[v7,2/2] drm/bridge: hx8837: add a Himax HX8837 display controller driver

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index e4110d6ca7b3c..9d753f55bcc05 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -48,6 +48,18 @@  config DRM_DISPLAY_CONNECTOR
 	  on ARM-based platforms. Saying Y here when this driver is not needed
 	  will not cause any issue.
 
+config DRM_HIMAX_HX8837
+	tristate "HiMax HX8837 OLPC Display Controller"
+	depends on OF
+	depends on OLPC || ARCH_MMP || COMPILE_TEST
+	select DRM_KMS_HELPER
+	select BACKLIGHT_CLASS_DEVICE
+	help
+	  Enable support for HiMax HX8837 Display Controller as found in the
+	  OLPC XO laptops.
+
+	  If your laptop doesn't have green ears, say "N"
+
 config DRM_LONTIUM_LT9611
 	tristate "Lontium LT9611 DSI/HDMI bridge"
 	select SND_SOC_HDMI_CODEC if SND_SOC
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 86e7acc76f8d6..1e27939d69d09 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -2,6 +2,7 @@ 
 obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
 obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
 obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
+obj-$(CONFIG_DRM_HIMAX_HX8837) += himax-hx8837.o
 obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
 obj-$(CONFIG_DRM_LONTIUM_LT9611UXC) += lontium-lt9611uxc.o
 obj-$(CONFIG_DRM_LVDS_CODEC) += lvds-codec.o
diff --git a/drivers/gpu/drm/bridge/himax-hx8837.c b/drivers/gpu/drm/bridge/himax-hx8837.c
new file mode 100644
index 0000000000000..b97b71ba3f32e
--- /dev/null
+++ b/drivers/gpu/drm/bridge/himax-hx8837.c
@@ -0,0 +1,328 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HiMax HX8837 Display Controller Driver
+ *
+ * Datasheet: http://wiki.laptop.org/images/0/09/DCON_datasheet_HX8837-A.pdf
+ *
+ * Copyright (C) 2020 Lubomir Rintel
+ */
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_of.h>
+#include <drm/drm_panel.h>
+#include <drm/drm_probe_helper.h>
+
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#define bridge_to_hx8837_priv(x) \
+	container_of(x, struct hx8837_priv, bridge)
+
+/* DCON registers */
+enum {
+	DCON_REG_ID		= 0x00,
+	DCON_REG_MODE		= 0x01,
+	DCON_REG_HRES		= 0x02,
+	DCON_REG_HTOTAL		= 0x03,
+	DCON_REG_HSYNC_WIDTH	= 0x04,
+	DCON_REG_VRES		= 0x05,
+	DCON_REG_VTOTAL		= 0x06,
+	DCON_REG_VSYNC_WIDTH	= 0x07,
+	DCON_REG_TIMEOUT	= 0x08,
+	DCON_REG_SCAN_INT	= 0x09,
+	DCON_REG_BRIGHT		= 0x0a,
+	DCON_REG_MEM_OPT_A	= 0x41,
+	DCON_REG_MEM_OPT_B	= 0x42,
+};
+
+/* DCON_REG_MODE */
+enum {
+	MODE_PASSTHRU		= BIT(0),
+	MODE_SLEEP		= BIT(1),
+	MODE_SLEEP_AUTO		= BIT(2),
+	MODE_BL_ENABLE		= BIT(3),
+	MODE_BLANK		= BIT(4),
+	MODE_CSWIZZLE		= BIT(5),
+	MODE_COL_AA		= BIT(6),
+	MODE_MONO_LUMA		= BIT(7),
+	MODE_SCAN_INT		= BIT(8),
+	MODE_CLOCKDIV		= BIT(9),
+	MODE_DEBUG		= BIT(14),
+	MODE_SELFTEST		= BIT(15),
+};
+
+/* DCON_REG_BRIGHT */
+enum {
+	BRIGHT_MASK		= GENMASK(7, 0),
+};
+
+struct hx8837_priv {
+	struct device *dev;
+	struct regmap *regmap;
+	struct gpio_desc *load_gpio;
+
+	struct drm_bridge *panel_bridge;
+	struct drm_bridge bridge;
+};
+
+static int hx8837_bridge_attach(struct drm_bridge *bridge,
+				enum drm_bridge_attach_flags flags)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+
+	return drm_bridge_attach(bridge->encoder, priv->panel_bridge,
+				 bridge, flags);
+}
+
+static enum drm_mode_status hx8837_bridge_mode_valid(
+				struct drm_bridge *bridge,
+				const struct drm_display_info *info,
+				const struct drm_display_mode *mode)
+{
+	if (mode->hdisplay > 0xffff)
+		return MODE_BAD_HVALUE;
+	if (mode->htotal > 0xffff)
+		return MODE_BAD_HVALUE;
+	if (mode->hsync_start - mode->hdisplay > 0xff)
+		return MODE_HBLANK_WIDE;
+	if (mode->hsync_end - mode->hsync_start > 0xff)
+		return MODE_HSYNC_WIDE;
+	if (mode->vdisplay > 0xffff)
+		return MODE_BAD_VVALUE;
+	if (mode->vtotal > 0xffff)
+		return MODE_BAD_VVALUE;
+	if (mode->vsync_start - mode->vdisplay > 0xff)
+		return MODE_VBLANK_WIDE;
+	if (mode->vsync_end - mode->vsync_start > 0xff)
+		return MODE_VSYNC_WIDE;
+
+	return MODE_OK;
+}
+
+static void hx8837_bridge_disable(struct drm_bridge *bridge)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+	int ret;
+
+	ret = gpiod_direction_output(priv->load_gpio, 0);
+	if (ret)
+		dev_err(priv->dev, "error disabling the dcon load: %d\n", ret);
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP);
+	if (ret)
+		dev_err(priv->dev, "error disabling the dcon: %d\n", ret);
+}
+
+static void hx8837_bridge_enable(struct drm_bridge *bridge)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+	int ret;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_PASSTHRU |
+					       MODE_SLEEP |
+					       MODE_SLEEP_AUTO |
+					       MODE_BLANK |
+					       MODE_SCAN_INT |
+					       MODE_CLOCKDIV |
+					       MODE_DEBUG |
+					       MODE_SELFTEST,
+					       MODE_PASSTHRU);
+	if (ret)
+		dev_err(priv->dev, "error enabling the dcon: %d\n", ret);
+
+	ret = gpiod_direction_output(priv->load_gpio, 1);
+	if (ret)
+		dev_err(priv->dev, "error enabling the dcon load: %d\n", ret);
+}
+
+static void hx8837_bridge_mode_set(struct drm_bridge *bridge,
+			   const struct drm_display_mode *mode,
+			   const struct drm_display_mode *adjusted_mode)
+{
+	struct hx8837_priv *priv = bridge_to_hx8837_priv(bridge);
+
+	regmap_write(priv->regmap, DCON_REG_HRES, mode->hdisplay);
+	regmap_write(priv->regmap, DCON_REG_HTOTAL, mode->htotal);
+	regmap_write(priv->regmap, DCON_REG_HSYNC_WIDTH,
+			(mode->hsync_start - mode->hdisplay) << 8 |
+			(mode->hsync_end - mode->hsync_start));
+	regmap_write(priv->regmap, DCON_REG_VRES, mode->vdisplay);
+	regmap_write(priv->regmap, DCON_REG_VTOTAL, mode->vtotal);
+	regmap_write(priv->regmap, DCON_REG_VSYNC_WIDTH,
+			(mode->vsync_start - mode->vdisplay) << 8 |
+			(mode->vsync_end - mode->vsync_start));
+}
+
+static const struct drm_bridge_funcs hx8837_bridge_funcs = {
+	.attach = hx8837_bridge_attach,
+	.mode_valid = hx8837_bridge_mode_valid,
+	.disable = hx8837_bridge_disable,
+	.enable = hx8837_bridge_enable,
+	.mode_set = hx8837_bridge_mode_set,
+};
+
+static int hx8837_bl_update_status(struct backlight_device *bl)
+{
+	struct hx8837_priv *priv = bl_get_data(bl);
+	unsigned int val;
+	int ret;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_BRIGHT,
+					       BRIGHT_MASK,
+					       backlight_get_brightness(bl));
+	if (ret) {
+		dev_err(&bl->dev, "error setting the backlight: %d\n", ret);
+		return ret;
+	}
+
+	if (backlight_get_brightness(bl))
+		val = MODE_CSWIZZLE | MODE_COL_AA;
+	else
+		val = MODE_MONO_LUMA;
+
+	ret = regmap_update_bits(priv->regmap, DCON_REG_MODE,
+					       MODE_CSWIZZLE |
+					       MODE_COL_AA |
+					       MODE_MONO_LUMA,
+					       val);
+	if (ret) {
+		dev_err(&bl->dev, "error setting color mode: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct backlight_ops hx8837_bl_ops = {
+	.update_status = hx8837_bl_update_status,
+};
+
+static const struct regmap_config hx8837_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+	.max_register = 0x4c,
+	.val_format_endian = REGMAP_ENDIAN_LITTLE,
+};
+
+static int hx8837_probe(struct i2c_client *client,
+			const struct i2c_device_id *id)
+{
+	struct backlight_properties bl_props = {
+		.type = BACKLIGHT_RAW,
+		.max_brightness = BRIGHT_MASK,
+	};
+	struct device *dev = &client->dev;
+	struct backlight_device *bl;
+	struct hx8837_priv *priv;
+	struct drm_panel *panel;
+	unsigned int val;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, priv);
+	priv->dev = dev;
+
+	priv->load_gpio = devm_gpiod_get(dev, "load", GPIOD_ASIS);
+	if (IS_ERR(priv->load_gpio))
+		return PTR_ERR(priv->load_gpio);
+
+	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1, &panel, NULL);
+	if (ret)
+		return ret;
+
+	if (panel->backlight) {
+		dev_err(dev, "the panel already has a backlight controller\n");
+		return -ENODEV;
+	}
+
+	priv->panel_bridge = devm_drm_panel_bridge_add(dev, panel);
+	if (IS_ERR(priv->panel_bridge))
+		return PTR_ERR(priv->panel_bridge);
+
+	priv->regmap = devm_regmap_init_i2c(client, &hx8837_regmap_config);
+	if (IS_ERR(priv->regmap)) {
+		dev_err(dev, "regmap_init_i2c failed\n");
+		return PTR_ERR(priv->regmap);
+	}
+
+	ret = regmap_read(priv->regmap, DCON_REG_ID, &val);
+	if (ret < 0) {
+		dev_err(dev, "error reading the model id: %d\n", ret);
+		return ret;
+	}
+	if ((val & 0xff00) != 0xdc00) {
+		dev_err(dev, "the device is not a hx8837\n");
+		return -ENODEV;
+	}
+
+	ret = regmap_read(priv->regmap, DCON_REG_BRIGHT, &val);
+	if (ret < 0) {
+		dev_err(&bl->dev, "error getting the backlight: %d\n", ret);
+		return ret;
+	}
+	bl_props.brightness = val & 0xf;
+
+	bl = devm_backlight_device_register(dev, dev_name(dev), dev, priv,
+					    &hx8837_bl_ops, &bl_props);
+	if (IS_ERR(bl)) {
+		dev_err(dev, "failed to register backlight\n");
+		return PTR_ERR(bl);
+	}
+
+	panel->backlight = bl;
+
+	INIT_LIST_HEAD(&priv->bridge.list);
+	priv->bridge.funcs = &hx8837_bridge_funcs;
+	priv->bridge.of_node = dev->of_node;
+	drm_bridge_add(&priv->bridge);
+
+	return 0;
+}
+
+static int hx8837_remove(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct hx8837_priv *priv = dev_get_drvdata(dev);
+
+	drm_bridge_remove(&priv->bridge);
+
+	return 0;
+}
+
+static const struct of_device_id hx8837_dt_ids[] = {
+	{ .compatible = "himax,hx8837", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, hx8837_dt_ids);
+
+static const struct i2c_device_id hx8837_ids[] = {
+	{ "hx8837", 0 },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, hx8837_ids);
+
+static struct i2c_driver hx8837_driver = {
+	.probe = hx8837_probe,
+	.remove = hx8837_remove,
+	.driver = {
+		.name = "hx8837",
+		.of_match_table = of_match_ptr(hx8837_dt_ids),
+	},
+	.id_table = hx8837_ids,
+};
+
+module_i2c_driver(hx8837_driver);
+
+MODULE_AUTHOR("Lubomir Rintel <lkundrak@v3.sk>");
+MODULE_DESCRIPTION("HiMax HX8837 Display Controller Driver");
+MODULE_LICENSE("GPL");