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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 v3] drm/panel: Add Ilitek ILI9322 driver
Date: Fri, 22 Dec 2017 00:44:11 +0100
Message-Id: <20171221234411.12156-1-linus.walleij@linaro.org>
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Cc: Ben Dooks <ben.dooks@codethink.co.uk>,
 David Lechner <david@lechnology.com>, Stefano Babic <sbabic@denx.de>
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This adds support for the Ilitek ILI9322 QVGA (320x240)
TFT panel driver.

This panel driver supports serial or parallel RGB or
YUV input and also ITU-T BT.656 input streams.

The controller is combined with a physical panel and
configured through the device tree.

Cc: David Lechner <david@lechnology.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Ben Dooks <ben.dooks@codethink.co.uk>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
ChangeLog v2->v3:
- Fix minor checkpatch fallouts.
- Collect Thierry's ACK.
ChangeLog v1->v2:
- Dropped all DT parsing code in favor of open-coding the
  display config on a per-system basis based on system-specific
  compatible strings, after feedback from the DT maintainers.
- Define a set of configs for the D-Link DIR-685 router.
- Tested on the D-Link DIR-685.
---
 drivers/gpu/drm/panel/Kconfig                |   8 +
 drivers/gpu/drm/panel/Makefile               |   1 +
 drivers/gpu/drm/panel/panel-ilitek-ili9322.c | 962 +++++++++++++++++++++++++++
 3 files changed, 971 insertions(+)
 create mode 100644 drivers/gpu/drm/panel/panel-ilitek-ili9322.c

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index 726f3fb3312d..6ba4031f3919 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -28,6 +28,14 @@ config DRM_PANEL_SIMPLE
 	  that it can be automatically turned off when the panel goes into a
 	  low power state.
 
+config DRM_PANEL_ILITEK_IL9322
+	tristate "Ilitek ILI9322 320x240 QVGA panels"
+	depends on OF && SPI
+	select REGMAP
+	help
+	  Say Y here if you want to enable support for Ilitek IL9322
+	  QVGA (320x240) RGB, YUV and ITU-T BT.656 panels.
+
 config DRM_PANEL_INNOLUX_P079ZCA
 	tristate "Innolux P079ZCA panel"
 	depends on OF
diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
index 2c4e1a93e05f..6d251ebc568c 100644
--- a/drivers/gpu/drm/panel/Makefile
+++ b/drivers/gpu/drm/panel/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_DRM_PANEL_LVDS) += panel-lvds.o
 obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
+obj-$(CONFIG_DRM_PANEL_ILITEK_IL9322) += panel-ilitek-ili9322.o
 obj-$(CONFIG_DRM_PANEL_INNOLUX_P079ZCA) += panel-innolux-p079zca.o
 obj-$(CONFIG_DRM_PANEL_JDI_LT070ME05000) += panel-jdi-lt070me05000.o
 obj-$(CONFIG_DRM_PANEL_LG_LG4573) += panel-lg-lg4573.o
diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9322.c b/drivers/gpu/drm/panel/panel-ilitek-ili9322.c
new file mode 100644
index 000000000000..b4ec0ecff807
--- /dev/null
+++ b/drivers/gpu/drm/panel/panel-ilitek-ili9322.c
@@ -0,0 +1,962 @@
+/*
+ * Ilitek ILI9322 TFT LCD drm_panel driver.
+ *
+ * This panel can be configured to support:
+ * - 8-bit serial RGB interface
+ * - 24-bit parallel RGB interface
+ * - 8-bit ITU-R BT.601 interface
+ * - 8-bit ITU-R BT.656 interface
+ * - Up to 320RGBx240 dots resolution TFT LCD displays
+ * - Scaling, brightness and contrast
+ *
+ * The scaling means that the display accepts a 640x480 or 720x480
+ * input and rescales it to fit to the 320x240 display. So what we
+ * present to the system is something else than what comes out on the
+ * actual display.
+ *
+ * Copyright (C) 2017 Linus Walleij <linus.walleij@linaro.org>
+ * Derived from drivers/drm/gpu/panel/panel-samsung-ld9040.c
+ *
+ * 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 <drm/drmP.h>
+#include <drm/drm_panel.h>
+
+#include <linux/of_device.h>
+#include <linux/bitops.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#include <video/mipi_display.h>
+#include <video/of_videomode.h>
+#include <video/videomode.h>
+
+#define ILI9322_CHIP_ID			0x00
+#define ILI9322_CHIP_ID_MAGIC		0x96
+
+/*
+ * Voltage on the communication interface, from 0.7 (0x00)
+ * to 1.32 (0x1f) times the VREG1OUT voltage in 2% increments.
+ * 1.00 (0x0f) is the default.
+ */
+#define ILI9322_VCOM_AMP		0x01
+
+/*
+ * High voltage on the communication signals, from 0.37 (0x00) to
+ * 1.0 (0x3f) times the VREGOUT1 voltage in 1% increments.
+ * 0.83 (0x2e) is the default.
+ */
+#define ILI9322_VCOM_HIGH		0x02
+
+/*
+ * VREG1 voltage regulator from 3.6V (0x00) to 6.0V (0x18) in 0.1V
+ * increments. 5.4V (0x12) is the default. This is the reference
+ * voltage for the VCOM levels and the greyscale level.
+ */
+#define ILI9322_VREG1_VOLTAGE		0x03
+
+/* Describes the incoming signal */
+#define ILI9322_ENTRY			0x06
+/* 0 = right-to-left, 1 = left-to-right (default), horizontal flip */
+#define ILI9322_ENTRY_HDIR		BIT(0)
+/* 0 = down-to-up, 1 = up-to-down (default), vertical flip  */
+#define ILI9322_ENTRY_VDIR		BIT(1)
+/* NTSC, PAL or autodetect */
+#define ILI9322_ENTRY_NTSC		(0 << 2)
+#define ILI9322_ENTRY_PAL		(1 << 2)
+#define ILI9322_ENTRY_AUTODETECT	(3 << 2)
+/* Input format */
+#define ILI9322_ENTRY_SERIAL_RGB_THROUGH (0 << 4)
+#define ILI9322_ENTRY_SERIAL_RGB_ALIGNED (1 << 4)
+#define ILI9322_ENTRY_SERIAL_RGB_DUMMY_320X240 (2 << 4)
+#define ILI9322_ENTRY_SERIAL_RGB_DUMMY_360X240 (3 << 4)
+#define ILI9322_ENTRY_DISABLE_1		(4 << 4)
+#define ILI9322_ENTRY_PARALLEL_RGB_THROUGH (5 << 4)
+#define ILI9322_ENTRY_PARALLEL_RGB_ALIGNED (6 << 4)
+#define ILI9322_ENTRY_YUV_640Y_320CBCR_25_54_MHZ (7 << 4)
+#define ILI9322_ENTRY_YUV_720Y_360CBCR_27_MHZ (8 << 4)
+#define ILI9322_ENTRY_DISABLE_2		(9 << 4)
+#define ILI9322_ENTRY_ITU_R_BT_656_720X360 (10 << 4)
+#define ILI9322_ENTRY_ITU_R_BT_656_640X320 (11 << 4)
+
+/* Power control */
+#define ILI9322_POW_CTRL		0x07
+#define ILI9322_POW_CTRL_STB		BIT(0) /* 0 = standby, 1 = normal */
+#define ILI9322_POW_CTRL_VGL		BIT(1) /* 0 = off, 1 = on  */
+#define ILI9322_POW_CTRL_VGH		BIT(2) /* 0 = off, 1 = on  */
+#define ILI9322_POW_CTRL_DDVDH		BIT(3) /* 0 = off, 1 = on  */
+#define ILI9322_POW_CTRL_VCOM		BIT(4) /* 0 = off, 1 = on  */
+#define ILI9322_POW_CTRL_VCL		BIT(5) /* 0 = off, 1 = on  */
+#define ILI9322_POW_CTRL_AUTO		BIT(6) /* 0 = interactive, 1 = auto */
+#define ILI9322_POW_CTRL_STANDBY	(ILI9322_POW_CTRL_VGL | \
+					 ILI9322_POW_CTRL_VGH | \
+					 ILI9322_POW_CTRL_DDVDH | \
+					 ILI9322_POW_CTRL_VCL | \
+					 ILI9322_POW_CTRL_AUTO | \
+					 BIT(7))
+#define ILI9322_POW_CTRL_DEFAULT	(ILI9322_POW_CTRL_STANDBY | \
+					 ILI9322_POW_CTRL_STB)
+
+/* Vertical back porch bits 0..5 */
+#define ILI9322_VBP			0x08
+
+/* Horizontal back porch, 8 bits */
+#define ILI9322_HBP			0x09
+
+/*
+ * Polarity settings:
+ * 1 = positive polarity
+ * 0 = negative polarity
+ */
+#define ILI9322_POL			0x0a
+#define ILI9322_POL_DCLK		BIT(0) /* 1 default */
+#define ILI9322_POL_HSYNC		BIT(1) /* 0 default */
+#define ILI9322_POL_VSYNC		BIT(2) /* 0 default */
+#define ILI9322_POL_DE			BIT(3) /* 1 default */
+/*
+ * 0 means YCBCR are ordered Cb0,Y0,Cr0,Y1,Cb2,Y2,Cr2,Y3 (default)
+ *   in RGB mode this means RGB comes in RGBRGB
+ * 1 means YCBCR are ordered Cr0,Y0,Cb0,Y1,Cr2,Y2,Cb2,Y3
+ *   in RGB mode this means RGB comes in BGRBGR
+ */
+#define ILI9322_POL_YCBCR_MODE		BIT(4)
+/* Formula A for YCbCR->RGB = 0, Formula B = 1 */
+#define ILI9322_POL_FORMULA		BIT(5)
+/* Reverse polarity: 0 = 0..255, 1 = 255..0 */
+#define ILI9322_POL_REV			BIT(6)
+
+#define ILI9322_IF_CTRL			0x0b
+#define ILI9322_IF_CTRL_HSYNC_VSYNC	0x00
+#define ILI9322_IF_CTRL_HSYNC_VSYNC_DE	BIT(2)
+#define ILI9322_IF_CTRL_DE_ONLY		BIT(3)
+#define ILI9322_IF_CTRL_SYNC_DISABLED	(BIT(2) | BIT(3))
+#define ILI9322_IF_CTRL_LINE_INVERSION	BIT(0) /* Not set means frame inv */
+
+#define ILI9322_GLOBAL_RESET		0x04
+#define ILI9322_GLOBAL_RESET_ASSERT	0x00 /* bit 0 = 0 -> reset */
+
+/*
+ * 4+4 bits of negative and positive gamma correction
+ * Upper nybble, bits 4-7 are negative gamma
+ * Lower nybble, bits 0-3 are positive gamma
+ */
+#define ILI9322_GAMMA_1			0x10
+#define ILI9322_GAMMA_2			0x11
+#define ILI9322_GAMMA_3			0x12
+#define ILI9322_GAMMA_4			0x13
+#define ILI9322_GAMMA_5			0x14
+#define ILI9322_GAMMA_6			0x15
+#define ILI9322_GAMMA_7			0x16
+#define ILI9322_GAMMA_8			0x17
+
+/**
+ * enum ili9322_input - the format of the incoming signal to the panel
+ *
+ * The panel can be connected to various input streams and four of them can
+ * be selected by electronic straps on the display. However it is possible
+ * to select another mode or override the electronic default with this
+ * setting.
+ */
+enum ili9322_input {
+	ILI9322_INPUT_SRGB_THROUGH = 0x0,
+	ILI9322_INPUT_SRGB_ALIGNED = 0x1,
+	ILI9322_INPUT_SRGB_DUMMY_320X240 = 0x2,
+	ILI9322_INPUT_SRGB_DUMMY_360X240 = 0x3,
+	ILI9322_INPUT_DISABLED_1 = 0x4,
+	ILI9322_INPUT_PRGB_THROUGH = 0x5,
+	ILI9322_INPUT_PRGB_ALIGNED = 0x6,
+	ILI9322_INPUT_YUV_640X320_YCBCR = 0x7,
+	ILI9322_INPUT_YUV_720X360_YCBCR = 0x8,
+	ILI9322_INPUT_DISABLED_2 = 0x9,
+	ILI9322_INPUT_ITU_R_BT656_720X360_YCBCR = 0xa,
+	ILI9322_INPUT_ITU_R_BT656_640X320_YCBCR = 0xb,
+	ILI9322_INPUT_UNKNOWN = 0xc,
+};
+
+const char *ili9322_inputs[] = {
+	"8 bit serial RGB through",
+	"8 bit serial RGB aligned",
+	"8 bit serial RGB dummy 320x240",
+	"8 bit serial RGB dummy 360x240",
+	"disabled 1",
+	"24 bit parallel RGB through",
+	"24 bit parallel RGB aligned",
+	"24 bit YUV 640Y 320CbCr",
+	"24 bit YUV 720Y 360CbCr",
+	"disabled 2",
+	"8 bit ITU-R BT.656 720Y 360CbCr",
+	"8 bit ITU-R BT.656 640Y 320CbCr",
+};
+
+/**
+ * struct ili9322_config - the system specific ILI9322 configuration
+ * @width_mm: physical panel width [mm]
+ * @height_mm: physical panel height [mm]
+ * @flip_horizontal: flip the image horizontally (right-to-left scan)
+ * (only in RGB and YUV modes)
+ * @flip_vertical: flip the image vertically (down-to-up scan)
+ * (only in RGB and YUV modes)
+ * @input: the input/entry type used in this system, if this is set to
+ * ILI9322_INPUT_UNKNOWN the driver will try to figure it out by probing
+ * the hardware
+ * @vreg1out_mv: the output in microvolts for the VREGOUT1 regulator used
+ * to drive the physical display. Valid ranges are 3600 thru 6000 in 100
+ * microvolt increments. If not specified, hardware defaults will be
+ * used (4.5V).
+ * @vcom_high_percent: the percentage of VREGOUT1 used for the peak
+ * voltage on the communications link. Valid ranges are 37 thru 100
+ * percent. If not specified, hardware defaults will be used (91%).
+ * @vcom_amplitude_percent: the percentage of VREGOUT1 used for the
+ * peak-to-peak amplitude of the communcation signals to the physical
+ * display. Valid ranges are 70 thru 132 percent in increments if two
+ * percent. Odd percentages will be truncated. If not specified, hardware
+ * defaults will be used (114%).
+ * @dclk_active_high: data/pixel clock active high, data will be clocked
+ * in on the rising edge of the DCLK (this is usually the case).
+ * @syncmode: The synchronization mode, what sync signals are emitted.
+ * See the enum for details.
+ * @de_active_high: DE (data entry) is active high
+ * @hsync_active_high: HSYNC is active high
+ * @vsync_active_high: VSYNC is active high
+ * @gamma_corr_pos: a set of 8 nybbles describing positive
+ * gamma correction for voltages V1 thru V8. Valid range 0..15
+ * @gamma_corr_neg: a set of 8 nybbles describing negative
+ * gamma correction for voltages V1 thru V8. Valid range 0..15
+ *
+ * These adjust what grayscale voltage will be output for input data V1 = 0,
+ * V2 = 16, V3 = 48, V4 = 96, V5 = 160, V6 = 208, V7 = 240 and V8 = 255.
+ * The curve is shaped like this:
+ *
+ *  ^
+ *  |                                                        V8
+ *  |                                                   V7
+ *  |                                          V6
+ *  |                               V5
+ *  |                    V4
+ *  |            V3
+ *  |     V2
+ *  | V1
+ *  +----------------------------------------------------------->
+ *    0   16     48      96         160        208      240  255
+ *
+ * The negative and postive gamma values adjust the V1 thru V8 up/down
+ * according to the datasheet specifications. This is a property of the
+ * physical display connected to the display controller and may vary.
+ * If defined, both arrays must be supplied in full. If the properties
+ * are not supplied, hardware defaults will be used.
+ */
+struct ili9322_config {
+	u32 width_mm;
+	u32 height_mm;
+	bool flip_horizontal;
+	bool flip_vertical;
+	enum ili9322_input input;
+	u32 vreg1out_mv;
+	u32 vcom_high_percent;
+	u32 vcom_amplitude_percent;
+	bool dclk_active_high;
+	bool de_active_high;
+	bool hsync_active_high;
+	bool vsync_active_high;
+	u8 syncmode;
+	u8 gamma_corr_pos[8];
+	u8 gamma_corr_neg[8];
+};
+
+struct ili9322 {
+	struct device *dev;
+	const struct ili9322_config *conf;
+	struct drm_panel panel;
+	struct regmap *regmap;
+	struct regulator_bulk_data supplies[3];
+	struct gpio_desc *reset_gpio;
+	enum ili9322_input input;
+	struct videomode vm;
+	u8 gamma[8];
+	u8 vreg1out;
+	u8 vcom_high;
+	u8 vcom_amplitude;
+};
+
+static inline struct ili9322 *panel_to_ili9322(struct drm_panel *panel)
+{
+	return container_of(panel, struct ili9322, panel);
+}
+
+static int ili9322_regmap_spi_write(void *context, const void *data,
+				    size_t count)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+	u8 buf[2];
+
+	/* Clear bit 7 to write */
+	memcpy(buf, data, 2);
+	buf[0] &= ~0x80;
+
+	dev_dbg(dev, "WRITE: %02x %02x\n", buf[0], buf[1]);
+	return spi_write_then_read(spi, buf, 2, NULL, 0);
+}
+
+static int ili9322_regmap_spi_read(void *context, const void *reg,
+				   size_t reg_size, void *val, size_t val_size)
+{
+	struct device *dev = context;
+	struct spi_device *spi = to_spi_device(dev);
+	u8 buf[1];
+
+	/* Set bit 7 to 1 to read */
+	memcpy(buf, reg, 1);
+	dev_dbg(dev, "READ: %02x reg size = %zu, val size = %zu\n",
+		buf[0], reg_size, val_size);
+	buf[0] |= 0x80;
+
+	return spi_write_then_read(spi, buf, 1, val, 1);
+}
+
+static struct regmap_bus ili9322_regmap_bus = {
+	.write = ili9322_regmap_spi_write,
+	.read = ili9322_regmap_spi_read,
+	.reg_format_endian_default = REGMAP_ENDIAN_BIG,
+	.val_format_endian_default = REGMAP_ENDIAN_BIG,
+};
+
+static bool ili9322_volatile_reg(struct device *dev, unsigned int reg)
+{
+	return false;
+}
+
+static bool ili9322_writeable_reg(struct device *dev, unsigned int reg)
+{
+	/* Just register 0 is read-only */
+	if (reg == 0x00)
+		return false;
+	return true;
+}
+
+const struct regmap_config ili9322_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0x44,
+	.cache_type = REGCACHE_RBTREE,
+	.volatile_reg = ili9322_volatile_reg,
+	.writeable_reg = ili9322_writeable_reg,
+};
+
+static int ili9322_init(struct drm_panel *panel, struct ili9322 *ili)
+{
+	struct drm_connector *connector = panel->connector;
+	u8 reg;
+	int ret;
+	int i;
+
+	/* Reset display */
+	ret = regmap_write(ili->regmap, ILI9322_GLOBAL_RESET,
+			   ILI9322_GLOBAL_RESET_ASSERT);
+	if (ret) {
+		dev_err(ili->dev, "can't issue GRESET (%d)\n", ret);
+		return ret;
+	}
+
+	/* Set up the main voltage regulator */
+	if (ili->vreg1out != U8_MAX) {
+		ret = regmap_write(ili->regmap, ILI9322_VREG1_VOLTAGE,
+				   ili->vreg1out);
+		if (ret) {
+			dev_err(ili->dev, "can't set up VREG1OUT (%d)\n", ret);
+			return ret;
+		}
+	}
+
+	if (ili->vcom_amplitude != U8_MAX) {
+		ret = regmap_write(ili->regmap, ILI9322_VCOM_AMP,
+				   ili->vcom_amplitude);
+		if (ret) {
+			dev_err(ili->dev,
+				"can't set up VCOM amplitude (%d)\n", ret);
+			return ret;
+		}
+	};
+
+	if (ili->vcom_high != U8_MAX) {
+		ret = regmap_write(ili->regmap, ILI9322_VCOM_HIGH,
+				   ili->vcom_high);
+		if (ret) {
+			dev_err(ili->dev, "can't set up VCOM high (%d)\n", ret);
+			return ret;
+		}
+	};
+
+	/* Set up gamma correction */
+	for (i = 0; i < ARRAY_SIZE(ili->gamma); i++) {
+		ret = regmap_write(ili->regmap, ILI9322_GAMMA_1 + i,
+				   ili->gamma[i]);
+		if (ret) {
+			dev_err(ili->dev,
+				"can't write gamma V%d to 0x%02x (%d)\n",
+				i + 1, ILI9322_GAMMA_1 + i, ret);
+			return ret;
+		}
+	}
+
+	/*
+	 * Polarity and inverted color order for RGB input.
+	 * None of this applies in the BT.656 mode.
+	 */
+	if (ili->conf->dclk_active_high) {
+		reg = ILI9322_POL_DCLK;
+		connector->display_info.bus_flags |=
+			DRM_BUS_FLAG_PIXDATA_POSEDGE;
+	} else {
+		reg = 0;
+		connector->display_info.bus_flags |=
+			DRM_BUS_FLAG_PIXDATA_NEGEDGE;
+	}
+	if (ili->conf->de_active_high) {
+		reg |= ILI9322_POL_DE;
+		connector->display_info.bus_flags |=
+			DRM_BUS_FLAG_DE_HIGH;
+	} else {
+		connector->display_info.bus_flags |=
+			DRM_BUS_FLAG_DE_LOW;
+	}
+	if (ili->conf->hsync_active_high)
+		reg |= ILI9322_POL_HSYNC;
+	if (ili->conf->vsync_active_high)
+		reg |= ILI9322_POL_VSYNC;
+	ret = regmap_write(ili->regmap, ILI9322_POL, reg);
+	if (ret) {
+		dev_err(ili->dev, "can't write POL register (%d)\n", ret);
+		return ret;
+	}
+
+	/*
+	 * Set up interface control.
+	 * This is not used in the BT.656 mode (no H/Vsync or DE signals).
+	 */
+	reg = ili->conf->syncmode;
+	reg |= ILI9322_IF_CTRL_LINE_INVERSION;
+	ret = regmap_write(ili->regmap, ILI9322_IF_CTRL, reg);
+	if (ret) {
+		dev_err(ili->dev, "can't write IF CTRL register (%d)\n", ret);
+		return ret;
+	}
+
+	/* Set up the input mode */
+	reg = (ili->input << 4);
+	/* These are inverted, setting to 1 is the default, clearing flips */
+	if (!ili->conf->flip_horizontal)
+		reg |= ILI9322_ENTRY_HDIR;
+	if (!ili->conf->flip_vertical)
+		reg |= ILI9322_ENTRY_VDIR;
+	reg |= ILI9322_ENTRY_AUTODETECT;
+	ret = regmap_write(ili->regmap, ILI9322_ENTRY, reg);
+	if (ret) {
+		dev_err(ili->dev, "can't write ENTRY reg (%d)\n", ret);
+		return ret;
+	}
+	dev_info(ili->dev, "display is in %s mode, syncmode %02x\n",
+		 ili9322_inputs[ili->input],
+		 ili->conf->syncmode);
+
+	dev_info(ili->dev, "initialized display\n");
+
+	return 0;
+}
+
+/*
+ * This power-on sequence if from the datasheet, page 57.
+ */
+static int ili9322_power_on(struct ili9322 *ili)
+{
+	int ret;
+
+	/* Assert RESET */
+	gpiod_set_value(ili->reset_gpio, 1);
+
+	ret = regulator_bulk_enable(ARRAY_SIZE(ili->supplies), ili->supplies);
+	if (ret < 0) {
+		dev_err(ili->dev, "unable to enable regulators\n");
+		return ret;
+	}
+	msleep(20);
+
+	/* De-assert RESET */
+	gpiod_set_value(ili->reset_gpio, 0);
+
+	msleep(10);
+
+	return 0;
+}
+
+static int ili9322_power_off(struct ili9322 *ili)
+{
+	return regulator_bulk_disable(ARRAY_SIZE(ili->supplies), ili->supplies);
+}
+
+static int ili9322_disable(struct drm_panel *panel)
+{
+	struct ili9322 *ili = panel_to_ili9322(panel);
+	int ret;
+
+	ret = regmap_write(ili->regmap, ILI9322_POW_CTRL,
+			   ILI9322_POW_CTRL_STANDBY);
+	if (ret) {
+		dev_err(ili->dev, "unable to go to standby mode\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int ili9322_unprepare(struct drm_panel *panel)
+{
+	struct ili9322 *ili = panel_to_ili9322(panel);
+
+	return ili9322_power_off(ili);
+}
+
+static int ili9322_prepare(struct drm_panel *panel)
+{
+	struct ili9322 *ili = panel_to_ili9322(panel);
+	int ret;
+
+	ret = ili9322_power_on(ili);
+	if (ret < 0)
+		return ret;
+
+	ret = ili9322_init(panel, ili);
+	if (ret < 0)
+		ili9322_unprepare(panel);
+
+	return ret;
+}
+
+static int ili9322_enable(struct drm_panel *panel)
+{
+	struct ili9322 *ili = panel_to_ili9322(panel);
+	int ret;
+
+	ret = regmap_write(ili->regmap, ILI9322_POW_CTRL,
+			   ILI9322_POW_CTRL_DEFAULT);
+	if (ret) {
+		dev_err(ili->dev, "unable to enable panel\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+/* Serial RGB modes */
+static const struct drm_display_mode srgb_320x240_mode = {
+	.clock = 2453500,
+	.hdisplay = 320,
+	.hsync_start = 320 + 359,
+	.hsync_end = 320 + 359 + 1,
+	.htotal = 320 + 359 + 1 + 241,
+	.vdisplay = 240,
+	.vsync_start = 240 + 4,
+	.vsync_end = 240 + 4 + 1,
+	.vtotal = 262,
+	.vrefresh = 60,
+	.flags = 0,
+};
+
+static const struct drm_display_mode srgb_360x240_mode = {
+	.clock = 2700000,
+	.hdisplay = 360,
+	.hsync_start = 360 + 35,
+	.hsync_end = 360 + 35 + 1,
+	.htotal = 360 + 35 + 1 + 241,
+	.vdisplay = 240,
+	.vsync_start = 240 + 21,
+	.vsync_end = 240 + 21 + 1,
+	.vtotal = 262,
+	.vrefresh = 60,
+	.flags = 0,
+};
+
+/* This is the only mode listed for parallel RGB in the datasheet */
+static const struct drm_display_mode prgb_320x240_mode = {
+	.clock = 6400000,
+	.hdisplay = 320,
+	.hsync_start = 320 + 38,
+	.hsync_end = 320 + 38 + 1,
+	.htotal = 320 + 38 + 1 + 50,
+	.vdisplay = 240,
+	.vsync_start = 240 + 4,
+	.vsync_end = 240 + 4 + 1,
+	.vtotal = 262,
+	.vrefresh = 60,
+	.flags = 0,
+};
+
+/* YUV modes */
+static const struct drm_display_mode yuv_640x320_mode = {
+	.clock = 2454000,
+	.hdisplay = 640,
+	.hsync_start = 640 + 252,
+	.hsync_end = 640 + 252 + 1,
+	.htotal = 640 + 252 + 1 + 28,
+	.vdisplay = 320,
+	.vsync_start = 320 + 4,
+	.vsync_end = 320 + 4 + 1,
+	.vtotal = 320 + 4 + 1 + 18,
+	.vrefresh = 60,
+	.flags = 0,
+};
+
+static const struct drm_display_mode yuv_720x360_mode = {
+	.clock = 2700000,
+	.hdisplay = 720,
+	.hsync_start = 720 + 252,
+	.hsync_end = 720 + 252 + 1,
+	.htotal = 720 + 252 + 1 + 24,
+	.vdisplay = 360,
+	.vsync_start = 360 + 4,
+	.vsync_end = 360 + 4 + 1,
+	.vtotal = 360 + 4 + 1 + 18,
+	.vrefresh = 60,
+	.flags = 0,
+};
+
+/* BT.656 VGA mode, 640x480 */
+static const struct drm_display_mode itu_r_bt_656_640_mode = {
+	.clock = 2454000,
+	.hdisplay = 640,
+	.hsync_start = 640 + 3,
+	.hsync_end = 640 + 3 + 1,
+	.htotal = 640 + 3 + 1 + 272,
+	.vdisplay = 480,
+	.vsync_start = 480 + 4,
+	.vsync_end = 480 + 4 + 1,
+	.vtotal = 500,
+	.vrefresh = 60,
+	.flags = 0,
+};
+
+/* BT.656 D1 mode 720x480 */
+static const struct drm_display_mode itu_r_bt_656_720_mode = {
+	.clock = 2700000,
+	.hdisplay = 720,
+	.hsync_start = 720 + 3,
+	.hsync_end = 720 + 3 + 1,
+	.htotal = 720 + 3 + 1 + 272,
+	.vdisplay = 480,
+	.vsync_start = 480 + 4,
+	.vsync_end = 480 + 4 + 1,
+	.vtotal = 500,
+	.vrefresh = 60,
+	.flags = 0,
+};
+
+static int ili9322_get_modes(struct drm_panel *panel)
+{
+	struct drm_connector *connector = panel->connector;
+	struct ili9322 *ili = panel_to_ili9322(panel);
+	struct drm_display_mode *mode;
+
+	strncpy(connector->display_info.name, "ILI9322 TFT LCD driver\0",
+		DRM_DISPLAY_INFO_LEN);
+	connector->display_info.width_mm = ili->conf->width_mm;
+	connector->display_info.height_mm = ili->conf->height_mm;
+
+	switch (ili->input) {
+	case ILI9322_INPUT_SRGB_DUMMY_320X240:
+		mode = drm_mode_duplicate(panel->drm, &srgb_320x240_mode);
+		break;
+	case ILI9322_INPUT_SRGB_DUMMY_360X240:
+		mode = drm_mode_duplicate(panel->drm, &srgb_360x240_mode);
+		break;
+	case ILI9322_INPUT_PRGB_THROUGH:
+	case ILI9322_INPUT_PRGB_ALIGNED:
+		mode = drm_mode_duplicate(panel->drm, &prgb_320x240_mode);
+		break;
+	case ILI9322_INPUT_YUV_640X320_YCBCR:
+		mode = drm_mode_duplicate(panel->drm, &yuv_640x320_mode);
+		break;
+	case ILI9322_INPUT_YUV_720X360_YCBCR:
+		mode = drm_mode_duplicate(panel->drm, &yuv_720x360_mode);
+		break;
+	case ILI9322_INPUT_ITU_R_BT656_720X360_YCBCR:
+		mode = drm_mode_duplicate(panel->drm, &itu_r_bt_656_720_mode);
+		break;
+	case ILI9322_INPUT_ITU_R_BT656_640X320_YCBCR:
+		mode = drm_mode_duplicate(panel->drm, &itu_r_bt_656_640_mode);
+		break;
+	default:
+		mode = NULL;
+		break;
+	}
+	if (!mode) {
+		DRM_ERROR("bad mode or failed to add mode\n");
+		return -EINVAL;
+	}
+	drm_mode_set_name(mode);
+	/*
+	 * This is the preferred mode because most people are going
+	 * to want to use the display with VGA type graphics.
+	 */
+	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+
+	/* Set up the polarity */
+	if (ili->conf->hsync_active_high)
+		mode->flags |= DRM_MODE_FLAG_PHSYNC;
+	else
+		mode->flags |= DRM_MODE_FLAG_NHSYNC;
+	if (ili->conf->vsync_active_high)
+		mode->flags |= DRM_MODE_FLAG_PVSYNC;
+	else
+		mode->flags |= DRM_MODE_FLAG_NVSYNC;
+
+	mode->width_mm = ili->conf->width_mm;
+	mode->height_mm = ili->conf->height_mm;
+	drm_mode_probed_add(connector, mode);
+
+	return 1; /* Number of modes */
+}
+
+static const struct drm_panel_funcs ili9322_drm_funcs = {
+	.disable = ili9322_disable,
+	.unprepare = ili9322_unprepare,
+	.prepare = ili9322_prepare,
+	.enable = ili9322_enable,
+	.get_modes = ili9322_get_modes,
+};
+
+static int ili9322_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct ili9322 *ili;
+	const struct regmap_config *regmap_config;
+	u8 gamma;
+	u32 val;
+	int ret;
+	int i;
+
+	ili = devm_kzalloc(dev, sizeof(struct ili9322), GFP_KERNEL);
+	if (!ili)
+		return -ENOMEM;
+
+	spi_set_drvdata(spi, ili);
+
+	ili->dev = dev;
+
+	/*
+	 * Every new incarnation of this display must have a unique
+	 * data entry for the system in this driver.
+	 */
+	ili->conf = of_device_get_match_data(dev);
+	if (!ili->conf) {
+		dev_err(dev, "missing device configuration\n");
+		return -ENODEV;
+	}
+
+	val = ili->conf->vreg1out_mv;
+	if (!val) {
+		/* Default HW value, do not touch (should be 4.5V) */
+		ili->vreg1out = U8_MAX;
+	} else {
+		if (val < 3600) {
+			dev_err(dev, "too low VREG1OUT\n");
+			return -EINVAL;
+		}
+		if (val > 6000) {
+			dev_err(dev, "too high VREG1OUT\n");
+			return -EINVAL;
+		}
+		if ((val % 100) != 0) {
+			dev_err(dev, "VREG1OUT is no even 100 microvolt\n");
+			return -EINVAL;
+		}
+		val -= 3600;
+		val /= 100;
+		dev_dbg(dev, "VREG1OUT = 0x%02x\n", val);
+		ili->vreg1out = val;
+	}
+
+	val = ili->conf->vcom_high_percent;
+	if (!val) {
+		/* Default HW value, do not touch (should be 91%) */
+		ili->vcom_high = U8_MAX;
+	} else {
+		if (val < 37) {
+			dev_err(dev, "too low VCOM high\n");
+			return -EINVAL;
+		}
+		if (val > 100) {
+			dev_err(dev, "too high VCOM high\n");
+			return -EINVAL;
+		}
+		val -= 37;
+		dev_dbg(dev, "VCOM high = 0x%02x\n", val);
+		ili->vcom_high = val;
+	}
+
+	val = ili->conf->vcom_amplitude_percent;
+	if (!val) {
+		/* Default HW value, do not touch (should be 114%) */
+		ili->vcom_high = U8_MAX;
+	} else {
+		if (val < 70) {
+			dev_err(dev, "too low VCOM amplitude\n");
+			return -EINVAL;
+		}
+		if (val > 132) {
+			dev_err(dev, "too high VCOM amplitude\n");
+			return -EINVAL;
+		}
+		val -= 70;
+		val >>= 1; /* Increments of 2% */
+		dev_dbg(dev, "VCOM amplitude = 0x%02x\n", val);
+		ili->vcom_amplitude = val;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(ili->gamma); i++) {
+		val = ili->conf->gamma_corr_neg[i];
+		if (val > 15) {
+			dev_err(dev, "negative gamma %u > 15, capping\n", val);
+			val = 15;
+		}
+		gamma = val << 4;
+		val = ili->conf->gamma_corr_pos[i];
+		if (val > 15) {
+			dev_err(dev, "positive gamma %u > 15, capping\n", val);
+			val = 15;
+		}
+		gamma |= val;
+		ili->gamma[i] = gamma;
+		dev_dbg(dev, "gamma V%d: 0x%02x\n", i + 1, gamma);
+	}
+
+	ili->supplies[0].supply = "vcc"; /* 2.7-3.6 V */
+	ili->supplies[1].supply = "iovcc"; /* 1.65-3.6V */
+	ili->supplies[2].supply = "vci"; /* 2.7-3.6V */
+	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ili->supplies),
+				      ili->supplies);
+	if (ret < 0)
+		return ret;
+	ret = regulator_set_voltage(ili->supplies[0].consumer,
+				    2700000, 3600000);
+	if (ret)
+		return ret;
+	ret = regulator_set_voltage(ili->supplies[1].consumer,
+				    1650000, 3600000);
+	if (ret)
+		return ret;
+	ret = regulator_set_voltage(ili->supplies[2].consumer,
+				    2700000, 3600000);
+	if (ret)
+		return ret;
+
+	ili->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ili->reset_gpio)) {
+		dev_err(dev, "failed to get RESET GPIO\n");
+		return PTR_ERR(ili->reset_gpio);
+	}
+
+	spi->bits_per_word = 8;
+	ret = spi_setup(spi);
+	if (ret < 0) {
+		dev_err(dev, "spi setup failed.\n");
+		return ret;
+	}
+	regmap_config = &ili9322_regmap_config;
+	ili->regmap = devm_regmap_init(dev, &ili9322_regmap_bus, dev,
+				       regmap_config);
+	if (IS_ERR(ili->regmap)) {
+		dev_err(dev, "failed to allocate register map\n");
+		return PTR_ERR(ili->regmap);
+	}
+
+	ret = regmap_read(ili->regmap, ILI9322_CHIP_ID, &val);
+	if (ret) {
+		dev_err(dev, "can't get chip ID (%d)\n", ret);
+		return ret;
+	}
+	if (val != ILI9322_CHIP_ID_MAGIC) {
+		dev_err(dev, "chip ID 0x%0x2, expected 0x%02x\n", val,
+			ILI9322_CHIP_ID_MAGIC);
+		return -ENODEV;
+	}
+
+	/* Probe the system to find the display setting */
+	if (ili->conf->input == ILI9322_INPUT_UNKNOWN) {
+		ret = regmap_read(ili->regmap, ILI9322_ENTRY, &val);
+		if (ret) {
+			dev_err(dev, "can't get entry setting (%d)\n", ret);
+			return ret;
+		}
+		/* Input enum corresponds to HW setting */
+		ili->input = (val >> 4) & 0x0f;
+		if (ili->input >= ILI9322_INPUT_UNKNOWN)
+			ili->input = ILI9322_INPUT_UNKNOWN;
+	} else {
+		ili->input = ili->conf->input;
+	}
+
+	drm_panel_init(&ili->panel);
+	ili->panel.dev = dev;
+	ili->panel.funcs = &ili9322_drm_funcs;
+
+	return drm_panel_add(&ili->panel);
+}
+
+static int ili9322_remove(struct spi_device *spi)
+{
+	struct ili9322 *ili = spi_get_drvdata(spi);
+
+	ili9322_power_off(ili);
+	drm_panel_remove(&ili->panel);
+
+	return 0;
+}
+
+/*
+ * The D-Link DIR-685 panel is marked LM918A01-1A SY-B4-091116-E0199
+ */
+static const struct ili9322_config ili9322_dir_685 = {
+	.width_mm = 65,
+	.height_mm = 50,
+	.input = ILI9322_INPUT_ITU_R_BT656_640X320_YCBCR,
+	.vreg1out_mv = 4600,
+	.vcom_high_percent = 91,
+	.vcom_amplitude_percent = 114,
+	.syncmode = ILI9322_IF_CTRL_SYNC_DISABLED,
+	.dclk_active_high = true,
+	.gamma_corr_neg = { 0xa, 0x5, 0x7, 0x7, 0x7, 0x5, 0x1, 0x6 },
+	.gamma_corr_pos = { 0x7, 0x7, 0x3, 0x2, 0x3, 0x5, 0x7, 0x2 },
+};
+
+static const struct of_device_id ili9322_of_match[] = {
+	{
+		.compatible = "dlink,dir-685-panel",
+		.data = &ili9322_dir_685,
+	},
+	{
+		.compatible = "ilitek,ili9322",
+		.data = NULL,
+	},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, ili9322_of_match);
+
+static struct spi_driver ili9322_driver = {
+	.probe = ili9322_probe,
+	.remove = ili9322_remove,
+	.driver = {
+		.name = "panel-ilitek-ili9322",
+		.of_match_table = ili9322_of_match,
+	},
+};
+module_spi_driver(ili9322_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("ILI9322 LCD panel driver");
+MODULE_LICENSE("GPL v2");