[v8,2/2] clk: wpcm450: Add Nuvoton WPCM450 clock/reset controller driver

This driver implements the following features w.r.t. the clock and reset
controller in the WPCM450 SoC:

- It calculates the rates for all clocks managed by the clock controller
- It leaves the clock tree mostly unchanged, except that it enables/
  disables clock gates based on usage.
- It exposes the reset lines managed by the controller using the
  Generic Reset Controller subsystem

NOTE: If the driver and the corresponding devicetree node are present,
      the driver will disable "unused" clocks. This is problem until
      the clock relations are properly declared in the devicetree (in a
      later patch). Until then, the clk_ignore_unused kernel parameter
      can be used as a workaround.

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-by: Joel Stanley <joel@jms.id.au>
---
v8:
- Use %pe format specifier throughout the driver, as suggested by Philipp Zabel
- Add Joel's R-b

v7:
- https://lore.kernel.org/lkml/20230422220240.322572-3-j.neuschaefer@gmx.net/
- Simplify error handling by not deallocating resources

v6:
- Enable RESET_SIMPLE based on ARCH_WPCM450, not ARCH_NPCM, as suggested by Tomer Maimon

v5:
- https://lore.kernel.org/lkml/20221104161850.2889894-6-j.neuschaefer@gmx.net/
- Switch to using clk_parent_data

v4:
- Fix reset controller initialization

v3:
- Change reference clock name from "refclk" to "ref"
- Remove unused variable in return path of wpcm450_clk_register_pll
- Remove unused divisor tables

v2:
- no changes
---
 drivers/clk/Makefile      |   1 +
 drivers/clk/clk-wpcm450.c | 374 ++++++++++++++++++++++++++++++++++++++
 drivers/reset/Kconfig     |   2 +-
 3 files changed, 376 insertions(+), 1 deletion(-)
 create mode 100644 drivers/clk/clk-wpcm450.c

--
2.39.2

Quoting Jonathan Neuschäfer (2023-04-28 12:02:26)
> diff --git a/drivers/clk/clk-wpcm450.c b/drivers/clk/clk-wpcm450.c
> new file mode 100644
> index 0000000000000..358be5befa887
> --- /dev/null
> +++ b/drivers/clk/clk-wpcm450.c
> @@ -0,0 +1,374 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Nuvoton WPCM450 clock and reset controller driver.
> + *
> + * Copyright (C) 2022 Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/bitfield.h>
> +#include <linux/clk-provider.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/reset-controller.h>
> +#include <linux/reset/reset-simple.h>
> +#include <linux/slab.h>
> +
> +#include <dt-bindings/clock/nuvoton,wpcm450-clk.h>
> +
> +struct wpcm450_clk_pll {
> +       struct clk_hw hw;
> +       void __iomem *pllcon;
> +       u8 flags;
> +};
> +
> +#define to_wpcm450_clk_pll(_hw) container_of(_hw, struct wpcm450_clk_pll, hw)
> +
> +#define PLLCON_FBDV    GENMASK(24, 16)
> +#define PLLCON_PRST    BIT(13)
> +#define PLLCON_PWDEN   BIT(12)
> +#define PLLCON_OTDV    GENMASK(10, 8)
> +#define PLLCON_INDV    GENMASK(5, 0)
> +
> +static unsigned long wpcm450_clk_pll_recalc_rate(struct clk_hw *hw,
> +                                                unsigned long parent_rate)
> +{
> +       struct wpcm450_clk_pll *pll = to_wpcm450_clk_pll(hw);
> +       unsigned long fbdv, indv, otdv;
> +       u64 rate;
> +       u32 pllcon;
> +
> +       if (parent_rate == 0) {
> +               pr_err("%s: parent rate is zero", __func__);

This can happen more often than you think, so probably best to remove
it.

> +               return 0;
> +       }
> +
> +       pllcon = readl_relaxed(pll->pllcon);
> +
> +       indv = FIELD_GET(PLLCON_INDV, pllcon) + 1;
> +       fbdv = FIELD_GET(PLLCON_FBDV, pllcon) + 1;
> +       otdv = FIELD_GET(PLLCON_OTDV, pllcon) + 1;
> +
> +       rate = (u64)parent_rate * fbdv;
> +       do_div(rate, indv * otdv);
> +
> +       return rate;
> +}
> +
> +static int wpcm450_clk_pll_is_enabled(struct clk_hw *hw)
> +{
> +       struct wpcm450_clk_pll *pll = to_wpcm450_clk_pll(hw);
> +       u32 pllcon;
> +
> +       pllcon = readl_relaxed(pll->pllcon);
> +
> +       return !(pllcon & PLLCON_PRST);
> +}
> +
> +static void wpcm450_clk_pll_disable(struct clk_hw *hw)
> +{
> +       struct wpcm450_clk_pll *pll = to_wpcm450_clk_pll(hw);
> +       u32 pllcon;
> +
> +       pllcon = readl_relaxed(pll->pllcon);
> +       pllcon |= PLLCON_PRST | PLLCON_PWDEN;
> +       writel(pllcon, pll->pllcon);
> +}
> +
> +static const struct clk_ops wpcm450_clk_pll_ops = {
> +       .recalc_rate = wpcm450_clk_pll_recalc_rate,
> +       .is_enabled = wpcm450_clk_pll_is_enabled,
> +       .disable = wpcm450_clk_pll_disable
> +};
> +
> +static struct clk_hw *
> +wpcm450_clk_register_pll(void __iomem *pllcon, const char *name,
> +                        const struct clk_parent_data *parent, unsigned long flags)
> +{
> +       struct wpcm450_clk_pll *pll;
> +       struct clk_init_data init = {};
> +       int ret;
> +
> +       pll = kzalloc(sizeof(*pll), GFP_KERNEL);
> +       if (!pll)
> +               return ERR_PTR(-ENOMEM);
> +
> +       init.name = name;
> +       init.ops = &wpcm450_clk_pll_ops;
> +       init.parent_data = parent;
> +       init.num_parents = 1;
> +       init.flags = flags;
> +
> +       pll->pllcon = pllcon;
> +       pll->hw.init = &init;
> +
> +       ret = clk_hw_register(NULL, &pll->hw);
> +       if (ret) {
> +               kfree(pll);
> +               return ERR_PTR(ret);
> +       }
> +
> +       return &pll->hw;
> +}
> +
> +#define REG_CLKEN      0x00
> +#define REG_CLKSEL     0x04
> +#define REG_CLKDIV     0x08
> +#define REG_PLLCON0    0x0c
> +#define REG_PLLCON1    0x10
> +#define REG_PMCON      0x14
> +#define REG_IRQWAKECON 0x18
> +#define REG_IRQWAKEFLAG        0x1c
> +#define REG_IPSRST     0x20
> +
> +struct wpcm450_pll_data {
> +       const char *name;
> +       struct clk_parent_data parent;
> +       unsigned int reg;
> +       unsigned long flags;
> +};
> +
> +static const struct wpcm450_pll_data pll_data[] = {
> +       { "pll0", { .name = "ref" }, REG_PLLCON0, 0 },

This is new code, please don't use .name. Instead use .fw_name or .index with preference to
.index first and .hw if the pointer is available in this driver.

> +       { "pll1", { .name = "ref" }, REG_PLLCON1, 0 },
> +};
> +
> +struct wpcm450_clksel_data {
> +       const char *name;
> +       const struct clk_parent_data *parents;
> +       unsigned int num_parents;
> +       const u32 *table;
> +       int shift;
> +       int width;
> +       int index;
> +       unsigned long flags;
> +};
> +
> +static const u32 parent_table[] = { 0, 1, 2 };
> +
> +static const struct clk_parent_data default_parents[] = {
> +       { .name = "pll0" },
> +       { .name = "pll1" },
> +       { .name = "ref" },
> +};
> +
> +static const struct clk_parent_data huart_parents[] = {
> +       { .name = "ref" },
> +       { .name = "refdiv2" },
> +};
> +
> +static const struct wpcm450_clksel_data clksel_data[] = {
> +       { "cpusel", default_parents, ARRAY_SIZE(default_parents),
> +               parent_table, 0, 2, -1, CLK_IS_CRITICAL },
> +       { "clkout", default_parents, ARRAY_SIZE(default_parents),
> +               parent_table, 2, 2, -1, 0 },
> +       { "usbphy", default_parents, ARRAY_SIZE(default_parents),
> +               parent_table, 6, 2, -1, 0 },
> +       { "uartsel", default_parents, ARRAY_SIZE(default_parents),
> +               parent_table, 8, 2, WPCM450_CLK_USBPHY, 0 },
> +       { "huartsel", huart_parents, ARRAY_SIZE(huart_parents),
> +               parent_table, 10, 1, -1, 0 },
> +};
> +
> +static const struct clk_div_table div_fixed2[] = {
> +       { .val = 0, .div = 2 },
> +       { }
> +};
> +
> +struct wpcm450_clkdiv_data {
> +       const char *name;
> +       struct clk_parent_data parent;
> +       int div_flags;
> +       const struct clk_div_table *table;
> +       int shift;
> +       int width;
> +       unsigned long flags;
> +};
> +
> +static struct wpcm450_clkdiv_data clkdiv_data_early[] = {
> +       { "refdiv2", { .name = "ref" }, 0, div_fixed2, 0, 0 },
> +};
> +
> +static const struct wpcm450_clkdiv_data clkdiv_data[] = {
> +       { "cpu", { .name = "cpusel" }, 0, div_fixed2, 0, 0, CLK_IS_CRITICAL },
> +       { "adcdiv", { .name = "ref" }, CLK_DIVIDER_POWER_OF_TWO, NULL, 28, 2, 0 },
> +       { "apb", { .name = "ahb" }, CLK_DIVIDER_POWER_OF_TWO, NULL, 26, 2, 0 },
> +       { "ahb", { .name = "cpu" }, CLK_DIVIDER_POWER_OF_TWO, NULL, 24, 2, 0 },
> +       { "uart", { .name = "uartsel" }, 0, NULL, 16, 4, 0 },
> +       { "ahb3", { .name = "ahb" }, CLK_DIVIDER_POWER_OF_TWO, NULL, 8, 2, 0 },
> +};
> +
> +struct wpcm450_clken_data {
> +       const char *name;
> +       struct clk_parent_data parent;
> +       int bitnum;
> +       unsigned long flags;
> +};
> +
> +static const struct wpcm450_clken_data clken_data[] = {
> +       { "fiu", { .name = "ahb3" }, WPCM450_CLK_FIU, 0 },
> +       { "xbus", { .name = "ahb3" }, WPCM450_CLK_XBUS, 0 },
> +       { "kcs", { .name = "apb" }, WPCM450_CLK_KCS, 0 },
> +       { "shm", { .name = "ahb3" }, WPCM450_CLK_SHM, 0 },
> +       { "usb1", { .name = "ahb" }, WPCM450_CLK_USB1, 0 },
> +       { "emc0", { .name = "ahb" }, WPCM450_CLK_EMC0, 0 },
> +       { "emc1", { .name = "ahb" }, WPCM450_CLK_EMC1, 0 },
> +       { "usb0", { .name = "ahb" }, WPCM450_CLK_USB0, 0 },
> +       { "peci", { .name = "apb" }, WPCM450_CLK_PECI, 0 },
> +       { "aes", { .name = "apb" }, WPCM450_CLK_AES, 0 },
> +       { "uart0", { .name = "uart" }, WPCM450_CLK_UART0, 0 },
> +       { "uart1", { .name = "uart" }, WPCM450_CLK_UART1, 0 },
> +       { "smb2", { .name = "apb" }, WPCM450_CLK_SMB2, 0 },
> +       { "smb3", { .name = "apb" }, WPCM450_CLK_SMB3, 0 },
> +       { "smb4", { .name = "apb" }, WPCM450_CLK_SMB4, 0 },
> +       { "smb5", { .name = "apb" }, WPCM450_CLK_SMB5, 0 },
> +       { "huart", { .name = "huartsel" }, WPCM450_CLK_HUART, 0 },
> +       { "pwm", { .name = "apb" }, WPCM450_CLK_PWM, 0 },
> +       { "timer0", { .name = "refdiv2" }, WPCM450_CLK_TIMER0, 0 },
> +       { "timer1", { .name = "refdiv2" }, WPCM450_CLK_TIMER1, 0 },
> +       { "timer2", { .name = "refdiv2" }, WPCM450_CLK_TIMER2, 0 },
> +       { "timer3", { .name = "refdiv2" }, WPCM450_CLK_TIMER3, 0 },
> +       { "timer4", { .name = "refdiv2" }, WPCM450_CLK_TIMER4, 0 },
> +       { "mft0", { .name = "apb" }, WPCM450_CLK_MFT0, 0 },
> +       { "mft1", { .name = "apb" }, WPCM450_CLK_MFT1, 0 },
> +       { "wdt", { .name = "refdiv2" }, WPCM450_CLK_WDT, 0 },
> +       { "adc", { .name = "adcdiv" }, WPCM450_CLK_ADC, 0 },
> +       { "sdio", { .name = "ahb" }, WPCM450_CLK_SDIO, 0 },
> +       { "sspi", { .name = "apb" }, WPCM450_CLK_SSPI, 0 },
> +       { "smb0", { .name = "apb" }, WPCM450_CLK_SMB0, 0 },
> +       { "smb1", { .name = "apb" }, WPCM450_CLK_SMB1, 0 },
> +};
> +
> +static DEFINE_SPINLOCK(wpcm450_clk_lock);
> +
> +/*
> + * NOTE: Error handling is very rudimentary here. If the clock driver initial-
> + * ization fails, the system is probably in bigger trouble than what is caused
> + * by a few leaked resources.
> + */
> +
> +static void __init wpcm450_clk_init(struct device_node *clk_np)
> +{
> +       struct clk_hw_onecell_data *clk_data;
> +       static struct clk_hw **hws;
> +       static struct clk_hw *hw;
> +       void __iomem *clk_base;
> +       int i, ret;
> +       struct reset_simple_data *reset;
> +
> +       clk_base = of_iomap(clk_np, 0);
> +       if (!clk_base) {
> +               pr_err("%pOFP: failed to map registers\n", clk_np);
> +               of_node_put(clk_np);
> +               return;
> +       }
> +       of_node_put(clk_np);
> +
> +       clk_data = kzalloc(struct_size(clk_data, hws, WPCM450_NUM_CLKS), GFP_KERNEL);
> +       if (!clk_data)
> +               return;
> +
> +       clk_data->num = WPCM450_NUM_CLKS;
> +       hws = clk_data->hws;
> +
> +       for (i = 0; i < WPCM450_NUM_CLKS; i++)
> +               hws[i] = ERR_PTR(-ENOENT);
> +
> +       // PLLs

Please use /* comments like this */

> +       for (i = 0; i < ARRAY_SIZE(pll_data); i++) {
> +               const struct wpcm450_pll_data *data = &pll_data[i];
> +
> +               hw = wpcm450_clk_register_pll(clk_base + data->reg, data->name,
> +                                             &data->parent, data->flags);
> +               if (IS_ERR(hw)) {
> +                       pr_info("Failed to register PLL: %pe", hw);

Missing newline?

> +                       return;
> +               }
> +       }
> +
> +       // Early divisors (REF/2)
> +       for (i = 0; i < ARRAY_SIZE(clkdiv_data_early); i++) {
> +               const struct wpcm450_clkdiv_data *data = &clkdiv_data_early[i];
> +
> +               hw = clk_hw_register_divider_table_parent_data(NULL, data->name, &data->parent,
> +                                                              data->flags, clk_base + REG_CLKDIV,
> +                                                              data->shift, data->width,
> +                                                              data->div_flags, data->table,
> +                                                              &wpcm450_clk_lock);
> +               if (IS_ERR(hw)) {
> +                       pr_err("Failed to register div table: %pe\n", hw);
> +                       return;
> +               }
> +       }
> +
> +       // Selects/muxes
> +       for (i = 0; i < ARRAY_SIZE(clksel_data); i++) {
> +               const struct wpcm450_clksel_data *data = &clksel_data[i];
> +
> +               hw = clk_hw_register_mux_parent_data(NULL, data->name, data->parents,
> +                                                    data->num_parents, data->flags,
> +                                                    clk_base + REG_CLKSEL, data->shift,
> +                                                    data->width, 0,
> +                                                    &wpcm450_clk_lock);
> +               if (IS_ERR(hw)) {
> +                       pr_err("Failed to register mux: %pe\n", hw);
> +                       return;
> +               }
> +               if (data->index >= 0)
> +                       clk_data->hws[data->index] = hw;
> +       }
> +
> +       // Divisors
> +       for (i = 0; i < ARRAY_SIZE(clkdiv_data); i++) {
> +               const struct wpcm450_clkdiv_data *data = &clkdiv_data[i];
> +
> +               hw = clk_hw_register_divider_table_parent_data(NULL, data->name, &data->parent,
> +                                                              data->flags, clk_base + REG_CLKDIV,
> +                                                              data->shift, data->width,
> +                                                              data->div_flags, data->table,
> +                                                              &wpcm450_clk_lock);
> +               if (IS_ERR(hw)) {
> +                       pr_err("Failed to register divider: %pe\n", hw);
> +                       return;
> +               }
> +       }
> +
> +       // Enables/gates
> +       for (i = 0; i < ARRAY_SIZE(clken_data); i++) {
> +               const struct wpcm450_clken_data *data = &clken_data[i];
> +
> +               hw = clk_hw_register_gate_parent_data(NULL, data->name, &data->parent, data->flags,
> +                                                     clk_base + REG_CLKEN, data->bitnum,
> +                                                     data->flags, &wpcm450_clk_lock);
> +               if (IS_ERR(hw)) {
> +                       pr_err("Failed to register gate: %pe\n", hw);
> +                       return;
> +               }
> +               clk_data->hws[data->bitnum] = hw;
> +       }
> +
> +       ret = of_clk_add_hw_provider(clk_np, of_clk_hw_onecell_get, clk_data);
> +       if (ret)
> +               pr_err("Failed to add DT provider: %pe\n", ERR_PTR(ret));
> +
> +       // Reset controller
> +       reset = kzalloc(sizeof(*reset), GFP_KERNEL);
> +       if (!reset)
> +               return;
> +       reset->rcdev.owner = THIS_MODULE;
> +       reset->rcdev.nr_resets = WPCM450_NUM_RESETS;
> +       reset->rcdev.ops = &reset_simple_ops;
> +       reset->rcdev.of_node = clk_np;
> +       reset->membase = clk_base + REG_IPSRST;
> +       ret = reset_controller_register(&reset->rcdev);
> +       if (ret)
> +               pr_err("Failed to register reset controller: %pe\n", ERR_PTR(ret));
> +
> +       of_node_put(clk_np);
> +}
> +
> +CLK_OF_DECLARE(wpcm450_clk_init, "nuvoton,wpcm450-clk", wpcm450_clk_init);

Is something preventing this from being a platform driver?

On Thu, Jul 20, 2023 at 05:02:15PM -0700, Stephen Boyd wrote:
> Quoting Jonathan Neuschäfer (2023-04-28 12:02:26)
> > diff --git a/drivers/clk/clk-wpcm450.c b/drivers/clk/clk-wpcm450.c
[...]
> > +static unsigned long wpcm450_clk_pll_recalc_rate(struct clk_hw *hw,
> > +                                                unsigned long parent_rate)
> > +{
> > +       struct wpcm450_clk_pll *pll = to_wpcm450_clk_pll(hw);
> > +       unsigned long fbdv, indv, otdv;
> > +       u64 rate;
> > +       u32 pllcon;
> > +
> > +       if (parent_rate == 0) {
> > +               pr_err("%s: parent rate is zero", __func__);
> 
> This can happen more often than you think, so probably best to remove
> it.

Alright.

> > +static const struct wpcm450_pll_data pll_data[] = {
> > +       { "pll0", { .name = "ref" }, REG_PLLCON0, 0 },
> 
> This is new code, please don't use .name. Instead use .fw_name or .index with preference to
> .index first and .hw if the pointer is available in this driver.

As far as I can see, .fw_name and .index depend on a struct device*
being passed to clk_hw_register, which won't be available unless I
actually convert the driver to a platform driver.

Not relying on .name would indeed be nice.

> > +       // PLLs
> 
> Please use /* comments like this */

Ok.

> 
> > +       for (i = 0; i < ARRAY_SIZE(pll_data); i++) {
> > +               const struct wpcm450_pll_data *data = &pll_data[i];
> > +
> > +               hw = wpcm450_clk_register_pll(clk_base + data->reg, data->name,
> > +                                             &data->parent, data->flags);
> > +               if (IS_ERR(hw)) {
> > +                       pr_info("Failed to register PLL: %pe", hw);
> 
> Missing newline?

Indeed.

> > +CLK_OF_DECLARE(wpcm450_clk_init, "nuvoton,wpcm450-clk", wpcm450_clk_init);
> 
> Is something preventing this from being a platform driver?

As far as I remember I have tried to convert it to a platform driver but
wasn't very successful/satisfied. Unfortunately I didn't take detailed notes.

I'll give it another try.


Best regards,
Jonathan