drm: bridge: Add waveshare DSI2DPI unit driver

Waveshare touchscreen consists of a DPI panel and a driver board.
The waveshare driver board consists of ICN6211 and a MCU to
convert DSI to DPI and control the backlight.
This driver treats the MCU and ICN6211 board as a whole unit.
It can support all resolution waveshare DSI2DPI based panel,
the timing table should come from 'panel-dpi' panel in the device tree.

Signed-off-by: Joseph Guo <[e-mail]>
Suggested-by: Liu Ying <[e-mail]>
Reviewed-by: Neil Armstrong <[e-mail]>
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/bridge/Kconfig

···
 	  Texas Instruments TPD12S015 HDMI level shifter and ESD protection
 	  driver.
 
+config DRM_WAVESHARE_BRIDGE
+	tristate "Waveshare DSI bridge"
+	depends on OF
+	depends on BACKLIGHT_CLASS_DEVICE
+	select DRM_PANEL_BRIDGE
+	select DRM_KMS_HELPER
+	select DRM_MIPI_DSI
+	select REGMAP_I2C
+	help
+	  Driver for waveshare DSI to DPI bridge board.
+	  Please say Y if you have such hardware
+
 source "drivers/gpu/drm/bridge/analogix/Kconfig"
 
 source "drivers/gpu/drm/bridge/adv7511/Kconfig"

drivers/gpu/drm/bridge/Makefile

···
 obj-$(CONFIG_DRM_TI_TDP158) += ti-tdp158.o
 obj-$(CONFIG_DRM_TI_TFP410) += ti-tfp410.o
 obj-$(CONFIG_DRM_TI_TPD12S015) += ti-tpd12s015.o
+obj-$(CONFIG_DRM_WAVESHARE_BRIDGE) += waveshare-dsi.o
 obj-$(CONFIG_DRM_NWL_MIPI_DSI) += nwl-dsi.o
 obj-$(CONFIG_DRM_ITE_IT66121) += ite-it66121.o
 

drivers/gpu/drm/bridge/waveshare-dsi.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2025 NXP
+ * Based on panel-raspberrypi-touchscreen by Broadcom
+ */
+
+#include <linux/backlight.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_graph.h>
+#include <linux/regmap.h>
+
+#include <drm/drm_bridge.h>
+#include <drm/drm_mipi_dsi.h>
+#include <drm/drm_of.h>
+#include <drm/drm_panel.h>
+
+struct ws_bridge {
+	struct drm_bridge bridge;
+	struct drm_bridge *next_bridge;
+	struct backlight_device *backlight;
+	struct device *dev;
+	struct regmap *reg_map;
+};
+
+static const struct regmap_config ws_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = 0xff,
+};
+
+static struct ws_bridge *bridge_to_ws_bridge(struct drm_bridge *bridge)
+{
+	return container_of(bridge, struct ws_bridge, bridge);
+}
+
+static int ws_bridge_attach_dsi(struct ws_bridge *ws)
+{
+	const struct mipi_dsi_device_info info = {
+		.type = "ws-bridge",
+		.channel = 0,
+		.node = NULL,
+	};
+	struct device_node *dsi_host_node;
+	struct device *dev = ws->dev;
+	struct mipi_dsi_device *dsi;
+	struct mipi_dsi_host *host;
+	int ret;
+
+	dsi_host_node = of_graph_get_remote_node(dev->of_node, 0, 0);
+	if (!dsi_host_node) {
+		dev_err(dev, "Failed to get remote port\n");
+		return -ENODEV;
+	}
+	host = of_find_mipi_dsi_host_by_node(dsi_host_node);
+	of_node_put(dsi_host_node);
+	if (!host)
+		return dev_err_probe(dev, -EPROBE_DEFER, "Failed to find dsi_host\n");
+
+	dsi = devm_mipi_dsi_device_register_full(dev, host, &info);
+	if (IS_ERR(dsi))
+		return dev_err_probe(dev, PTR_ERR(dsi), "Failed to create dsi device\n");
+
+	dsi->mode_flags = MIPI_DSI_MODE_VIDEO_HSE | MIPI_DSI_MODE_VIDEO |
+			  MIPI_DSI_CLOCK_NON_CONTINUOUS;
+	dsi->format = MIPI_DSI_FMT_RGB888;
+	dsi->lanes = 2;
+
+	ret = devm_mipi_dsi_attach(dev, dsi);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to attach dsi to host\n");
+
+	return 0;
+}
+
+static int ws_bridge_bridge_attach(struct drm_bridge *bridge,
+				   struct drm_encoder *encoder,
+				   enum drm_bridge_attach_flags flags)
+{
+	struct ws_bridge *ws = bridge_to_ws_bridge(bridge);
+	int ret;
+
+	ret = ws_bridge_attach_dsi(ws);
+	if (ret)
+		return ret;
+
+	return drm_bridge_attach(encoder, ws->next_bridge,
+				 &ws->bridge, flags);
+}
+
+static void ws_bridge_bridge_enable(struct drm_bridge *bridge)
+{
+	struct ws_bridge *ws = bridge_to_ws_bridge(bridge);
+
+	regmap_write(ws->reg_map, 0xad, 0x01);
+	backlight_enable(ws->backlight);
+}
+
+static void ws_bridge_bridge_disable(struct drm_bridge *bridge)
+{
+	struct ws_bridge *ws = bridge_to_ws_bridge(bridge);
+
+	backlight_disable(ws->backlight);
+	regmap_write(ws->reg_map, 0xad, 0x00);
+}
+
+static const struct drm_bridge_funcs ws_bridge_bridge_funcs = {
+	.enable = ws_bridge_bridge_enable,
+	.disable = ws_bridge_bridge_disable,
+	.attach = ws_bridge_bridge_attach,
+};
+
+static int ws_bridge_bl_update_status(struct backlight_device *bl)
+{
+	struct ws_bridge *ws = bl_get_data(bl);
+
+	regmap_write(ws->reg_map, 0xab, 0xff - backlight_get_brightness(bl));
+	regmap_write(ws->reg_map, 0xaa, 0x01);
+
+	return 0;
+}
+
+static const struct backlight_ops ws_bridge_bl_ops = {
+	.update_status = ws_bridge_bl_update_status,
+};
+
+static struct backlight_device *ws_bridge_create_backlight(struct ws_bridge *ws)
+{
+	const struct backlight_properties props = {
+		.type = BACKLIGHT_RAW,
+		.brightness = 255,
+		.max_brightness = 255,
+	};
+	struct device *dev = ws->dev;
+
+	return devm_backlight_device_register(dev, dev_name(dev), dev, ws,
+					      &ws_bridge_bl_ops, &props);
+}
+
+static int ws_bridge_probe(struct i2c_client *i2c)
+{
+	struct device *dev = &i2c->dev;
+	struct drm_panel *panel;
+	struct ws_bridge *ws;
+	int ret;
+
+	ws = devm_drm_bridge_alloc(dev, struct ws_bridge, bridge, &ws_bridge_bridge_funcs);
+	if (!ws)
+		return -ENOMEM;
+
+	ws->dev = dev;
+
+	ws->reg_map = devm_regmap_init_i2c(i2c, &ws_regmap_config);
+	if (IS_ERR(ws->reg_map))
+		return dev_err_probe(dev, PTR_ERR(ws->reg_map), "Failed to allocate regmap\n");
+
+	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, -1, &panel, NULL);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to find remote panel\n");
+
+	ws->next_bridge = devm_drm_panel_bridge_add(dev, panel);
+	if (IS_ERR(ws->next_bridge))
+		return PTR_ERR(ws->next_bridge);
+
+	ws->backlight = ws_bridge_create_backlight(ws);
+	if (IS_ERR(ws->backlight)) {
+		ret = PTR_ERR(ws->backlight);
+		dev_err(dev, "Failed to create backlight: %d\n", ret);
+		return ret;
+	}
+
+	regmap_write(ws->reg_map, 0xc0, 0x01);
+	regmap_write(ws->reg_map, 0xc2, 0x01);
+	regmap_write(ws->reg_map, 0xac, 0x01);
+
+	ws->bridge.type = DRM_MODE_CONNECTOR_DPI;
+	ws->bridge.of_node = dev->of_node;
+	devm_drm_bridge_add(dev, &ws->bridge);
+
+	return 0;
+}
+
+static const struct of_device_id ws_bridge_of_ids[] = {
+	{.compatible = "waveshare,dsi2dpi",},
+	{ }
+};
+
+MODULE_DEVICE_TABLE(of, ws_bridge_of_ids);
+
+static struct i2c_driver ws_bridge_driver = {
+	.driver = {
+		.name = "ws_dsi2dpi",
+		.of_match_table = ws_bridge_of_ids,
+	},
+	.probe = ws_bridge_probe,
+};
+module_i2c_driver(ws_bridge_driver);
+
+MODULE_AUTHOR("Joseph Guo <[e-mail]>");
+MODULE_DESCRIPTION("Waveshare DSI2DPI bridge driver");
+MODULE_LICENSE("GPL");