi->dma + EMISS_NAND_RD_DMA_MAX_MESSAGE_SIZE);
> +
> +	/* Configure Write DMA Plugs (values supplied by Validation) */
> +	writel(0x00000005, nandi->dma + EMISS_NAND_WR_DMA_PAGE_SIZE);
> +	writel(0x00000005, nandi->dma + EMISS_NAND_WR_DMA_MAX_OPCODE_SIZE);
> +	writel(0x00000002, nandi->dma + EMISS_NAND_WR_DMA_MIN_OPCODE_SIZE);
> +	writel(0x00000001, nandi->dma + EMISS_NAND_WR_DMA_MAX_CHUNK_SIZE);
> +	writel(0x00000000, nandi->dma + EMISS_NAND_WR_DMA_MAX_MESSAGE_SIZE);
> +
> +	nandi_enable_interrupts(nandi, NAND_INT_ENABLE);
> +}
> +
> +static void nandi_init_controller(struct nandi_controller *nandi,
> +				  int emi_bank)
> +{
> +	nandi_init_bch(nandi, emi_bank);
> +	nandi_init_hamming(nandi, emi_bank);
> +}
> +
> +/* Initialise working buffers, accomodating DMA alignment constraints */
> +static int nandi_init_working_buffers(struct nandi_controller *nandi,
> +				      struct nandi_bbt_info *bbt_info,
> +				      struct mtd_info *mtd)
> +{
> +	uint32_t bbt_buf_size;
> +	uint32_t buf_size;
> +
> +	/*	- Page and OOB */
> +	buf_size = mtd->writesize + mtd->oobsize + NANDI_BCH_DMA_ALIGNMENT;
> +
> +	/*	- BBT data (page-size aligned) */
> +	bbt_info->bbt_size = nandi->blocks_per_device >> 2; /* 2 bits/block */
> +	bbt_buf_size = ALIGN(bbt_info->bbt_size, mtd->writesize);
> +	buf_size += bbt_buf_size + NANDI_BCH_DMA_ALIGNMENT;
> +
> +	/*	- BCH BUF list */
> +	buf_size += NANDI_BCH_BUF_LIST_SIZE + NANDI_BCH_DMA_ALIGNMENT;
> +
> +	/* Allocate bufffer */
> +	nandi->buf = devm_kzalloc(nandi->dev, buf_size, GFP_KERNEL);
> +	if (!nandi->buf) {
> +		dev_err(nandi->dev, "failed to allocate working buffers\n");
> +		return -ENOMEM;
> +	}
> +
> +	/* Set/Align buffer pointers */
> +	nandi->page_buf = PTR_ALIGN(nandi->buf, NANDI_BCH_DMA_ALIGNMENT);
> +	nandi->oob_buf  = nandi->page_buf + mtd->writesize;
> +	bbt_info->bbt   = PTR_ALIGN(nandi->oob_buf + mtd->oobsize,
> +				    NANDI_BCH_DMA_ALIGNMENT);
> +	nandi->buf_list = (uint32_t *)PTR_ALIGN(bbt_info->bbt + bbt_buf_size,
> +						NANDI_BCH_DMA_ALIGNMENT);
> +	nandi->cached_page = -1;
> +
> +	return 0;
> +}
> +
> +static int remap_named_resource(struct platform_device *pdev,
> +				char *name,
> +				void __iomem **io_ptr)
> +{
> +	struct resource *res, *mem;
> +	resource_size_t size;
> +	void __iomem *p;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, name);
> +	if (!res)
> +		return -ENXIO;
> +
> +	size = resource_size(res);
> +
> +	mem = devm_request_mem_region(&pdev->dev, res->start, size, name);
> +	if (!mem)
> +		return -EBUSY;
> +
> +	p = devm_ioremap_nocache(&pdev->dev, res->start, size);
> +	if (!p)
> +		return -ENOMEM;

Can you use devm_ioremap_resource() for the above several lines? So:

	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, name);
	*io_ptr = devm_ioremap_resource(&pdev->dev, res);
	if (IS_ERR(*io_ptr))
		return PTR_ERR(*io_ptr);
> +
> +	*io_ptr = p;
> +
> +	return 0;
> +}
> +
> +static struct nandi_controller *
> +nandi_init_resources(struct platform_device *pdev)
> +{
> +	struct stm_nand_bch_ddata *ddata = platform_get_drvdata(pdev);
> +	struct nandi_controller *nandi;
> +	int irq;
> +	int err;
> +
> +	nandi = devm_kzalloc(&pdev->dev, sizeof(*nandi), GFP_KERNEL);
> +	if (!nandi) {
> +		dev_err(&pdev->dev,
> +			"failed to allocate NANDi controller data\n");
> +		return ERR_PTR(-ENOMEM);
> +	}
> +
> +	nandi->dev = &pdev->dev;
> +
> +	err = remap_named_resource(pdev, "emi_nand", &nandi->base);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	err = remap_named_resource(pdev, "emiss", &nandi->emiss);
> +	if (err)
> +		return ERR_PTR(err);
> +
> +	nandi->dma = nandi->emiss + EMISS_NAND_DMA;
> +	nandi->emisscfg = nandi->emiss + EMISS_CFG;
> +
> +	irq = platform_get_irq_byname(pdev, "nand_irq");
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "failed to find IRQ resource\n");
> +		return ERR_PTR(irq);
> +	}
> +
> +	err = devm_request_irq(&pdev->dev, irq, nandi_irq_handler,
> +			       IRQF_DISABLED, dev_name(&pdev->dev), nandi);
> +	if (err) {
> +		dev_err(&pdev->dev, "irq request failed\n");
> +		return ERR_PTR(err);
> +	}
> +
> +	nandi->emi_clk = nandi_clk_setup(nandi, "emi");
> +	nandi->bch_clk = nandi_clk_setup(nandi, "bch");
> +
> +	ddata->nandi = nandi;
> +
> +	return nandi;
> +}
> +
> +static void *stm_bch_dt_get_ddata(struct platform_device *pdev)
> +{
> +	struct device_node *np = pdev->dev.of_node;
> +	struct stm_nand_bch_ddata *ddata;
> +	int ecc_strength;
> +	int ret;
> +
> +	ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
> +	if (!ddata)
> +		return ERR_PTR(-ENOMEM);
> +
> +	ecc_strength = of_get_nand_ecc_strength(np);
> +	if (ecc_strength == 0)
> +		ddata->bch_ecc_cfg = BCH_NO_ECC;
> +	else if (ecc_strength == 18)
> +		ddata->bch_ecc_cfg = BCH_18BIT_ECC;
> +	else if (ecc_strength == 30)
> +		ddata->bch_ecc_cfg = BCH_30BIT_ECC;
> +	else
> +		ddata->bch_ecc_cfg = BCH_ECC_AUTO;
> +
> +	ret = stm_of_get_nand_banks(&pdev->dev, np, &ddata->bank);
> +	if (ret < 0)
> +		return ERR_PTR(ret);
> +
> +	return ddata;
> +}
> +
> +static int stm_nand_bch_probe(struct platform_device *pdev)
> +{
> +	const char *part_probes[] = { "cmdlinepart", "ofpart", NULL, };

I feel like I already mentioned this, but maybe that was a different
driver: you're just using the defaults (see default_mtd_part_types /
parse_mtd_partitions) so you don't need to supply this array. Just pass
NULL to mtd_device_parse_register().

> +	struct device_node *np = pdev->dev.of_node;
> +	struct mtd_part_parser_data ppdata;
> +	struct stm_nand_bch_ddata *ddata;
> +	struct stm_nand_bank_data *bank;
> +	struct nandi_bbt_info *bbt_info;
> +	struct nandi_controller *nandi;
> +	struct nandi_info *info;
> +	struct nand_chip *chip;
> +	struct mtd_info *mtd;
> +	int compatible, err;
> +
> +	if (!np) {
> +		dev_err(&pdev->dev, "DT node found\n");

s/DT node found/DT node not found/

> +		return -EINVAL;
> +	}
> +
> +	ddata = stm_bch_dt_get_ddata(pdev);
> +	if (IS_ERR(ddata))
> +		return PTR_ERR(ddata);
> +
> +	ppdata.of_node = stm_of_get_partitions_node(np, 0);
> +
> +	platform_set_drvdata(pdev, ddata);
> +
> +	nandi = nandi_init_resources(pdev);
> +	if (IS_ERR(nandi)) {
> +		dev_err(&pdev->dev, "failed to initialise NANDi resources\n");
> +		return PTR_ERR(nandi);
> +	}
> +
> +	init_completion(&nandi->seq_completed);
> +	init_completion(&nandi->rbn_completed);
> +
> +	bank = ddata->bank;
> +	if (bank)
> +		nandi_init_controller(nandi, bank->csn);
> +
> +	info            = &nandi->info;
> +	chip            = &info->chip;
> +	bbt_info        = &info->bbt_info;
> +	mtd             = &info->mtd;
> +	mtd->priv       = chip;
> +	mtd->name       = dev_name(&pdev->dev);
> +	mtd->dev.parent = &pdev->dev;
> +
> +	nandi_set_mtd_defaults(nandi, mtd, chip);
> +
> +	err = nand_scan_ident(mtd, 1, NULL);
> +	if (err)
> +		return err;
> +
> +	/*
> +	 * Configure timing registers
> +	 */
> +	if (bank && bank->timing_spec) {

It looks like no one actually sets the 'timing_spec' field any more,
since you're not getting this info from the device tree any more. Should
you kill it (and this condition branch)?

> +		dev_info(&pdev->dev, "Using platform timing data\n");
> +		nandi_configure_timing_registers(nandi, bank->timing_spec,
> +						 bank->timing_relax);
> +	} else if (chip->onfi_version) {
> +		int mode = fls(onfi_get_async_timing_mode(chip) - 1);
> +		const struct nand_sdr_timings *spec =
> +			onfi_async_timing_mode_to_sdr_timings(mode);
> +
> +		/* Modes 4 and 5 (EDO) are not supported on our H/W */
> +		if (mode > 3)
> +			mode = 3;
> +
> +		dev_info(&pdev->dev, "Using ONFI Timing Mode %d\n", mode);
> +		nandi_configure_timing_registers(nandi,	spec,
> +					bank ? bank->timing_relax : 0);
> +	} else {
> +		dev_warn(&pdev->dev, "No timing data available\n");
> +	}
> +
> +	if (mtd->writesize < NANDI_BCH_SECTOR_SIZE) {
> +		dev_err(nandi->dev,
> +			"page size incompatible with BCH ECC sector\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Derive some working variables */
> +	nandi->sectors_per_page = mtd->writesize / NANDI_BCH_SECTOR_SIZE;
> +	nandi->blocks_per_device = mtd->size >> chip->phys_erase_shift;
> +	nandi->extra_addr = ((chip->chipsize >> chip->page_shift) >
> +			     0x10000) ? true : false;
> +	mtd->writebufsize = mtd->writesize;

Kill this line. That's nand_base.c's job (nand_scan_tail()).

> +
> +	/* Set ECC mode */
> +	if (ddata->bch_ecc_cfg == BCH_ECC_AUTO) {
> +		err = bch_set_ecc_auto(nandi, mtd);
> +		if (err) {
> +			dev_err(nandi->dev, "insufficient OOB for BCH ECC\n");
> +			return err;
> +		}
> +	} else {
> +		nandi->bch_ecc_mode = ddata->bch_ecc_cfg;
> +	}
> +
> +	chip->ecc.size = NANDI_BCH_SECTOR_SIZE;
> +	chip->ecc.bytes = mtd->oobsize;

While ecc.bytes is not actually used in a meaningful way for your
driver (with HWECC), this looks wrong. ecc.bytes should align with this
code from nand_base.c:

        /*
         * Set the number of read / write steps for one page depending on ECC
         * mode.
         */
        ecc->steps = mtd->writesize / ecc->size;
        if (ecc->steps * ecc->size != mtd->writesize) {
                pr_warn("Invalid ECC parameters\n");
                BUG();
        }
        ecc->total = ecc->steps * ecc->bytes;

Currently, it looks like ecc->total will be larger than oobsize, which
doesn't really make sense.

(Maybe we need a new WARN_ON(ecc->total > mtd->oobsize) in
nand_scan_tail()?)

> +	chip->ecc.strength = bch_ecc_strength[nandi->bch_ecc_mode];
> +
> +	info->ecclayout.eccbytes =
> +		nandi->sectors_per_page * bch_ecc_sizes[nandi->bch_ecc_mode];
> +
> +	compatible = bch_check_compatibility(nandi, mtd, chip);
> +	if (!compatible) {
> +		dev_err(nandi->dev,
> +			"NAND device incompatible with NANDi/BCH Controller\n");
> +		return -EINVAL;
> +	}
> +
> +	/* Tune BCH programs according to device found and ECC mode */
> +	bch_configure_progs(nandi);
> +
> +	err = nandi_init_working_buffers(nandi, bbt_info, mtd);
> +	if (err)
> +		return err;
> +
> +	err = nand_scan_tail(mtd);
> +	if (err)
> +		return err;
> +
> +#ifdef CONFIG_MTD_NAND_STM_BCH_BBT
> +	nandi_dump_bad_blocks(nandi);
> +#endif
> +	/* Add partitions */
> +	return mtd_device_parse_register(mtd, part_probes, &ppdata,
> +					 bank ? bank->partitions : NULL,
> +					 bank ? bank->nr_partitions : 0);
> +}
> +
> +static int stm_nand_bch_remove(struct platform_device *pdev)
> +{
> +	struct stm_nand_bch_ddata *ddata = platform_get_drvdata(pdev);
> +	struct nandi_controller *nandi = ddata->nandi;
> +
> +	nand_release(&nandi->info.mtd);
> +
> +	nandi_clk_disable(nandi);
> +
> +	return 0;
> +}
> +
> +static int stm_nand_bch_suspend(struct device *dev)
> +{
> +	struct stm_nand_bch_ddata *ddata = dev_get_drvdata(dev);
> +	struct nandi_controller *nandi = ddata->nandi;
> +
> +	nandi_clk_disable(nandi);
> +
> +	return 0;
> +}
> +static int stm_nand_bch_resume(struct device *dev)
> +{
> +	struct stm_nand_bch_ddata *ddata = dev_get_drvdata(dev);
> +	struct nandi_controller *nandi = ddata->nandi;
> +
> +	nandi_clk_enable(nandi);
> +
> +	return 0;
> +}
> +
> +static SIMPLE_DEV_PM_OPS(stm_nand_bch_pm_ops,
> +			 stm_nand_bch_suspend,
> +			 stm_nand_bch_resume);
> +
> +static struct of_device_id nand_bch_match[] = {
> +	{ .compatible = "st,nand-bch", },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, nand_bch_match);
> +
> +static struct platform_driver stm_nand_bch_driver = {
> +	.probe	= stm_nand_bch_probe ,
> +	.remove	= stm_nand_bch_remove,
> +	.driver	= {
> +		.name	= "stm-nand-bch",
> +		.owner	= THIS_MODULE,
> +		.of_match_table = of_match_ptr(nand_bch_match),
> +		.pm	= &stm_nand_bch_pm_ops,
> +	},
> +};
> +module_platform_driver(stm_nand_bch_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Angus Clark");
> +MODULE_DESCRIPTION("STM NAND BCH driver");
> diff --git a/drivers/mtd/nand/stm_nand_dt.c b/drivers/mtd/nand/stm_nand_dt.c
> new file mode 100644
> index 0000000..9facad6
> --- /dev/null
> +++ b/drivers/mtd/nand/stm_nand_dt.c
> @@ -0,0 +1,110 @@
> +/*
> + * drivers/mtd/nand/stm_nand_dt.c
> + *
> + * Support for NANDi BCH Controller Device Tree component
> + *
> + * Copyright (c) 2014 STMicroelectronics Limited
> + * Author: Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>

Double the author, double the fun! Might fix this if you get a chance.

> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#include <linux/init.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/err.h>
> +#include <linux/byteorder/generic.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_mtd.h>
> +#include <linux/mtd/nand.h>
> +#include <linux/mtd/stm_nand.h>
> +
> +#include "stm_nand_dt.h"
> +#include "stm_nand_regs.h"
> +
> +/**
> +* stm_of_get_partitions_node - get partitions node from stm-nand type devices.
> +*
> +* @dev		device pointer to use for devm allocations.
> +* @np		device node of the driver.
> +* @bank_nr	which bank number to use to get partitions.
> +*
> +* Returns a node pointer if found, with refcount incremented, use
> +* of_node_put() on it when done.
> +*
> +*/
> +struct device_node *stm_of_get_partitions_node(struct device_node *np,
> +					       int bank_nr)
> +{
> +	struct device_node *banknp, *partsnp = NULL;
> +	char name[10];
> +
> +	sprintf(name, "bank%d", bank_nr);
> +	banknp = of_get_child_by_name(np, name);
> +	if (banknp)
> +		return NULL;
> +
> +	partsnp = of_get_child_by_name(banknp, "partitions");
> +	of_node_put(banknp);
> +
> +	return partsnp;
> +}
> +EXPORT_SYMBOL(stm_of_get_partitions_node);

If you follow my advice on the DT binding structure, you don't need this
helper function at all.

> +
> +/**
> + * stm_of_get_nand_banks - Get nand banks info from a given device node.
> + *
> + * @dev			device pointer to use for devm allocations.
> + * @np			device node of the driver.
> + * @banksptr		double pointer to banks which is allocated
> + *			and filled with bank data.
> + *
> + * Returns a count of banks found in the given device node.
> + *
> + */
> +int stm_of_get_nand_banks(struct device *dev, struct device_node *np,
> +			  struct stm_nand_bank_data **banksptr)
> +{
> +	struct stm_nand_bank_data *banks;
> +	struct device_node *banknp;
> +	int nr_banks = 0;
> +
> +	if (!np)
> +		return -ENODEV;
> +
> +	nr_banks = of_get_child_count(np);
> +	if (!nr_banks) {
> +		dev_err(dev, "No NAND banks specified in DT: %s\n",
> +		np->full_name);
> +		return -EINVAL;
> +	}
> +
> +	*banksptr = devm_kzalloc(dev, sizeof(*banks) * nr_banks, GFP_KERNEL);

Missing an OOM check here.

> +	banks = *banksptr;
> +	banknp = NULL;

Is this initialization necessary? You overwrite it with the
for_each_child_of_node() loop.

> +
> +	for_each_child_of_node(np, banknp) {

If you change the DT binding to require a proper compatible property,
you'll need of_device_is_compatible() here.

Also, might the for_each_available_child_of_node() helper be preferable,
so you will properly ignore any "disabled" nodes, if they exist?

> +		int bank = 0;
> +
> +		of_property_read_u32(banknp, "st,nand-csn", &banks[bank].csn);
> +
> +		if (of_get_nand_bus_width(banknp) == 16)
> +			banks[bank].options |= NAND_BUSWIDTH_16;
> +		if (of_get_nand_on_flash_bbt(banknp))
> +			banks[bank].bbt_options |= NAND_BBT_USE_FLASH;
> +
> +		banks[bank].nr_partitions = 0;
> +		banks[bank].partitions = NULL;
> +
> +		of_property_read_u32(banknp, "st,nand-timing-relax",
> +				     &banks[bank].timing_relax);
> +		bank++;
> +	}
> +
> +	return nr_banks;
> +}
> +EXPORT_SYMBOL(stm_of_get_nand_banks);
> diff --git a/drivers/mtd/nand/stm_nand_dt.h b/drivers/mtd/nand/stm_nand_dt.h
> new file mode 100644
> index 0000000..0d2b920
> --- /dev/null
> +++ b/drivers/mtd/nand/stm_nand_dt.h
> @@ -0,0 +1,24 @@
> +/*
> + * drivers/mtd/nand/stm_nand_dt.h
> + *
> + * Support for NANDi BCH Controller Device Tree component
> + *
> + * Copyright (c) 2014 STMicroelectronics Limited
> + * Author: Author: Srinivas Kandagatla <srinivas.kandagatla@st.com>

Author: Author: again

> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#ifndef STM_NAND_DT_H
> +#define STM_NAND_DT_H
> +
> +struct device_node *stm_of_get_partitions_node(struct device_node *np,
> +					       int bank_nr);
> +
> +int stm_of_get_nand_banks(struct device *dev, struct device_node *np,
> +				 struct stm_nand_bank_data **banksp);

Hmm, really only two functions? And one of those might be not be needed,
as I commented above. I don't think you need a separate *_dt.{c,h} file.
Please merge the two.

> +
> +#endif /* STM_NAND_DT_H */
> diff --git a/include/linux/mtd/stm_nand.h b/include/linux/mtd/stm_nand.h
> new file mode 100644
> index 0000000..c3c805f
> --- /dev/null
> +++ b/include/linux/mtd/stm_nand.h
> @@ -0,0 +1,147 @@
> +/*
> + * include/linux/mtd/stm_mtd.h
> + *
> + * Support for STMicroelectronics NAND Controllers
> + *
> + * Copyright (c) 2014 STMicroelectronics Limited
> + * Author: Angus Clark <Angus.Clark@st.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#ifndef __LINUX_STM_NAND_H
> +#define __LINUX_STM_NAND_H
> +
> +#include <linux/io.h>
> +#include <linux/mtd/nand.h>
> +
> +/* ECC Modes */
> +enum stm_nand_bch_ecc_config {
> +	BCH_18BIT_ECC = 0,
> +	BCH_30BIT_ECC,
> +	BCH_NO_ECC,
> +	BCH_ECC_RSRV,
> +	BCH_ECC_AUTO,
> +};
> +
> +/* Bad Block Table (BBT) */
> +struct nandi_bbt_info {
> +	uint32_t	bbt_size;		/* Size of bad-block table */
> +	uint32_t	bbt_vers[2];		/* Version (Primary/Mirror) */
> +	uint32_t	bbt_block[2];		/* Block No. (Primary/Mirror) */
> +	uint8_t		*bbt;			/* Table data */
> +};
> +
> +/* Collection of MTD/NAND device information */
> +struct nandi_info {
> +	struct mtd_info		mtd;		/* MTD info */
> +	struct nand_chip	chip;		/* NAND chip info */
> +
> +	struct nand_ecclayout	ecclayout;	/* MTD ECC layout */
> +	struct nandi_bbt_info	bbt_info;	/* Bad Block Table */
> +	int			nr_parts;	/* Number of MTD partitions */
> +	struct	mtd_partition	*parts;		/* MTD partitions */
> +};
> +
> +/* NANDi Controller (Hamming/BCH) */
> +struct nandi_controller {
> +	void __iomem		*base;		/* Controller base*/
> +	void __iomem		*emiss;		/* EMISS control base */
> +	void __iomem		*emisscfg;	/* EMISS config base */
> +	void __iomem		*dma;		/* DMA control base */
> +
> +	struct clk		*bch_clk;
> +	struct clk		*emi_clk;
> +						/* IRQ-triggered Completions: */
> +	struct completion	seq_completed;	/*   SEQ Over */
> +	struct completion	rbn_completed;	/*   RBn */
> +
> +	struct device		*dev;
> +
> +	int			bch_ecc_mode;	/* ECC mode */
> +	bool			extra_addr;	/* Extra address cycle */
> +
> +	uint32_t		blocks_per_device;
> +	uint32_t		sectors_per_page;
> +
> +	uint8_t			*buf;		/* Some buffers to use */
> +	uint8_t			*page_buf;
> +	uint8_t			*oob_buf;
> +	uint32_t		*buf_list;
> +
> +	int			cached_page;	/* page number of page in */
> +						/* 'page_buf'             */

You never use this field, except to set it to '-1'. Perhaps kill it? I
doubt you actually will win much by trying to cache pages at the driver
level anyway. It's pretty easy to get wrong too.

> +
> +	struct nandi_info	info;		/* NAND device info */
> +};
> +
> +/*
> + * Board-level specification relating to a 'bank' of NAND Flash
> + */
> +struct stm_nand_bank_data {
> +	int			csn;
> +	int			nr_partitions;
> +	struct mtd_partition	*partitions;
> +	unsigned int		options;
> +	unsigned int		bbt_options;
> +
> +	struct nand_sdr_timings *timing_spec;
> +
> +	/*
> +	 * No. of IP clk cycles by which to 'relax' the timing configuration.
> +	 * Required on some boards to to accommodate board-level limitations.
> +	 * Used in conjunction with 'nand_sdr_timings' and ONFI configuration.
> +	 */
> +	int			timing_relax;
> +};
> +
> +struct stm_nand_bch_ddata {
> +	struct nandi_controller *nandi;
> +	struct stm_nand_bank_data *bank;
> +	enum stm_nand_bch_ecc_config bch_ecc_cfg;
> +};
> +
> +enum nandi_controllers {
> +	STM_NANDI_UNCONFIGURED,
> +	STM_NANDI_HAMMING,
> +	STM_NANDI_BCH
> +};
> +
> +extern int flex_read_raw(struct nandi_controller *nandi,
> +			 uint32_t page_addr,
> +			 uint32_t col_addr,
> +			 uint8_t *buf, uint32_t len);
> +extern uint8_t bch_write_page(struct nandi_controller *nandi,
> +			      loff_t offs, const uint8_t *buf);
> +extern uint8_t bch_erase_block(struct nandi_controller *nandi,
> +			       loff_t offs);
> +extern int bch_read_page(struct nandi_controller *nandi,
> +			 loff_t offs, uint8_t *buf);

This isn't exactly what I had in mind when I suggested the BBT
implementation be separated from the NAND driver. I don't expect a
driver to export its internal functions so that the BBT code can link to
them. I expect the BBT implementation to use indirected versions.

Particularly, we already had discussion of using the mtd_*() API
helpers, although there was some conflicting opinion there. At a
minimum, I think your BBT driver can use the nand_chip function
callbacks.

Basically, I think most / all of this header could be disintegrated and
each driver be written in a more modular fashion. But anyway, if you
take the first step of removing these exported functions, I think we can
live with the rest.

> +
> +#define EMISS_NAND_CONFIG_HAMMING_NOT_BCH 	(0x1 << 6)
> +
> +static inline void emiss_nandi_select(struct nandi_controller *nandi,
> +				      enum nandi_controllers controller)
> +{
> +	unsigned v;
> +
> +	v = readl(nandi->emisscfg);
> +
> +	if (controller == STM_NANDI_HAMMING) {
> +		if (v & EMISS_NAND_CONFIG_HAMMING_NOT_BCH)
> +			return;
> +		v |= EMISS_NAND_CONFIG_HAMMING_NOT_BCH;
> +	} else {
> +		if (!(v & EMISS_NAND_CONFIG_HAMMING_NOT_BCH))
> +			return;
> +		v &= ~EMISS_NAND_CONFIG_HAMMING_NOT_BCH;
> +	}
> +
> +	writel(v, nandi->emisscfg);
> +	readl(nandi->emisscfg);
> +}

Any particular reason this function is in the header? It's only used in
one file.

> +
> +#endif /* __LINUX_STM_NAND_H */

Brian

[1] http://lists.infradead.org/pipermail/linux-mtd/2014-July/054500.html
[2] http://lists.infradead.org/pipermail/linux-mtd/2014-July/054881.html
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On Wed, Aug 27, 2014 at 01:42:23PM +0100, Lee Jones wrote:
> Reviewed-By: Pekon Gupta <pekon@pek-sem.com>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/mtd/nand/Kconfig        |    7 +
>  drivers/mtd/nand/Makefile       |    1 +
>  drivers/mtd/nand/stm_nand_bch.c | 1616 +++++++++++++++++++++++++++++++++++++++
>  drivers/mtd/nand/stm_nand_dt.c  |  110 +++
>  drivers/mtd/nand/stm_nand_dt.h  |   24 +
>  include/linux/mtd/stm_nand.h    |  147 ++++
>  6 files changed, 1905 insertions(+)
>  create mode 100644 drivers/mtd/nand/stm_nand_bch.c
>  create mode 100644 drivers/mtd/nand/stm_nand_dt.c
>  create mode 100644 drivers/mtd/nand/stm_nand_dt.h
>  create mode 100644 include/linux/mtd/stm_nand.h

One more thing: you never answered my question from [1]: 

Does your driver pass the MTD tests? (drivers/mtd/tests/)

Brian

[1] http://lists.infradead.org/pipermail/linux-mtd/2014-August/055084.html
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On Sun, 05 Oct 2014, Brian Norris wrote:

> On Wed, Aug 27, 2014 at 01:42:23PM +0100, Lee Jones wrote:
> > Reviewed-By: Pekon Gupta <pekon@pek-sem.com>
> > Signed-off-by: Lee Jones <lee.jones@linaro.org>
> > ---
> >  drivers/mtd/nand/Kconfig        |    7 +
> >  drivers/mtd/nand/Makefile       |    1 +
> >  drivers/mtd/nand/stm_nand_bch.c | 1616 +++++++++++++++++++++++++++++++++++++++
> >  drivers/mtd/nand/stm_nand_dt.c  |  110 +++
> >  drivers/mtd/nand/stm_nand_dt.h  |   24 +
> >  include/linux/mtd/stm_nand.h    |  147 ++++
> >  6 files changed, 1905 insertions(+)
> >  create mode 100644 drivers/mtd/nand/stm_nand_bch.c
> >  create mode 100644 drivers/mtd/nand/stm_nand_dt.c
> >  create mode 100644 drivers/mtd/nand/stm_nand_dt.h
> >  create mode 100644 include/linux/mtd/stm_nand.h
> 
> One more thing: you never answered my question from [1]: 
> 
> Does your driver pass the MTD tests? (drivers/mtd/tests/)

It does.  Apart from the ones which insist on reading the OOB area,
which isn't allowed via the normal call-backs supplied.

> [1] http://lists.infradead.org/pipermail/linux-mtd/2014-August/055084.html

> First off, this patch has several checkpatch warnings, some of which
> should be addressed:

Fixed.

> > +/* ONFI define 6 timing modes */
> > +#define ST_NAND_ONFI_TIMING_MODES		6
> 
> This is unused?

Removed.

[...]

> > +static inline void bch_load_prog_cpu(struct nandi_controller *nandi,
> > +				     struct bch_prog *prog)
> > +{
> > +	void __iomem *dst = nandi->base + NANDBCH_ADDRESS_REG_1;
> > +	uint32_t *src = (uint32_t *)prog;
> > +	int i;
> > +
> > +	for (i = 0; i < 16; i++) {
> > +		/* Skip registers marked as "reserved" */
> > +		if (i != 11 && i != 14)
> > +			writel(*src, dst);
> > +		src++;
> > +		dst += sizeof(uint32_t *);
> 
> Are you sure you want to base the increment on the pointer size? This
> looks like it might break if ever used on a 64-bit architecture. You're
> probably just looking for a constant 4, or maybe sizeof(u32).

Fixed

[...]

> > +static int check_erased_page(uint8_t *data, uint32_t page_size, int max_zeros)
> > +{
> > +	uint8_t *b = data;
> > +	int zeros = 0;
> > +	int i;
> > +
> > +	for (i = 0; i < page_size; i++) {
> > +		zeros += hweight8(~*b++);
> > +		if (zeros > max_zeros)
> > +			return -1;
> > +	}
> > +
> > +	if (zeros)
> > +		memset(data, 0xff, page_size);
> > +
> > +	return zeros;
> > +}
> 
> I pointed out some flaws in this function back in July [1]. You said
> you'd look into this one [2]. I really don't want to accept yet another
> custom, unsound erased-page check if at all possible.

That's not quite true.  I said that I think it doesn't matter about
not taking the OOB area into consideration, which I still believe is
the case.  This controller does not allow access into the OOB area.

> > +/* Returns the number of ECC errors, or '-1' for uncorrectable error */
> > +int bch_read_page(struct nandi_controller *nandi,
> > +		  loff_t offs,
> > +		  uint8_t *buf)
> > +{
> > +	struct nand_chip *chip = &nandi->info.chip;
> > +	struct bch_prog *prog = &bch_prog_read_page;
> > +	uint32_t page_size = nandi->info.mtd.writesize;
> > +	unsigned long list_phys;
> 
> Please use dma_addr_t. This is an intentionally opaque (to some degree)
> type.
> 
> > +	unsigned long buf_phys;
> 
> Ditto.
> 
> BTW, is your hardware actually restricted to a 32-bit address space? If
> it has some expanded registers for larger physical address ranges, it'd
> be good to handle the upper bits of the DMA address when mapping. Or
> else, it would be good to reflect this in your driver with
> dma_set_mask() I think.

Yes, it's 32bit only.  I will add a call to dma_set_mask() to reflect
this.

... or not.  See below.

> > +	uint32_t ecc_err;
> > +	int ret = 0;
> > +
> > +	dev_dbg(nandi->dev, "%s: offs = 0x%012llx\n", __func__, offs);
> > +
> > +	BUG_ON(offs & (NANDI_BCH_DMA_ALIGNMENT - 1));
> > +
> > +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> > +
> > +	nandi_enable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> > +	reinit_completion(&nandi->seq_completed);
> > +
> > +	/* Reset ECC stats */
> > +	writel(CFG_RESET_ECC_ALL | CFG_ENABLE_AFM,
> > +	       nandi->base + NANDBCH_CONTROLLER_CFG);
> > +	writel(CFG_ENABLE_AFM, nandi->base + NANDBCH_CONTROLLER_CFG);
> > +
> > +	prog->addr = (uint32_t)((offs >> (chip->page_shift - 8)) & 0xffffff00);
> > +
> > +	buf_phys = dma_map_single(NULL, buf, page_size, DMA_FROM_DEVICE);
> 
> Why NULL for the first arg? You should use the proper device (which will
> help with the 32-bit / 64-bit masking, I think.
> 
> Also, dma_map_single() can fail. It's good practice to check the return
> value with dma_mapping_error(). Same in a few other places.

If you do not supply the first parameter here, it falls back to
arm_dma_ops, which is what we want.  I guess this is also why we do
not have to set the DMA mask, as we're running on ARM32, rather than
AARCH64.

> > +	memset(nandi->buf_list, 0x00, NANDI_BCH_BUF_LIST_SIZE);
> > +	nandi->buf_list[0] = buf_phys | (nandi->sectors_per_page - 1);
> > +
> > +	list_phys = dma_map_single(NULL, nandi->buf_list,
> > +				   NANDI_BCH_BUF_LIST_SIZE, DMA_TO_DEVICE);

Fixed.

> > +
> > +	writel(list_phys, nandi->base + NANDBCH_BUFFER_LIST_PTR);
> > +
> > +	bch_load_prog_cpu(nandi, prog);
> > +
> > +	bch_wait_seq(nandi);
> > +
> > +	nandi_disable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> > +
> > +	dma_unmap_single(NULL, list_phys, NANDI_BCH_BUF_LIST_SIZE,
> > +			 DMA_TO_DEVICE);
> > +	dma_unmap_single(NULL, buf_phys, page_size, DMA_FROM_DEVICE);
> > +
> > +	/* Use the maximum per-sector ECC count! */
> > +	ecc_err = readl(nandi->base + NANDBCH_ECC_SCORE_REG_A) & 0xff;
> > +	if (ecc_err == 0xff) {
> > +		/*
> > +		 * Downgrade uncorrectable ECC error for an erased page,
> > +		 * tolerating 'bch_ecc_strength' bits at zero.
> > +		 */
> > +		ret = check_erased_page(buf, page_size, chip->ecc.strength);
> 
> I commented in [1] that you don't want to use the full ECC strength
> here.

Actually I took your first suggestion:

  "Couldn't this (more straightforwarly) just be chip->ecc.strength?"

... but I have now fixed it up to blindly /2 instead.

[...]

> > +static int bch_read(struct mtd_info *mtd, struct nand_chip *chip,
> > +			 uint8_t *buf, int oob_required, int page)
> > +{
> > +	struct nandi_controller *nandi = chip->priv;
> > +	uint32_t page_size = mtd->writesize;
> > +	loff_t offs = (loff_t)page * page_size;
> > +	bool bounce = false;
> > +	uint8_t *p;
> > +	int ret;
> > +
> > +	if (((unsigned int)buf & (NANDI_BCH_DMA_ALIGNMENT - 1)) ||
> > +	    (!virt_addr_valid(buf))) /* vmalloc'd buffer! */
> 
> If you really need this custom DMA check, can you at least make it the
> same as in bch_write_page(), and put it in a common macro / static
> inline function?

We absolutely do need it, as the buffers which the framework currently
provide are seldom 64 Byte aligned.  I will provide a static inline
function as requested.

[...]

> > +static int bch_mtd_read_oob(struct mtd_info *mtd,
> > +			    struct nand_chip *chip, int page)
> > +{
> > +	BUG();
> 
> Are you sure this can't be implemented, even if it's not the expected
> mode of operation? That's really unforunate.

It can.  We have a 'special' function for it using the extended
flexible mode.  Trying to upstream this has been hard enough already,
without more crud to deal with.  I will hopefully be adding this
functionality as small, succinct patches subsequently.

> > +	return 0;
> > +}
> > +
> > +static int bch_mtd_write_oob(struct mtd_info *mtd,
> > +			     struct nand_chip *chip, int page)
> > +{
> > +	BUG();
> 
> Same question.

Same answer.

> > +	return 0;
> > +}
> > +
> > +static int bch_read_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
> > +			     uint8_t *buf, int oob_required, int page)
> > +{
> > +	BUG();
> 
> Same question.

Same answer.

> > +	return 0;
> > +}
> > +
> > +static int bch_write_page_raw(struct mtd_info *mtd, struct nand_chip *chip,
> > +			      const uint8_t *buf, int oob_required)
> > +{
> > +	BUG();
> 
> Same question.

Same answer.

> > +	return 0;
> > +}

[...]

> > +#ifdef CONFIG_MTD_NAND_STM_BCH_BBT
> 
> This #ifdef won't work right when you build the BBT code as a module.
> You may need IS_ENABLED(), and you'll have to ensure you can't make this
> driver built-in while the BBT code is a module.
> 
> One option: just disallow building your BBT code as a module.

Done.

[...]

> > +static int remap_named_resource(struct platform_device *pdev,
> > +				char *name,
> > +				void __iomem **io_ptr)
> > +{
> > +	struct resource *res, *mem;
> > +	resource_size_t size;
> > +	void __iomem *p;
> > +
> > +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, name);
> > +	if (!res)
> > +		return -ENXIO;
> > +
> > +	size = resource_size(res);
> > +
> > +	mem = devm_request_mem_region(&pdev->dev, res->start, size, name);
> > +	if (!mem)
> > +		return -EBUSY;
> > +
> > +	p = devm_ioremap_nocache(&pdev->dev, res->start, size);
> > +	if (!p)
> > +		return -ENOMEM;
> 
> Can you use devm_ioremap_resource() for the above several lines? So:
> 
> 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, name);
> 	*io_ptr = devm_ioremap_resource(&pdev->dev, res);
> 	if (IS_ERR(*io_ptr))
> 		return PTR_ERR(*io_ptr);

I've been staring at this file so long now I'm missing the simple
stuff.  This is of course the new and improved way of doing this
stuff.  I will update.

[...]

> > +static int stm_nand_bch_probe(struct platform_device *pdev)
> > +{
> > +	const char *part_probes[] = { "cmdlinepart", "ofpart", NULL, };
> 
> I feel like I already mentioned this, but maybe that was a different
> driver: you're just using the defaults (see default_mtd_part_types /
> parse_mtd_partitions) so you don't need to supply this array. Just pass
> NULL to mtd_device_parse_register().

I don't recall you mentioning this before, but I could be wrong.

Now fixed.

[...]

> > +	/*
> > +	 * Configure timing registers
> > +	 */
> > +	if (bank && bank->timing_spec) {
> 
> It looks like no one actually sets the 'timing_spec' field any more,
> since you're not getting this info from the device tree any more. Should
> you kill it (and this condition branch)?

Looks that way.

Removed all mention of timing_spec.

[...]

> > +	chip->ecc.size = NANDI_BCH_SECTOR_SIZE;
> > +	chip->ecc.bytes = mtd->oobsize;
> 
> While ecc.bytes is not actually used in a meaningful way for your
> driver (with HWECC), this looks wrong. ecc.bytes should align with this
> code from nand_base.c:
> 
>         /*
>          * Set the number of read / write steps for one page depending on ECC
>          * mode.
>          */
>         ecc->steps = mtd->writesize / ecc->size;
>         if (ecc->steps * ecc->size != mtd->writesize) {
>                 pr_warn("Invalid ECC parameters\n");
>                 BUG();
>         }
>         ecc->total = ecc->steps * ecc->bytes;
> 
> Currently, it looks like ecc->total will be larger than oobsize, which
> doesn't really make sense.
> 
> (Maybe we need a new WARN_ON(ecc->total > mtd->oobsize) in
> nand_scan_tail()?)

[...]

> > +struct device_node *stm_of_get_partitions_node(struct device_node *np,
> > +					       int bank_nr)
> > +{
> > +	struct device_node *banknp, *partsnp = NULL;
> > +	char name[10];
> > +
> > +	sprintf(name, "bank%d", bank_nr);
> > +	banknp = of_get_child_by_name(np, name);
> > +	if (banknp)
> > +		return NULL;
> > +
> > +	partsnp = of_get_child_by_name(banknp, "partitions");
> > +	of_node_put(banknp);
> > +
> > +	return partsnp;
> > +}
> > +EXPORT_SYMBOL(stm_of_get_partitions_node);
> 
> If you follow my advice on the DT binding structure, you don't need this
> helper function at all.

It's gone.

> > +/**
> > + * stm_of_get_nand_banks - Get nand banks info from a given device node.
> > + *
> > + * @dev			device pointer to use for devm allocations.
> > + * @np			device node of the driver.
> > + * @banksptr		double pointer to banks which is allocated
> > + *			and filled with bank data.
> > + *
> > + * Returns a count of banks found in the given device node.
> > + *
> > + */
> > +int stm_of_get_nand_banks(struct device *dev, struct device_node *np,
> > +			  struct stm_nand_bank_data **banksptr)
> > +{
> > +	struct stm_nand_bank_data *banks;
> > +	struct device_node *banknp;
> > +	int nr_banks = 0;
> > +
> > +	if (!np)
> > +		return -ENODEV;
> > +
> > +	nr_banks = of_get_child_count(np);
> > +	if (!nr_banks) {
> > +		dev_err(dev, "No NAND banks specified in DT: %s\n",
> > +		np->full_name);
> > +		return -EINVAL;
> > +	}
> > +
> > +	*banksptr = devm_kzalloc(dev, sizeof(*banks) * nr_banks, GFP_KERNEL);
> 
> Missing an OOM check here.
> 
> > +	banks = *banksptr;
> > +	banknp = NULL;
> 
> Is this initialization necessary? You overwrite it with the
> for_each_child_of_node() loop.

Both fixed.

> > +	for_each_child_of_node(np, banknp) {
> 
> If you change the DT binding to require a proper compatible property,
> you'll need of_device_is_compatible() here.

I see no reason to allocate a compatible property to the bank
descriptors.  They're not being registered/actioned through
of_platform_populate(), so ...

> Also, might the for_each_available_child_of_node() helper be preferable,
> so you will properly ignore any "disabled" nodes, if they exist?

Right, good catch.

> > +		int bank = 0;
> > +
> > +		of_property_read_u32(banknp, "st,nand-csn", &banks[bank].csn);
> > +
> > +		if (of_get_nand_bus_width(banknp) == 16)
> > +			banks[bank].options |= NAND_BUSWIDTH_16;
> > +		if (of_get_nand_on_flash_bbt(banknp))
> > +			banks[bank].bbt_options |= NAND_BBT_USE_FLASH;
> > +
> > +		banks[bank].nr_partitions = 0;
> > +		banks[bank].partitions = NULL;
> > +
> > +		of_property_read_u32(banknp, "st,nand-timing-relax",
> > +				     &banks[bank].timing_relax);
> > +		bank++;
> > +	}
> > +
> > +	return nr_banks;
> > +}
> > +EXPORT_SYMBOL(stm_of_get_nand_banks);
> > diff --git a/drivers/mtd/nand/stm_nand_dt.h b/drivers/mtd/nand/stm_nand_dt.h
> > new file mode 100644
> > index 0000000..0d2b920
> > --- /dev/null
> > +++ b/drivers/mtd/nand/stm_nand_dt.h

[...]

> > +int stm_of_get_nand_banks(struct device *dev, struct device_node *np,
> > +				 struct stm_nand_bank_data **banksp);
> 
> Hmm, really only two functions? And one of those might be not be needed,
> as I commented above. I don't think you need a separate *_dt.{c,h} file.
> Please merge the two.

Now squashed.

[...]

> > +	int			cached_page;	/* page number of page in */
> > +						/* 'page_buf'             */
> 
> You never use this field, except to set it to '-1'. Perhaps kill it? I
> doubt you actually will win much by trying to cache pages at the driver
> level anyway. It's pretty easy to get wrong too.

Gone.

[...]

> > +extern int flex_read_raw(struct nandi_controller *nandi,
> > +			 uint32_t page_addr,
> > +			 uint32_t col_addr,
> > +			 uint8_t *buf, uint32_t len);
> > +extern uint8_t bch_write_page(struct nandi_controller *nandi,
> > +			      loff_t offs, const uint8_t *buf);
> > +extern uint8_t bch_erase_block(struct nandi_controller *nandi,
> > +			       loff_t offs);
> > +extern int bch_read_page(struct nandi_controller *nandi,
> > +			 loff_t offs, uint8_t *buf);
> 
> This isn't exactly what I had in mind when I suggested the BBT
> implementation be separated from the NAND driver. I don't expect a
> driver to export its internal functions so that the BBT code can link to
> them. I expect the BBT implementation to use indirected versions.
> 
> Particularly, we already had discussion of using the mtd_*() API
> helpers, although there was some conflicting opinion there. At a
> minimum, I think your BBT driver can use the nand_chip function
> callbacks.
> 
> Basically, I think most / all of this header could be disintegrated and
> each driver be written in a more modular fashion. But anyway, if you
> take the first step of removing these exported functions, I think we can
> live with the rest.

No longer exported.

> > +#define EMISS_NAND_CONFIG_HAMMING_NOT_BCH 	(0x1 << 6)
> > +
> > +static inline void emiss_nandi_select(struct nandi_controller *nandi,
> > +				      enum nandi_controllers controller)
> > +{
> > +	unsigned v;
> > +
> > +	v = readl(nandi->emisscfg);
> > +
> > +	if (controller == STM_NANDI_HAMMING) {
> > +		if (v & EMISS_NAND_CONFIG_HAMMING_NOT_BCH)
> > +			return;
> > +		v |= EMISS_NAND_CONFIG_HAMMING_NOT_BCH;
> > +	} else {
> > +		if (!(v & EMISS_NAND_CONFIG_HAMMING_NOT_BCH))
> > +			return;
> > +		v &= ~EMISS_NAND_CONFIG_HAMMING_NOT_BCH;
> > +	}
> > +
> > +	writel(v, nandi->emisscfg);
> > +	readl(nandi->emisscfg);
> > +}
> 
> Any particular reason this function is in the header? It's only used in
> one file.

Yes, there are potentially two other drivers (that hopefully some
other poor sap will try to upstream). :D

> > +#endif /* __LINUX_STM_NAND_H */
> 
> Brian
> 
> [1] http://lists.infradead.org/pipermail/linux-mtd/2014-July/054500.html
> [2] http://lists.infradead.org/pipermail/linux-mtd/2014-July/054881.html

On Thu, Oct 09, 2014 at 03:39:23PM +0100, Lee Jones wrote:
> > > +static int check_erased_page(uint8_t *data, uint32_t page_size, int max_zeros)
> > > +{
> > > +	uint8_t *b = data;
> > > +	int zeros = 0;
> > > +	int i;
> > > +
> > > +	for (i = 0; i < page_size; i++) {
> > > +		zeros += hweight8(~*b++);
> > > +		if (zeros > max_zeros)
> > > +			return -1;
> > > +	}
> > > +
> > > +	if (zeros)
> > > +		memset(data, 0xff, page_size);
> > > +
> > > +	return zeros;
> > > +}
> > 
> > I pointed out some flaws in this function back in July [1]. You said
> > you'd look into this one [2]. I really don't want to accept yet another
> > custom, unsound erased-page check if at all possible.
> 
> That's not quite true.  I said that I think it doesn't matter about
> not taking the OOB area into consideration, which I still believe is
> the case.  This controller does not allow access into the OOB area.

Perhaps I'm not being clear enough.

While the controller may not allow you to program the spare area
directly, you do so implicitly by allowing the controller to program BCH
parity bytes to the spare area, right? So when you want to check if the
page is blank, you have to consider ALL areas that will be used -- both
in-band and out-of-band.

So, I'll repeat my question and try to elaborate:

  "What if this is a mostly-blank page, with ECC data, but most of the
  bitflips are in the spare area? Then you will "correct" this page to
  all 0xFF, not noticing that this was really not a blank page at all."

More specifically:

  1. Suppose you program a page with just a single byte of non-0xff
  data, and your correction strength is at least 8 bits per sector

  2. When programming this page, your BCH controller writes parity bytes
  to the spare area

  3. Over time (a lot of reads, for example), suppose you develop a lot
  of bit flips in the spare area, such that your controller cannot
  correct them any longer

Now consider two algorithms:

  (A) Your current proposal, to just check the in-band data that you can
  easily access. If there are more than X zero-bits in the page, return
  an error. Otherwise, clear the page and log a correctable error.

  (B) My suggestion, to check both the in-band and out-of-band. Same as
  algorithm (A), except you check for X total zero-bits in both the
  in-band and out-of-band

In the scenario I described, algorithm A will only notice up to 8 zero
bits (in that single byte we programmed), so if X is greater than 8,
algorithm A will falsely declare this an erased page and silently
clobber the data we programmed to it.

Algorithm B would notice that there are many zero bits in the spare area
(due to the programmed parity bytes) and will correctly declare this a
corrupt, non-erased page.

If I've made any false assumptions in here, please point them out. But
otherwise, I'd say that any erased-page detection algorithm that ignores
the spare area is incorrect.

If you agree with me, then you have at least two options:

(1) Remove this erased page check entirely from the initial driver, with
    a TODO item to add spare area read support and to improve this
    algorithm

(2) Keep the check as-is, but put a large FIXME warning which notes why
    the algorithm is wrong. It's possible the wrong algorithm is still
    marginally better than no erased-page detection at all. I'm not sure
    what the probability distributions are like for this sort of error.

> > > +/* Returns the number of ECC errors, or '-1' for uncorrectable error */
> > > +int bch_read_page(struct nandi_controller *nandi,
> > > +		  loff_t offs,
> > > +		  uint8_t *buf)
> > > +{
> > > +	struct nand_chip *chip = &nandi->info.chip;
> > > +	struct bch_prog *prog = &bch_prog_read_page;
> > > +	uint32_t page_size = nandi->info.mtd.writesize;
> > > +	unsigned long list_phys;
> > 
> > Please use dma_addr_t. This is an intentionally opaque (to some degree)
> > type.
> > 
> > > +	unsigned long buf_phys;
> > 
> > Ditto.
> > 
> > BTW, is your hardware actually restricted to a 32-bit address space? If
> > it has some expanded registers for larger physical address ranges, it'd
> > be good to handle the upper bits of the DMA address when mapping. Or
> > else, it would be good to reflect this in your driver with
> > dma_set_mask() I think.
> 
> Yes, it's 32bit only.  I will add a call to dma_set_mask() to reflect
> this.
> 
> ... or not.  See below.
> 
> > > +	uint32_t ecc_err;
> > > +	int ret = 0;
> > > +
> > > +	dev_dbg(nandi->dev, "%s: offs = 0x%012llx\n", __func__, offs);
> > > +
> > > +	BUG_ON(offs & (NANDI_BCH_DMA_ALIGNMENT - 1));
> > > +
> > > +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> > > +
> > > +	nandi_enable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> > > +	reinit_completion(&nandi->seq_completed);
> > > +
> > > +	/* Reset ECC stats */
> > > +	writel(CFG_RESET_ECC_ALL | CFG_ENABLE_AFM,
> > > +	       nandi->base + NANDBCH_CONTROLLER_CFG);
> > > +	writel(CFG_ENABLE_AFM, nandi->base + NANDBCH_CONTROLLER_CFG);
> > > +
> > > +	prog->addr = (uint32_t)((offs >> (chip->page_shift - 8)) & 0xffffff00);
> > > +
> > > +	buf_phys = dma_map_single(NULL, buf, page_size, DMA_FROM_DEVICE);
> > 
> > Why NULL for the first arg? You should use the proper device (which will
> > help with the 32-bit / 64-bit masking, I think.
> > 
> > Also, dma_map_single() can fail. It's good practice to check the return
> > value with dma_mapping_error(). Same in a few other places.
> 
> If you do not supply the first parameter here, it falls back to
> arm_dma_ops, which is what we want.  I guess this is also why we do
> not have to set the DMA mask, as we're running on ARM32, rather than
> AARCH64.

I think it's standard practice to make your hardware limitations
explicit when writing a driver. From Documentation/DMA-API-HOWTO.txt
under "DMA addressing limitations":

  "It is good style to do this even if your device holds the default
  setting, because this shows that you did think about these issues wrt.
  your device."

But I won't press this issue.

> > > +static int bch_mtd_read_oob(struct mtd_info *mtd,
> > > +			    struct nand_chip *chip, int page)
> > > +{
> > > +	BUG();
> > 
> > Are you sure this can't be implemented, even if it's not the expected
> > mode of operation? That's really unforunate.
> 
> It can.  We have a 'special' function for it using the extended
> flexible mode.  Trying to upstream this has been hard enough already,
> without more crud to deal with.  I will hopefully be adding this
> functionality as small, succinct patches subsequently.

OK. But this is relevant to my points above -- particularly, you might
want the 'read OOB' functionality to properly implement the erased page
check.

> > > +	for_each_child_of_node(np, banknp) {
> > 
> > If you change the DT binding to require a proper compatible property,
> > you'll need of_device_is_compatible() here.
> 
> I see no reason to allocate a compatible property to the bank
> descriptors.  They're not being registered/actioned through
> of_platform_populate(), so ...

Well, this is all dependent on my comments on your DT binding patches. I
commented there that you did, at times, list a "compatible" property,
but you never actually used it and/or it was put in the wrong place. If
you determine that you do not need the property, then this comment is
also not applicable.

One reason for a "compatible" property might be if you have different
types of subnodes eventually, and you'll need to differentiate them. I
only see a need for a single type of subnode right now (the "bank"), but
it's possible you'd need to plan for the future.

> > [1] http://lists.infradead.org/pipermail/linux-mtd/2014-July/054500.html
> > [2] http://lists.infradead.org/pipermail/linux-mtd/2014-July/054881.html

Brian
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On Wed, 15 Oct 2014, Brian Norris wrote:

> On Thu, Oct 09, 2014 at 03:39:23PM +0100, Lee Jones wrote:
> > > > +static int check_erased_page(uint8_t *data, uint32_t page_size, int max_zeros)
> > > > +{
> > > > +	uint8_t *b = data;
> > > > +	int zeros = 0;
> > > > +	int i;
> > > > +
> > > > +	for (i = 0; i < page_size; i++) {
> > > > +		zeros += hweight8(~*b++);
> > > > +		if (zeros > max_zeros)
> > > > +			return -1;
> > > > +	}
> > > > +
> > > > +	if (zeros)
> > > > +		memset(data, 0xff, page_size);
> > > > +
> > > > +	return zeros;
> > > > +}
> > > 
> > > I pointed out some flaws in this function back in July [1]. You said
> > > you'd look into this one [2]. I really don't want to accept yet another
> > > custom, unsound erased-page check if at all possible.
> > 
> > That's not quite true.  I said that I think it doesn't matter about
> > not taking the OOB area into consideration, which I still believe is
> > the case.  This controller does not allow access into the OOB area.
> 
> Perhaps I'm not being clear enough.
> 
> While the controller may not allow you to program the spare area
> directly, you do so implicitly by allowing the controller to program BCH
> parity bytes to the spare area, right? So when you want to check if the
> page is blank, you have to consider ALL areas that will be used -- both
> in-band and out-of-band.
> 
> So, I'll repeat my question and try to elaborate:
> 
>   "What if this is a mostly-blank page, with ECC data, but most of the
>   bitflips are in the spare area? Then you will "correct" this page to
>   all 0xFF, not noticing that this was really not a blank page at all."
> 
> More specifically:
> 
>   1. Suppose you program a page with just a single byte of non-0xff
>   data, and your correction strength is at least 8 bits per sector
> 
>   2. When programming this page, your BCH controller writes parity bytes
>   to the spare area
> 
>   3. Over time (a lot of reads, for example), suppose you develop a lot
>   of bit flips in the spare area, such that your controller cannot
>   correct them any longer
> 
> Now consider two algorithms:
> 
>   (A) Your current proposal, to just check the in-band data that you can
>   easily access. If there are more than X zero-bits in the page, return
>   an error. Otherwise, clear the page and log a correctable error.
> 
>   (B) My suggestion, to check both the in-band and out-of-band. Same as
>   algorithm (A), except you check for X total zero-bits in both the
>   in-band and out-of-band
> 
> In the scenario I described, algorithm A will only notice up to 8 zero
> bits (in that single byte we programmed), so if X is greater than 8,
> algorithm A will falsely declare this an erased page and silently
> clobber the data we programmed to it.
> 
> Algorithm B would notice that there are many zero bits in the spare area
> (due to the programmed parity bytes) and will correctly declare this a
> corrupt, non-erased page.
> 
> If I've made any false assumptions in here, please point them out. But
> otherwise, I'd say that any erased-page detection algorithm that ignores
> the spare area is incorrect.
> 
> If you agree with me, then you have at least two options:
> 
> (1) Remove this erased page check entirely from the initial driver, with
>     a TODO item to add spare area read support and to improve this
>     algorithm
> 
> (2) Keep the check as-is, but put a large FIXME warning which notes why
>     the algorithm is wrong. It's possible the wrong algorithm is still
>     marginally better than no erased-page detection at all. I'm not sure
>     what the probability distributions are like for this sort of error.

Thanks for taking the time to explain your points so thoughly, I
appreciate that a great deal.  After chatting with Angus it transpires
that check_erased_page() does not check the OOB intentionally. This
behaviour is documented (in a Documentation/ file that I didn't know
exsited).  I will take the liberty of placing an extract of this
document and placing it in the driver as a comment.

FYI:

  "The most robust approach would be to use Hamming-FLEX to re-read the entire
  raw page+OOB data.  However, it is assumed that just checking the returned
  'raw' page data offers an acceptable compromise with minimal impact on
  performance.  (Is is possible to get a genuine uncorrectable ECC error where
  the page data is all 0xff?)"

> > > > +/* Returns the number of ECC errors, or '-1' for uncorrectable error */
> > > > +int bch_read_page(struct nandi_controller *nandi,
> > > > +		  loff_t offs,
> > > > +		  uint8_t *buf)
> > > > +{
> > > > +	struct nand_chip *chip = &nandi->info.chip;
> > > > +	struct bch_prog *prog = &bch_prog_read_page;
> > > > +	uint32_t page_size = nandi->info.mtd.writesize;
> > > > +	unsigned long list_phys;
> > > 
> > > Please use dma_addr_t. This is an intentionally opaque (to some degree)
> > > type.
> > > 
> > > > +	unsigned long buf_phys;
> > > 
> > > Ditto.
> > > 
> > > BTW, is your hardware actually restricted to a 32-bit address space? If
> > > it has some expanded registers for larger physical address ranges, it'd
> > > be good to handle the upper bits of the DMA address when mapping. Or
> > > else, it would be good to reflect this in your driver with
> > > dma_set_mask() I think.
> > 
> > Yes, it's 32bit only.  I will add a call to dma_set_mask() to reflect
> > this.
> > 
> > ... or not.  See below.

Added.

> > > > +	uint32_t ecc_err;
> > > > +	int ret = 0;
> > > > +
> > > > +	dev_dbg(nandi->dev, "%s: offs = 0x%012llx\n", __func__, offs);
> > > > +
> > > > +	BUG_ON(offs & (NANDI_BCH_DMA_ALIGNMENT - 1));
> > > > +
> > > > +	emiss_nandi_select(nandi, STM_NANDI_BCH);
> > > > +
> > > > +	nandi_enable_interrupts(nandi, NANDBCH_INT_SEQNODESOVER);
> > > > +	reinit_completion(&nandi->seq_completed);
> > > > +
> > > > +	/* Reset ECC stats */
> > > > +	writel(CFG_RESET_ECC_ALL | CFG_ENABLE_AFM,
> > > > +	       nandi->base + NANDBCH_CONTROLLER_CFG);
> > > > +	writel(CFG_ENABLE_AFM, nandi->base + NANDBCH_CONTROLLER_CFG);
> > > > +
> > > > +	prog->addr = (uint32_t)((offs >> (chip->page_shift - 8)) & 0xffffff00);
> > > > +
> > > > +	buf_phys = dma_map_single(NULL, buf, page_size, DMA_FROM_DEVICE);
> > > 
> > > Why NULL for the first arg? You should use the proper device (which will
> > > help with the 32-bit / 64-bit masking, I think.
> > > 
> > > Also, dma_map_single() can fail. It's good practice to check the return
> > > value with dma_mapping_error(). Same in a few other places.
> > 
> > If you do not supply the first parameter here, it falls back to
> > arm_dma_ops, which is what we want.  I guess this is also why we do
> > not have to set the DMA mask, as we're running on ARM32, rather than
> > AARCH64.
> 
> I think it's standard practice to make your hardware limitations
> explicit when writing a driver. From Documentation/DMA-API-HOWTO.txt
> under "DMA addressing limitations":
> 
>   "It is good style to do this even if your device holds the default
>   setting, because this shows that you did think about these issues wrt.
>   your device."
> 
> But I won't press this issue.

As above.  Although, I think the first parameter of dma_map_single()
needs to stay NULL for the desired behaviour.

> > > > +static int bch_mtd_read_oob(struct mtd_info *mtd,
> > > > +			    struct nand_chip *chip, int page)
> > > > +{
> > > > +	BUG();
> > > 
> > > Are you sure this can't be implemented, even if it's not the expected
> > > mode of operation? That's really unforunate.
> > 
> > It can.  We have a 'special' function for it using the extended
> > flexible mode.  Trying to upstream this has been hard enough already,
> > without more crud to deal with.  I will hopefully be adding this
> > functionality as small, succinct patches subsequently.
> 
> OK. But this is relevant to my points above -- particularly, you might
> want the 'read OOB' functionality to properly implement the erased page
> check.

I have added it anyway, as it's required by our BBT code.

> > > > +	for_each_child_of_node(np, banknp) {
> > > 
> > > If you change the DT binding to require a proper compatible property,
> > > you'll need of_device_is_compatible() here.
> > 
> > I see no reason to allocate a compatible property to the bank
> > descriptors.  They're not being registered/actioned through
> > of_platform_populate(), so ...
> 
> Well, this is all dependent on my comments on your DT binding patches. I
> commented there that you did, at times, list a "compatible" property,
> but you never actually used it and/or it was put in the wrong place. If
> you determine that you do not need the property, then this comment is
> also not applicable.
> 
> One reason for a "compatible" property might be if you have different
> types of subnodes eventually, and you'll need to differentiate them. I
> only see a need for a single type of subnode right now (the "bank"), but
> it's possible you'd need to plan for the future.

Right, if that's the case I'll add them then.