drm/panel: Add support for Olimex LCD-OLinuXino panel

This patch adds Olimex Ltd. LCD-OLinuXino bridge panel driver. The panel
is used with different LCDs (currently from 480x272 to 1280x800). A
small EEPROM chip is used for identification, which holds some factory
data and timing requirements.

Signed-off-by: Stefan Mavrodiev <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Documentation/devicetree/bindings/display/panel/olimex,lcd-olinuxino.txt

···
+Binding for Olimex Ltd. LCD-OLinuXino bridge panel.
+
+This device can be used as bridge between a host controller and LCD panels.
+Currently supported LCDs are:
+  - LCD-OLinuXino-4.3TS
+  - LCD-OLinuXino-5
+  - LCD-OLinuXino-7
+  - LCD-OLinuXino-10
+
+The panel itself contains:
+  - AT24C16C EEPROM holding panel identification and timing requirements
+  - AR1021 resistive touch screen controller (optional)
+  - FT5x6 capacitive touch screnn controller (optional)
+  - GT911/GT928 capacitive touch screen controller (optional)
+
+The above chips share same I2C bus. The EEPROM is factory preprogrammed with
+device information (id, serial, etc.) and timing requirements.
+
+Touchscreen bingings can be found in these files:
+  - input/touchscreen/goodix.txt
+  - input/touchscreen/edt-ft5x06.txt
+  - input/touchscreen/ar1021.txt
+
+Required properties:
+  - compatible: should be "olimex,lcd-olinuxino"
+  - reg: address of the configuration EEPROM, should be <0x50>
+  - power-supply: phandle of the regulator that provides the supply voltage
+
+Optional properties:
+  - enable-gpios: GPIO pin to enable or disable the panel
+  - backlight: phandle of the backlight device attacked to the panel
+
+Example:
+&i2c2 {
+	panel@50 {
+		compatible = "olimex,lcd-olinuxino";
+		reg = <0x50>;
+		power-supply = <&reg_vcc5v0>;
+		enable-gpios = <&pio 7 8 GPIO_ACTIVE_HIGH>;
+		backlight = <&backlight>;
+	};
+};

MAINTAINERS

···
 F:	drivers/gpu/drm/nouveau/
 F:	include/uapi/drm/nouveau_drm.h
 
+DRM DRIVER FOR OLIMEX LCD-OLINUXINO PANELS
+M:	Stefan Mavrodiev <[e-mail]>
+S:	Maintained
+F:	drivers/gpu/drm/panel/panel-olimex-lcd-olinuxino.c
+F:	Documentation/devicetree/bindings/display/panel/olimex,lcd-olinuxino.txt
+
 DRM DRIVER FOR PERVASIVE DISPLAYS REPAPER PANELS
 M:	Noralf Trønnes <[e-mail]>
 S:	Maintained

drivers/gpu/drm/panel/Kconfig

···
 	  Say Y here if you want to enable support for LG4573 RGB panel.
 	  To compile this driver as a module, choose M here.
 
+config DRM_PANEL_OLIMEX_LCD_OLINUXINO
+	tristate "Olimex LCD-OLinuXino panel"
+	depends on OF
+	depends on I2C
+	depends on BACKLIGHT_CLASS_DEVICE
+	help
+	  The panel is used with different sizes LCDs, from 480x272 to
+	  1280x800, and 24 bit per pixel.
+
+	  Say Y here if you want to enable support for Olimex Ltd.
+	  LCD-OLinuXino panel.
+
 config DRM_PANEL_ORISETECH_OTM8009A
 	tristate "Orise Technology otm8009a 480x800 dsi 2dl panel"
 	depends on OF

drivers/gpu/drm/panel/Makefile

···
 obj-$(CONFIG_DRM_PANEL_INNOLUX_P079ZCA) += panel-innolux-p079zca.o
 obj-$(CONFIG_DRM_PANEL_JDI_LT070ME05000) += panel-jdi-lt070me05000.o
 obj-$(CONFIG_DRM_PANEL_LG_LG4573) += panel-lg-lg4573.o
+obj-$(CONFIG_DRM_PANEL_OLIMEX_LCD_OLINUXINO) += panel-olimex-lcd-olinuxino.o
 obj-$(CONFIG_DRM_PANEL_ORISETECH_OTM8009A) += panel-orisetech-otm8009a.o
 obj-$(CONFIG_DRM_PANEL_PANASONIC_VVX10F034N00) += panel-panasonic-vvx10f034n00.o
 obj-$(CONFIG_DRM_PANEL_RASPBERRYPI_TOUCHSCREEN) += panel-raspberrypi-touchscreen.o

drivers/gpu/drm/panel/panel-olimex-lcd-olinuxino.c

···
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * LCD-OLinuXino support for panel driver
+ *
+ * Copyright (C) 2018 Olimex Ltd.
+ *   Author: Stefan Mavrodiev <[e-mail]>
+ */
+
+#include <linux/backlight.h>
+#include <linux/crc32.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/regulator/consumer.h>
+
+#include <drm/drm_modes.h>
+#include <drm/drm_panel.h>
+#include <drm/drmP.h>
+
+#include <video/videomode.h>
+#include <video/display_timing.h>
+
+#define LCD_OLINUXINO_HEADER_MAGIC	0x4F4CB727
+#define LCD_OLINUXINO_DATA_LEN		256
+
+struct lcd_olinuxino_mode {
+	u32 pixelclock;
+	u32 hactive;
+	u32 hfp;
+	u32 hbp;
+	u32 hpw;
+	u32 vactive;
+	u32 vfp;
+	u32 vbp;
+	u32 vpw;
+	u32 refresh;
+	u32 flags;
+};
+
+struct lcd_olinuxino_info {
+	char name[32];
+	u32 width_mm;
+	u32 height_mm;
+	u32 bpc;
+	u32 bus_format;
+	u32 bus_flag;
+} __attribute__((__packed__));
+
+struct lcd_olinuxino_eeprom {
+	u32 header;
+	u32 id;
+	char revision[4];
+	u32 serial;
+	struct lcd_olinuxino_info info;
+	u32 num_modes;
+	u8 reserved[180];
+	u32 checksum;
+} __attribute__((__packed__));
+
+struct lcd_olinuxino {
+	struct drm_panel panel;
+	struct device *dev;
+	struct i2c_client *client;
+	struct mutex mutex;
+
+	bool prepared;
+	bool enabled;
+
+	struct backlight_device *backlight;
+	struct regulator *supply;
+	struct gpio_desc *enable_gpio;
+
+	struct lcd_olinuxino_eeprom eeprom;
+};
+
+static inline struct lcd_olinuxino *to_lcd_olinuxino(struct drm_panel *panel)
+{
+	return container_of(panel, struct lcd_olinuxino, panel);
+}
+
+static int lcd_olinuxino_disable(struct drm_panel *panel)
+{
+	struct lcd_olinuxino *lcd = to_lcd_olinuxino(panel);
+
+	if (!lcd->enabled)
+		return 0;
+
+	backlight_disable(lcd->backlight);
+
+	lcd->enabled = false;
+
+	return 0;
+}
+
+static int lcd_olinuxino_unprepare(struct drm_panel *panel)
+{
+	struct lcd_olinuxino *lcd = to_lcd_olinuxino(panel);
+
+	if (!lcd->prepared)
+		return 0;
+
+	gpiod_set_value_cansleep(lcd->enable_gpio, 0);
+	regulator_disable(lcd->supply);
+
+	lcd->prepared = false;
+
+	return 0;
+}
+
+static int lcd_olinuxino_prepare(struct drm_panel *panel)
+{
+	struct lcd_olinuxino *lcd = to_lcd_olinuxino(panel);
+	int ret;
+
+	if (lcd->prepared)
+		return 0;
+
+	ret = regulator_enable(lcd->supply);
+	if (ret < 0)
+		return ret;
+
+	gpiod_set_value_cansleep(lcd->enable_gpio, 1);
+	lcd->prepared = true;
+
+	return 0;
+}
+
+static int lcd_olinuxino_enable(struct drm_panel *panel)
+{
+	struct lcd_olinuxino *lcd = to_lcd_olinuxino(panel);
+
+	if (lcd->enabled)
+		return 0;
+
+	backlight_enable(lcd->backlight);
+
+	lcd->enabled = true;
+
+	return 0;
+}
+
+static int lcd_olinuxino_get_modes(struct drm_panel *panel)
+{
+	struct lcd_olinuxino *lcd = to_lcd_olinuxino(panel);
+	struct drm_connector *connector = lcd->panel.connector;
+	struct lcd_olinuxino_info *lcd_info = &lcd->eeprom.info;
+	struct drm_device *drm = lcd->panel.drm;
+	struct lcd_olinuxino_mode *lcd_mode;
+	struct drm_display_mode *mode;
+	u32 i, num = 0;
+
+	for (i = 0; i < lcd->eeprom.num_modes; i++) {
+		lcd_mode = (struct lcd_olinuxino_mode *)
+			   &lcd->eeprom.reserved[i * sizeof(*lcd_mode)];
+
+		mode = drm_mode_create(drm);
+		if (!mode) {
+			dev_err(drm->dev, "failed to add mode %ux%u@%u\n",
+				lcd_mode->hactive,
+				lcd_mode->vactive,
+				lcd_mode->refresh);
+				continue;
+		}
+
+		mode->clock = lcd_mode->pixelclock;
+		mode->hdisplay = lcd_mode->hactive;
+		mode->hsync_start = lcd_mode->hactive + lcd_mode->hfp;
+		mode->hsync_end = lcd_mode->hactive + lcd_mode->hfp +
+				  lcd_mode->hpw;
+		mode->htotal = lcd_mode->hactive + lcd_mode->hfp +
+			       lcd_mode->hpw + lcd_mode->hbp;
+		mode->vdisplay = lcd_mode->vactive;
+		mode->vsync_start = lcd_mode->vactive + lcd_mode->vfp;
+		mode->vsync_end = lcd_mode->vactive + lcd_mode->vfp +
+				  lcd_mode->vpw;
+		mode->vtotal = lcd_mode->vactive + lcd_mode->vfp +
+			       lcd_mode->vpw + lcd_mode->vbp;
+		mode->vrefresh = lcd_mode->refresh;
+
+		/* Always make the first mode preferred */
+		if (i == 0)
+			mode->type |= DRM_MODE_TYPE_PREFERRED;
+		mode->type |= DRM_MODE_TYPE_DRIVER;
+
+		drm_mode_set_name(mode);
+		drm_mode_probed_add(connector, mode);
+
+		num++;
+	}
+
+	memcpy(connector->display_info.name, lcd_info->name, 32);
+	connector->display_info.width_mm = lcd_info->width_mm;
+	connector->display_info.height_mm = lcd_info->height_mm;
+	connector->display_info.bpc = lcd_info->bpc;
+
+	if (lcd_info->bus_format)
+		drm_display_info_set_bus_formats(&connector->display_info,
+						 &lcd_info->bus_format, 1);
+	connector->display_info.bus_flags = lcd_info->bus_flag;
+
+	return num;
+}
+
+static const struct drm_panel_funcs lcd_olinuxino_funcs = {
+	.disable = lcd_olinuxino_disable,
+	.unprepare = lcd_olinuxino_unprepare,
+	.prepare = lcd_olinuxino_prepare,
+	.enable = lcd_olinuxino_enable,
+	.get_modes = lcd_olinuxino_get_modes,
+};
+
+static int lcd_olinuxino_probe(struct i2c_client *client,
+			       const struct i2c_device_id *id)
+{
+	struct device *dev = &client->dev;
+	struct lcd_olinuxino *lcd;
+	u32 checksum, i;
+	int ret = 0;
+
+	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
+				     I2C_FUNC_SMBUS_READ_I2C_BLOCK))
+		return -ENODEV;
+
+	lcd = devm_kzalloc(dev, sizeof(*lcd), GFP_KERNEL);
+	if (!lcd)
+		return -ENOMEM;
+
+	i2c_set_clientdata(client, lcd);
+	lcd->dev = dev;
+	lcd->client = client;
+
+	mutex_init(&lcd->mutex);
+
+	/* Copy data into buffer */
+	for (i = 0; i < LCD_OLINUXINO_DATA_LEN; i += I2C_SMBUS_BLOCK_MAX) {
+		mutex_lock(&lcd->mutex);
+		ret = i2c_smbus_read_i2c_block_data(client,
+						    i,
+						    I2C_SMBUS_BLOCK_MAX,
+						    (u8 *)&lcd->eeprom + i);
+		mutex_unlock(&lcd->mutex);
+		if (ret < 0) {
+			dev_err(dev, "error reading from device at %02x\n", i);
+			return ret;
+		}
+	}
+
+	/* Check configuration checksum */
+	checksum = ~crc32(~0, (u8 *)&lcd->eeprom, 252);
+	if (checksum != lcd->eeprom.checksum) {
+		dev_err(dev, "configuration checksum does not match!\n");
+		return -EINVAL;
+	}
+
+	/* Check magic header */
+	if (lcd->eeprom.header != LCD_OLINUXINO_HEADER_MAGIC) {
+		dev_err(dev, "magic header does not match\n");
+		return -EINVAL;
+	}
+
+	dev_info(dev, "Detected %s, Rev. %s, Serial: %08x\n",
+		 lcd->eeprom.info.name,
+		 lcd->eeprom.revision,
+		 lcd->eeprom.serial);
+
+	/*
+	 * The eeprom can hold up to 4 modes.
+	 * If the stored value is bigger, overwrite it.
+	 */
+	if (lcd->eeprom.num_modes > 4) {
+		dev_warn(dev, "invalid number of modes, falling back to 4\n");
+		lcd->eeprom.num_modes = 4;
+	}
+
+	lcd->enabled = false;
+	lcd->prepared = false;
+
+	lcd->supply = devm_regulator_get(dev, "power");
+	if (IS_ERR(lcd->supply))
+		return PTR_ERR(lcd->supply);
+
+	lcd->enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(lcd->enable_gpio))
+		return PTR_ERR(lcd->enable_gpio);
+
+	lcd->backlight = devm_of_find_backlight(dev);
+	if (IS_ERR(lcd->backlight))
+		return PTR_ERR(lcd->backlight);
+
+	drm_panel_init(&lcd->panel);
+	lcd->panel.dev = dev;
+	lcd->panel.funcs = &lcd_olinuxino_funcs;
+
+	return drm_panel_add(&lcd->panel);
+}
+
+static int lcd_olinuxino_remove(struct i2c_client *client)
+{
+	struct lcd_olinuxino *panel = i2c_get_clientdata(client);
+
+	drm_panel_remove(&panel->panel);
+
+	lcd_olinuxino_disable(&panel->panel);
+	lcd_olinuxino_unprepare(&panel->panel);
+
+	return 0;
+}
+
+static const struct of_device_id lcd_olinuxino_of_ids[] = {
+	{ .compatible = "olimex,lcd-olinuxino" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, lcd_olinuxino_of_ids);
+
+static struct i2c_driver lcd_olinuxino_driver = {
+	.driver = {
+		.name = "lcd_olinuxino",
+		.of_match_table = lcd_olinuxino_of_ids,
+	},
+	.probe = lcd_olinuxino_probe,
+	.remove = lcd_olinuxino_remove,
+};
+
+module_i2c_driver(lcd_olinuxino_driver);
+
+MODULE_AUTHOR("Stefan Mavrodiev <[e-mail]>");
+MODULE_DESCRIPTION("LCD-OLinuXino driver");
+MODULE_LICENSE("GPL");