drm: panels: Add LVDS panel driver

This driver supports LVDS panels that don't require device-specific
handling of power supplies or control signals. It implements automatic
backlight handling if the panel is attached to a backlight controller.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

drivers/gpu/drm/panel/Kconfig

@@ -7,6 +7,16 @@ config DRM_PANEL
 menu "Display Panels"
 	depends on DRM && DRM_PANEL
 
+config DRM_PANEL_LVDS
+	tristate "Generic LVDS panel driver"
+	depends on OF
+	depends on BACKLIGHT_CLASS_DEVICE
+	select VIDEOMODE_HELPERS
+	help
+	  This driver supports LVDS panels that don't require device-specific
+	  handling of power supplies or control signals. It implements automatic
+	  backlight handling if the panel is attached to a backlight controller.
+
 config DRM_PANEL_SIMPLE
 	tristate "support for simple panels"
 	depends on OF

drivers/gpu/drm/panel/Makefile

+obj-$(CONFIG_DRM_PANEL_LVDS) += panel-lvds.o
 obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
 obj-$(CONFIG_DRM_PANEL_JDI_LT070ME05000) += panel-jdi-lt070me05000.o
 obj-$(CONFIG_DRM_PANEL_LG_LG4573) += panel-lg-lg4573.o

drivers/gpu/drm/panel/panel-lvds.c

+/*
+ * rcar_du_crtc.c  --  R-Car Display Unit CRTCs
+ *
+ * Copyright (C) 2016 Laurent Pinchart
+ * Copyright (C) 2016 Renesas Electronics Corporation
+ *
+ * Contact: Laurent Pinchart (laurent.pinchart@ideasonboard.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/backlight.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include <drm/drmP.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_panel.h>
+
+#include <video/display_timing.h>
+#include <video/of_display_timing.h>
+#include <video/videomode.h>
+
+struct panel_lvds {
+	struct drm_panel panel;
+	struct device *dev;
+
+	const char *label;
+	unsigned int width;
+	unsigned int height;
+	struct videomode video_mode;
+	unsigned int bus_format;
+	bool data_mirror;
+
+	struct backlight_device *backlight;
+
+	struct gpio_desc *enable_gpio;
+	struct gpio_desc *reset_gpio;
+};
+
+static inline struct panel_lvds *to_panel_lvds(struct drm_panel *panel)
+{
+	return container_of(panel, struct panel_lvds, panel);
+}
+
+static int panel_lvds_disable(struct drm_panel *panel)
+{
+	struct panel_lvds *lvds = to_panel_lvds(panel);
+
+	if (lvds->backlight) {
+		lvds->backlight->props.power = FB_BLANK_POWERDOWN;
+		lvds->backlight->props.state |= BL_CORE_FBBLANK;
+		backlight_update_status(lvds->backlight);
+	}
+
+	return 0;
+}
+
+static int panel_lvds_unprepare(struct drm_panel *panel)
+{
+	struct panel_lvds *lvds = to_panel_lvds(panel);
+
+	if (lvds->enable_gpio)
+		gpiod_set_value_cansleep(lvds->enable_gpio, 0);
+
+	return 0;
+}
+
+static int panel_lvds_prepare(struct drm_panel *panel)
+{
+	struct panel_lvds *lvds = to_panel_lvds(panel);
+
+	if (lvds->enable_gpio)
+		gpiod_set_value_cansleep(lvds->enable_gpio, 1);
+
+	return 0;
+}
+
+static int panel_lvds_enable(struct drm_panel *panel)
+{
+	struct panel_lvds *lvds = to_panel_lvds(panel);
+
+	if (lvds->backlight) {
+		lvds->backlight->props.state &= ~BL_CORE_FBBLANK;
+		lvds->backlight->props.power = FB_BLANK_UNBLANK;
+		backlight_update_status(lvds->backlight);
+	}
+
+	return 0;
+}
+
+static int panel_lvds_get_modes(struct drm_panel *panel)
+{
+	struct panel_lvds *lvds = to_panel_lvds(panel);
+	struct drm_connector *connector = lvds->panel.connector;
+	struct drm_display_mode *mode;
+
+	mode = drm_mode_create(lvds->panel.drm);
+	if (!mode)
+		return 0;
+
+	drm_display_mode_from_videomode(&lvds->video_mode, mode);
+	mode->type |= DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+	drm_mode_probed_add(connector, mode);
+
+	connector->display_info.width_mm = lvds->width;
+	connector->display_info.height_mm = lvds->height;
+	drm_display_info_set_bus_formats(&connector->display_info,
+					 &lvds->bus_format, 1);
+	connector->display_info.bus_flags = lvds->data_mirror
+					  ? DRM_BUS_FLAG_DATA_LSB_TO_MSB
+					  : DRM_BUS_FLAG_DATA_MSB_TO_LSB;
+
+	return 1;
+}
+
+static const struct drm_panel_funcs panel_lvds_funcs = {
+	.disable = panel_lvds_disable,
+	.unprepare = panel_lvds_unprepare,
+	.prepare = panel_lvds_prepare,
+	.enable = panel_lvds_enable,
+	.get_modes = panel_lvds_get_modes,
+};
+
+static int panel_lvds_parse_dt(struct panel_lvds *lvds)
+{
+	struct device_node *np = lvds->dev->of_node;
+	struct display_timing timing;
+	const char *mapping;
+	int ret;
+
+	ret = of_get_display_timing(np, "panel-timing", &timing);
+	if (ret < 0)
+		return ret;
+
+	videomode_from_timing(&timing, &lvds->video_mode);
+
+	ret = of_property_read_u32(np, "width-mm", &lvds->width);
+	if (ret < 0) {
+		dev_err(lvds->dev, "%s: invalid or missing %s DT property\n",
+			of_node_full_name(np), "width-mm");
+		return -ENODEV;
+	}
+	ret = of_property_read_u32(np, "height-mm", &lvds->height);
+	if (ret < 0) {
+		dev_err(lvds->dev, "%s: invalid or missing %s DT property\n",
+			of_node_full_name(np), "height-mm");
+		return -ENODEV;
+	}
+
+	of_property_read_string(np, "label", &lvds->label);
+
+	ret = of_property_read_string(np, "data-mapping", &mapping);
+	if (ret < 0) {
+		dev_err(lvds->dev, "%s: invalid or missing %s DT property\n",
+			of_node_full_name(np), "data-mapping");
+		return -ENODEV;
+	}
+
+	if (!strcmp(mapping, "jeida-18")) {
+		lvds->bus_format = MEDIA_BUS_FMT_RGB666_1X7X3_SPWG;
+	} else if (!strcmp(mapping, "jeida-24")) {
+		lvds->bus_format = MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA;
+	} else if (!strcmp(mapping, "vesa-24")) {
+		lvds->bus_format = MEDIA_BUS_FMT_RGB888_1X7X4_SPWG;
+	} else {
+		dev_err(lvds->dev, "%s: invalid or missing %s DT property\n",
+			of_node_full_name(np), "data-mapping");
+		return -EINVAL;
+	}
+
+	lvds->data_mirror = of_property_read_bool(np, "data-mirror");
+
+	return 0;
+}
+
+static int panel_lvds_probe(struct platform_device *pdev)
+{
+	struct panel_lvds *lvds;
+	struct device_node *np;
+	int ret;
+
+	lvds = devm_kzalloc(&pdev->dev, sizeof(*lvds), GFP_KERNEL);
+	if (!lvds)
+		return -ENOMEM;
+
+	lvds->dev = &pdev->dev;
+
+	ret = panel_lvds_parse_dt(lvds);
+	if (ret < 0)
+		return ret;
+
+	/* Get GPIOs and backlight controller. */
+	lvds->enable_gpio = devm_gpiod_get_optional(lvds->dev, "enable",
+						     GPIOD_OUT_LOW);
+	if (IS_ERR(lvds->enable_gpio)) {
+		ret = PTR_ERR(lvds->enable_gpio);
+		dev_err(lvds->dev, "failed to request %s GPIO: %d\n",
+			"enable", ret);
+		return ret;
+	}
+
+	lvds->reset_gpio = devm_gpiod_get_optional(lvds->dev, "reset",
+						     GPIOD_OUT_HIGH);
+	if (IS_ERR(lvds->reset_gpio)) {
+		ret = PTR_ERR(lvds->reset_gpio);
+		dev_err(lvds->dev, "failed to request %s GPIO: %d\n",
+			"reset", ret);
+		return ret;
+	}
+
+	np = of_parse_phandle(lvds->dev->of_node, "backlight", 0);
+	if (np) {
+		lvds->backlight = of_find_backlight_by_node(np);
+		of_node_put(np);
+
+		if (!lvds->backlight)
+			return -EPROBE_DEFER;
+	}
+
+	/*
+	 * TODO: Handle all power supplies specified in the DT node in a generic
+	 * way for panels that don't care about power supply ordering. LVDS
+	 * panels that require a specific power sequence will need a dedicated
+	 * driver.
+	 */
+
+	/* Register the panel. */
+	drm_panel_init(&lvds->panel);
+	lvds->panel.dev = lvds->dev;
+	lvds->panel.funcs = &panel_lvds_funcs;
+
+	ret = drm_panel_add(&lvds->panel);
+	if (ret < 0)
+		goto error;
+
+	dev_set_drvdata(lvds->dev, lvds);
+	return 0;
+
+error:
+	put_device(&lvds->backlight->dev);
+	return ret;
+}
+
+static int panel_lvds_remove(struct platform_device *pdev)
+{
+	struct panel_lvds *lvds = dev_get_drvdata(&pdev->dev);
+
+	drm_panel_detach(&lvds->panel);
+	drm_panel_remove(&lvds->panel);
+
+	panel_lvds_disable(&lvds->panel);
+
+	if (lvds->backlight)
+		put_device(&lvds->backlight->dev);
+
+	return 0;
+}
+
+static const struct of_device_id panel_lvds_of_table[] = {
+	{ .compatible = "panel-lvds", },
+	{ /* Sentinel */ },
+};
+
+MODULE_DEVICE_TABLE(of, panel_lvds_of_table);
+
+static struct platform_driver panel_lvds_driver = {
+	.probe		= panel_lvds_probe,
+	.remove		= panel_lvds_remove,
+	.driver		= {
+		.name	= "panel-lvds",
+		.of_match_table = panel_lvds_of_table,
+	},
+};
+
+module_platform_driver(panel_lvds_driver);
+
+MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
+MODULE_DESCRIPTION("LVDS Panel Driver");
+MODULE_LICENSE("GPL");