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From: Linus Walleij <linus.walleij@linaro.org>
To: Thierry Reding <thierry.reding@gmail.com>, dri-devel@lists.freedesktop.org
Subject: [PATCH 2/2 v4] drm/panel: Add a driver for the TPO TPG110
Date: Thu,  1 Nov 2018 22:32:56 +0100
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The TPO (Toppoly) TPG110 is a pretty generic display driver
similar in vein to the Ilitek 93xx devices. It is not a panel
per se but a driver used with several low-cost noname panels.

This is used on the Nomadik NHK15 combined with a OSD
OSD057VA01CT display for WVGA 800x480.

The driver is pretty minimalistic right now but can be
extended to handle non-default polarities, gamma correction
etc.

The driver is based on the baked-in code in
drivers/video/fbdev/amba-clcd-nomadik.c which will be
decomissioned once this us upstream.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v3->v4:
- Tag on the SPI_3WIRE_HIZ flag to the SPI slave mode.
ChangeLog v2->v3:
- Rewrite as an SPI child device.
---
 MAINTAINERS                              |   7 +
 drivers/gpu/drm/panel/Kconfig            |  10 +
 drivers/gpu/drm/panel/Makefile           |   1 +
 drivers/gpu/drm/panel/panel-tpo-tpg110.c | 506 +++++++++++++++++++++++
 4 files changed, 524 insertions(+)
 create mode 100644 drivers/gpu/drm/panel/panel-tpo-tpg110.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 690c2f68a401..c3ca56c2a7a6 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4746,6 +4746,13 @@ DRM DRIVER FOR TDFX VIDEO CARDS
 S:	Orphan / Obsolete
 F:	drivers/gpu/drm/tdfx/
 
+DRM DRIVER FOR TPO TPG110 PANELS
+M:	Linus Walleij <linus.walleij@linaro.org>
+T:	git git://anongit.freedesktop.org/drm/drm-misc
+S:	Maintained
+F:	drivers/gpu/drm/panel/panel-tpo-tpg110.c
+F:	Documentation/devicetree/bindings/display/panel/tpo,tpg110.txt
+
 DRM DRIVER FOR USB DISPLAYLINK VIDEO ADAPTERS
 M:	Dave Airlie <airlied@redhat.com>
 R:	Sean Paul <sean@poorly.run>
diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index 6020c30a33b3..b2c8b02894b1 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -186,4 +186,14 @@ config DRM_PANEL_SITRONIX_ST7789V
 	  Say Y here if you want to enable support for the Sitronix
 	  ST7789V controller for 240x320 LCD panels
 
+config DRM_PANEL_TPO_TPG110
+	tristate "TPO TPG 800x400 panel"
+	depends on OF && SPI && GPIOLIB
+	depends on BACKLIGHT_CLASS_DEVICE
+	select VIDEOMODE_HELPERS
+	help
+	  Say Y here if you want to enable support for TPO TPG110
+	  400CH LTPS TFT LCD Single Chip Digital Driver for up to
+	  800x400 LCD panels.
+
 endmenu
diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
index 5ccaaa9d13af..9b3a0629d255 100644
--- a/drivers/gpu/drm/panel/Makefile
+++ b/drivers/gpu/drm/panel/Makefile
@@ -19,3 +19,4 @@ obj-$(CONFIG_DRM_PANEL_SEIKO_43WVF1G) += panel-seiko-43wvf1g.o
 obj-$(CONFIG_DRM_PANEL_SHARP_LQ101R1SX01) += panel-sharp-lq101r1sx01.o
 obj-$(CONFIG_DRM_PANEL_SHARP_LS043T1LE01) += panel-sharp-ls043t1le01.o
 obj-$(CONFIG_DRM_PANEL_SITRONIX_ST7789V) += panel-sitronix-st7789v.o
+obj-$(CONFIG_DRM_PANEL_TPO_TPG110) += panel-tpo-tpg110.o
diff --git a/drivers/gpu/drm/panel/panel-tpo-tpg110.c b/drivers/gpu/drm/panel/panel-tpo-tpg110.c
new file mode 100644
index 000000000000..8e517ea5e73b
--- /dev/null
+++ b/drivers/gpu/drm/panel/panel-tpo-tpg110.c
@@ -0,0 +1,506 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Panel driver for the TPO TPG110 400CH LTPS TFT LCD Single Chip
+ * Digital Driver.
+ *
+ * This chip drives a TFT LCD, so it does not know what kind of
+ * display is actually connected to it, so the width and height of that
+ * display needs to be supplied from the machine configuration.
+ *
+ * Author:
+ * Linus Walleij <linus.wallei@linaro.org>
+ */
+#include <drm/drmP.h>
+#include <drm/drm_panel.h>
+
+#include <linux/backlight.h>
+#include <linux/bitops.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/spi/spi.h>
+
+#include <video/of_videomode.h>
+#include <video/videomode.h>
+
+#define TPG110_TEST			0x00
+#define TPG110_CHIPID			0x01
+#define TPG110_CTRL1			0x02
+#define TPG110_RES_MASK			GENMASK(2, 0)
+#define TPG110_RES_800X480		0x07
+#define TPG110_RES_640X480		0x06
+#define TPG110_RES_480X272		0x05
+#define TPG110_RES_480X640		0x04
+#define TPG110_RES_480X272_D		0x01 /* Dual scan: outputs 800x480 */
+#define TPG110_RES_400X240_D		0x00 /* Dual scan: outputs 800x480 */
+#define TPG110_CTRL2			0x03
+#define TPG110_CTRL2_PM			BIT(0)
+#define TPG110_CTRL2_RES_PM_CTRL	BIT(7)
+
+/**
+ * struct tpg110_panel_mode - lookup struct for the supported modes
+ */
+struct tpg110_panel_mode {
+	/**
+	 * @name: the name of this panel
+	 */
+	const char *name;
+	/**
+	 * @magic: the magic value from the detection register
+	 */
+	u32 magic;
+	/**
+	 * @mode: the DRM display mode for this panel
+	 */
+	struct drm_display_mode mode;
+	/**
+	 * @bus_flags: the DRM bus flags for this panel e.g. inverted clock
+	 */
+	u32 bus_flags;
+};
+
+/**
+ * struct tpg110 - state container for the TPG110 panel
+ */
+struct tpg110 {
+	/**
+	 * @dev: the container device
+	 */
+	struct device *dev;
+	/**
+	 * @spi: the corresponding SPI device
+	 */
+	struct spi_device *spi;
+	/**
+	 * @panel: the DRM panel instance for this device
+	 */
+	struct drm_panel panel;
+	/**
+	 * @backlight: backlight for this panel
+	 */
+	struct backlight_device *backlight;
+	/**
+	 * @panel_type: the panel mode as detected
+	 */
+	const struct tpg110_panel_mode *panel_mode;
+	/**
+	 * @width: the width of this panel in mm
+	 */
+	u32 width;
+	/**
+	 * @height: the height of this panel in mm
+	 */
+	u32 height;
+	/**
+	 * @grestb: reset GPIO line
+	 */
+	struct gpio_desc *grestb;
+};
+
+/*
+ * TPG110 modes, these are the simple modes, the dualscan modes that
+ * take 400x240 or 480x272 in and display as 800x480 are not listed.
+ */
+static const struct tpg110_panel_mode tpg110_modes[] = {
+	{
+		.name = "800x480 RGB",
+		.magic = TPG110_RES_800X480,
+		.mode = {
+			.clock = 33200,
+			.hdisplay = 800,
+			.hsync_start = 800 + 40,
+			.hsync_end = 800 + 40 + 1,
+			.htotal = 800 + 40 + 1 + 216,
+			.vdisplay = 480,
+			.vsync_start = 480 + 10,
+			.vsync_end = 480 + 10 + 1,
+			.vtotal = 480 + 10 + 1 + 35,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "640x480 RGB",
+		.magic = TPG110_RES_640X480,
+		.mode = {
+			.clock = 25200,
+			.hdisplay = 640,
+			.hsync_start = 640 + 24,
+			.hsync_end = 640 + 24 + 1,
+			.htotal = 640 + 24 + 1 + 136,
+			.vdisplay = 480,
+			.vsync_start = 480 + 18,
+			.vsync_end = 480 + 18 + 1,
+			.vtotal = 480 + 18 + 1 + 27,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "480x272 RGB",
+		.magic = TPG110_RES_480X272,
+		.mode = {
+			.clock = 9000,
+			.hdisplay = 480,
+			.hsync_start = 480 + 2,
+			.hsync_end = 480 + 2 + 1,
+			.htotal = 480 + 2 + 1 + 43,
+			.vdisplay = 272,
+			.vsync_start = 272 + 2,
+			.vsync_end = 272 + 2 + 1,
+			.vtotal = 272 + 2 + 1 + 12,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "480x640 RGB",
+		.magic = TPG110_RES_480X640,
+		.mode = {
+			.clock = 20500,
+			.hdisplay = 480,
+			.hsync_start = 480 + 2,
+			.hsync_end = 480 + 2 + 1,
+			.htotal = 480 + 2 + 1 + 43,
+			.vdisplay = 640,
+			.vsync_start = 640 + 4,
+			.vsync_end = 640 + 4 + 1,
+			.vtotal = 640 + 4 + 1 + 8,
+			.vrefresh = 60,
+		},
+	},
+	{
+		.name = "400x240 RGB",
+		.magic = TPG110_RES_400X240_D,
+		.mode = {
+			.clock = 8300,
+			.hdisplay = 400,
+			.hsync_start = 400 + 20,
+			.hsync_end = 400 + 20 + 1,
+			.htotal = 400 + 20 + 1 + 108,
+			.vdisplay = 240,
+			.vsync_start = 240 + 2,
+			.vsync_end = 240 + 2 + 1,
+			.vtotal = 240 + 2 + 1 + 20,
+			.vrefresh = 60,
+		},
+	},
+};
+
+static inline struct tpg110 *
+to_tpg110(struct drm_panel *panel)
+{
+	return container_of(panel, struct tpg110, panel);
+}
+
+static u8 tpg110_readwrite_reg(struct tpg110 *tpg, bool write,
+			       u8 address, u8 outval)
+{
+	struct spi_message m;
+	struct spi_transfer t[2];
+	u8 buf[2];
+	int ret;
+
+	spi_message_init(&m);
+	memset(t, 0, sizeof(t));
+
+	if (write) {
+		/*
+		 * Clear address bit 0, 1 when writing, just to be sure
+		 * The actual bit indicating a write here is bit 1, bit
+		 * 0 is just surplus to pad it up to 8 bits.
+		 */
+		buf[0] = address << 2;
+		buf[0] &= ~0x03;
+		buf[1] = outval;
+
+		t[0].bits_per_word = 8;
+		t[0].tx_buf = &buf[0];
+		t[0].len = 1;
+
+		t[1].tx_buf = &buf[1];
+		t[1].len = 1;
+		t[1].bits_per_word = 8;
+	} else {
+		/* Set address bit 0 to 1 to read */
+		buf[0] = address << 1;
+		buf[0] |= 0x01;
+
+		/*
+		 * The last bit/clock is Hi-Z turnaround cycle, so we need
+		 * to send only 7 bits here. The 8th bit is the high impedance
+		 * turn-around cycle.
+		 */
+		t[0].bits_per_word = 7;
+		t[0].tx_buf = &buf[0];
+		t[0].len = 1;
+
+		t[1].rx_buf = &buf[1];
+		t[1].len = 1;
+		t[1].bits_per_word = 8;
+	}
+
+	spi_message_add_tail(&t[0], &m);
+	spi_message_add_tail(&t[1], &m);
+	ret = spi_sync(tpg->spi, &m);
+	if (ret) {
+		dev_err(tpg->dev, "SPI message error %d\n", ret);
+		return ret;
+	}
+	if (write)
+		return 0;
+	/* Read */
+	return buf[1];
+}
+
+static u8 tpg110_read_reg(struct tpg110 *tpg, u8 address)
+{
+	return tpg110_readwrite_reg(tpg, false, address, 0);
+}
+
+static void tpg110_write_reg(struct tpg110 *tpg, u8 address, u8 outval)
+{
+	tpg110_readwrite_reg(tpg, true, address, outval);
+}
+
+static int tpg110_startup(struct tpg110 *tpg)
+{
+	u8 val;
+	int i;
+
+	/* De-assert the reset signal */
+	gpiod_set_value_cansleep(tpg->grestb, 0);
+	mdelay(1);
+	dev_info(tpg->dev, "de-asserted GRESTB\n");
+
+	/* Test display communication */
+	tpg110_write_reg(tpg, TPG110_TEST, 0x55);
+	val = tpg110_read_reg(tpg, TPG110_TEST);
+	if (val != 0x55) {
+		dev_err(tpg->dev, "failed communication test\n");
+		return -ENODEV;
+	}
+
+	val = tpg110_read_reg(tpg, TPG110_CHIPID);
+	dev_info(tpg->dev, "TPG110 chip ID: %d version: %d\n",
+		 val >> 4, val & 0x0f);
+
+	/* Show display resolution */
+	val = tpg110_read_reg(tpg, TPG110_CTRL1);
+	val &= TPG110_RES_MASK;
+	switch (val) {
+	case TPG110_RES_400X240_D:
+		dev_info(tpg->dev,
+			 "IN 400x240 RGB -> OUT 800x480 RGB (dual scan)");
+		break;
+	case TPG110_RES_480X272_D:
+		dev_info(tpg->dev,
+			 "IN 480x272 RGB -> OUT 800x480 RGB (dual scan)");
+		break;
+	case TPG110_RES_480X640:
+		dev_info(tpg->dev, "480x640 RGB");
+		break;
+	case TPG110_RES_480X272:
+		dev_info(tpg->dev, "480x272 RGB");
+		break;
+	case TPG110_RES_640X480:
+		dev_info(tpg->dev, "640x480 RGB");
+		break;
+	case TPG110_RES_800X480:
+		dev_info(tpg->dev, "800x480 RGB");
+		break;
+	default:
+		dev_info(tpg->dev, "ILLEGAL RESOLUTION");
+		break;
+	}
+
+	/* From the producer side, this is the same resolution */
+	if (val == TPG110_RES_480X272_D)
+		val = TPG110_RES_480X272;
+
+	for (i = 0; i < ARRAY_SIZE(tpg110_modes); i++) {
+		const struct tpg110_panel_mode *pm;
+
+		pm = &tpg110_modes[i];
+		if (pm->magic == val) {
+			tpg->panel_mode = pm;
+			break;
+		}
+	}
+	if (i == ARRAY_SIZE(tpg110_modes)) {
+		dev_err(tpg->dev, "unsupported mode (%02x) detected\n",
+			val);
+		return -ENODEV;
+	}
+
+	val = tpg110_read_reg(tpg, TPG110_CTRL2);
+	dev_info(tpg->dev, "resolution and standby is controlled by %s\n",
+		 (val & TPG110_CTRL2_RES_PM_CTRL) ? "software" : "hardware");
+	/* Take control over resolution and standby */
+	val |= TPG110_CTRL2_RES_PM_CTRL;
+	tpg110_write_reg(tpg, TPG110_CTRL2, val);
+
+	return 0;
+}
+
+static int tpg110_disable(struct drm_panel *panel)
+{
+	struct tpg110 *tpg = to_tpg110(panel);
+	u8 val;
+
+	/* Put chip into standby */
+	val = tpg110_read_reg(tpg, TPG110_CTRL2_PM);
+	val &= ~TPG110_CTRL2_PM;
+	tpg110_write_reg(tpg, TPG110_CTRL2_PM, val);
+
+	if (tpg->backlight) {
+		tpg->backlight->props.power = FB_BLANK_POWERDOWN;
+		tpg->backlight->props.state |= BL_CORE_FBBLANK;
+		backlight_update_status(tpg->backlight);
+	}
+
+	return 0;
+}
+
+static int tpg110_enable(struct drm_panel *panel)
+{
+	struct tpg110 *tpg = to_tpg110(panel);
+	u8 val;
+
+	if (tpg->backlight) {
+		tpg->backlight->props.state &= ~BL_CORE_FBBLANK;
+		tpg->backlight->props.power = FB_BLANK_UNBLANK;
+		backlight_update_status(tpg->backlight);
+	}
+
+	/* Take chip out of standby */
+	val = tpg110_read_reg(tpg, TPG110_CTRL2_PM);
+	val |= TPG110_CTRL2_PM;
+	tpg110_write_reg(tpg, TPG110_CTRL2_PM, val);
+
+	return 0;
+}
+
+/**
+ * tpg110_get_modes() - return the appropriate mode
+ * @panel: the panel to get the mode for
+ *
+ * This currently does not present a forest of modes, instead it
+ * presents the mode that is configured for the system under use,
+ * and which is detected by reading the registers of the display.
+ */
+static int tpg110_get_modes(struct drm_panel *panel)
+{
+	struct drm_connector *connector = panel->connector;
+	struct tpg110 *tpg = to_tpg110(panel);
+	struct drm_display_mode *mode;
+
+	strncpy(connector->display_info.name, tpg->panel_mode->name,
+		DRM_DISPLAY_INFO_LEN);
+	connector->display_info.width_mm = tpg->width;
+	connector->display_info.height_mm = tpg->height;
+	connector->display_info.bus_flags = tpg->panel_mode->bus_flags;
+
+	mode = drm_mode_duplicate(panel->drm, &tpg->panel_mode->mode);
+	drm_mode_set_name(mode);
+	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+
+	mode->width_mm = tpg->width;
+	mode->height_mm = tpg->height;
+
+	drm_mode_probed_add(connector, mode);
+
+	return 1;
+}
+
+static const struct drm_panel_funcs tpg110_drm_funcs = {
+	.disable = tpg110_disable,
+	.enable = tpg110_enable,
+	.get_modes = tpg110_get_modes,
+};
+
+static int tpg110_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *backlight;
+	struct tpg110 *tpg;
+	int ret;
+
+	tpg = devm_kzalloc(dev, sizeof(*tpg), GFP_KERNEL);
+	if (!tpg)
+		return -ENOMEM;
+	tpg->dev = dev;
+
+	/* We get the physical display dimensions from the DT */
+	ret = of_property_read_u32(np, "width-mm", &tpg->width);
+	if (ret)
+		dev_err(dev, "no panel width specified\n");
+	ret = of_property_read_u32(np, "height-mm", &tpg->height);
+	if (ret)
+		dev_err(dev, "no panel height specified\n");
+
+	/* Look for some optional backlight */
+	backlight = of_parse_phandle(np, "backlight", 0);
+	if (backlight) {
+		tpg->backlight = of_find_backlight_by_node(backlight);
+		of_node_put(backlight);
+
+		if (!tpg->backlight)
+			return -EPROBE_DEFER;
+	}
+
+	/* This asserts the GRESTB signal, putting the display into reset */
+	tpg->grestb = devm_gpiod_get(dev, "grestb", GPIOD_OUT_HIGH);
+	if (IS_ERR(tpg->grestb)) {
+		dev_err(dev, "no GRESTB GPIO\n");
+		return -ENODEV;
+	}
+
+	spi->bits_per_word = 8;
+	spi->mode |= SPI_3WIRE_HIZ;
+	ret = spi_setup(spi);
+	if (ret < 0) {
+		dev_err(dev, "spi setup failed.\n");
+		return ret;
+	}
+	tpg->spi = spi;
+
+	ret = tpg110_startup(tpg);
+	if (ret)
+		return ret;
+
+	drm_panel_init(&tpg->panel);
+	tpg->panel.dev = dev;
+	tpg->panel.funcs = &tpg110_drm_funcs;
+	spi_set_drvdata(spi, tpg);
+
+	return drm_panel_add(&tpg->panel);
+}
+
+static int tpg110_remove(struct spi_device *spi)
+{
+	struct tpg110 *tpg = spi_get_drvdata(spi);
+
+	drm_panel_remove(&tpg->panel);
+	return 0;
+}
+
+static const struct of_device_id tpg110_match[] = {
+	{ .compatible = "tpo,tpg110", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, tpg110_match);
+
+static struct spi_driver tpg110_driver = {
+	.probe		= tpg110_probe,
+	.remove		= tpg110_remove,
+	.driver		= {
+		.name	= "tpo-tpg110-panel",
+		.of_match_table = tpg110_match,
+	},
+};
+module_spi_driver(tpg110_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("TPO TPG110 panel driver");
+MODULE_LICENSE("GPL v2");