drm/bridge: add support for TI TDP158

TDP158 is an AC-coupled DVI / HDMI to TMDS level shifting Redriver.
It supports DVI 1.0, HDMI 1.4b and 2.0b.
It supports 4 TMDS channels, HPD, and a DDC interface.
It supports dual power supply rails (1.1V on VDD, 3.3V on VCC)
for power reduction. Several methods of power management are
implemented to reduce overall power consumption.
It supports fixed receiver EQ gain using I2C or pin strap to
compensate for different lengths input cable or board traces.

Features

- AC-coupled TMDS or DisplayPort dual-mode physical layer input
to HDMI 2.0b TMDS physical layer output supporting up to 6Gbps
data rate, compatible with HDMI 2.0b electrical parameters
- DisplayPort dual-mode standard version 1.1
- Programmable fixed receiver equalizer up to 15.5dB
- Global or independent high speed lane control, pre-emphasis
and transmit swing, and slew rate control
- I2C or pin strap programmable
- Configurable as a DisplayPort redriver through I2C
- Full lane swap on main lanes
- Low power consumption (200 mW at 6Gbps, 8 mW in shutdown)

https://www.ti.com/lit/ds/symlink/tdp158.pdf

On our board, I2C_EN is pulled high.
Thus, this code defines a module_i2c_driver.

The default settings work fine for our use-case.
So this basic driver doesn't need to tweak any I2C registers.

Signed-off-by: Marc Gonzalez <mgonzalez@freebox.fr>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240812-tdp158-v5-2-78684a84ec23@freebox.fr

drivers/gpu/drm/bridge/Kconfig

@@ -368,6 +368,13 @@ config DRM_TI_DLPC3433
 	  It supports up to 720p resolution with 60 and 120 Hz refresh
 	  rates.
 
+config DRM_TI_TDP158
+	tristate "TI TDP158 HDMI/TMDS bridge"
+	depends on OF
+	select DRM_PANEL_BRIDGE
+	help
+	  Texas Instruments TDP158 HDMI/TMDS Bridge driver
+
 config DRM_TI_TFP410
 	tristate "TI TFP410 DVI/HDMI bridge"
 	depends on OF

drivers/gpu/drm/bridge/Makefile

@@ -32,6 +32,7 @@ obj-$(CONFIG_DRM_I2C_ADV7511) += adv7511/
 obj-$(CONFIG_DRM_TI_DLPC3433) += ti-dlpc3433.o
 obj-$(CONFIG_DRM_TI_SN65DSI83) += ti-sn65dsi83.o
 obj-$(CONFIG_DRM_TI_SN65DSI86) += ti-sn65dsi86.o
+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_NWL_MIPI_DSI) += nwl-dsi.o

drivers/gpu/drm/bridge/ti-tdp158.c

@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2024 Freebox SAS
+ */
+#include <drm/drm_bridge.h>
+#include <drm/drm_atomic_helper.h>
+#include <linux/i2c.h>
+
+struct tdp158 {
+	struct drm_bridge bridge;
+	struct drm_bridge *next;
+	struct gpio_desc *enable; // Operation Enable - pin 36
+	struct regulator *vcc; // 3.3V
+	struct regulator *vdd; // 1.1V
+	struct device *dev;
+};
+
+static void tdp158_enable(struct drm_bridge *bridge, struct drm_bridge_state *prev)
+{
+	int err;
+	struct tdp158 *tdp158 = bridge->driver_private;
+
+	err = regulator_enable(tdp158->vcc);
+	if (err)
+		dev_err(tdp158->dev, "failed to enable vcc: %d", err);
+
+	err = regulator_enable(tdp158->vdd);
+	if (err)
+		dev_err(tdp158->dev, "failed to enable vdd: %d", err);
+
+	gpiod_set_value_cansleep(tdp158->enable, 1);
+}
+
+static void tdp158_disable(struct drm_bridge *bridge, struct drm_bridge_state *prev)
+{
+	struct tdp158 *tdp158 = bridge->driver_private;
+
+	gpiod_set_value_cansleep(tdp158->enable, 0);
+	regulator_disable(tdp158->vdd);
+	regulator_disable(tdp158->vcc);
+}
+
+static int tdp158_attach(struct drm_bridge *bridge, enum drm_bridge_attach_flags flags)
+{
+	struct tdp158 *tdp158 = bridge->driver_private;
+
+	return drm_bridge_attach(bridge->encoder, tdp158->next, bridge, flags);
+}
+
+static const struct drm_bridge_funcs tdp158_bridge_funcs = {
+	.attach = tdp158_attach,
+	.atomic_enable = tdp158_enable,
+	.atomic_disable = tdp158_disable,
+	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
+	.atomic_reset = drm_atomic_helper_bridge_reset,
+};
+
+static int tdp158_probe(struct i2c_client *client)
+{
+	struct tdp158 *tdp158;
+	struct device *dev = &client->dev;
+
+	tdp158 = devm_kzalloc(dev, sizeof(*tdp158), GFP_KERNEL);
+	if (!tdp158)
+		return -ENOMEM;
+
+	tdp158->next = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
+	if (IS_ERR(tdp158->next))
+		return dev_err_probe(dev, PTR_ERR(tdp158->next), "missing bridge");
+
+	tdp158->vcc = devm_regulator_get(dev, "vcc");
+	if (IS_ERR(tdp158->vcc))
+		return dev_err_probe(dev, PTR_ERR(tdp158->vcc), "vcc");
+
+	tdp158->vdd = devm_regulator_get(dev, "vdd");
+	if (IS_ERR(tdp158->vdd))
+		return dev_err_probe(dev, PTR_ERR(tdp158->vdd), "vdd");
+
+	tdp158->enable = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_LOW);
+	if (IS_ERR(tdp158->enable))
+		return dev_err_probe(dev, PTR_ERR(tdp158->enable), "enable");
+
+	tdp158->bridge.of_node = dev->of_node;
+	tdp158->bridge.funcs = &tdp158_bridge_funcs;
+	tdp158->bridge.driver_private = tdp158;
+	tdp158->dev = dev;
+
+	return devm_drm_bridge_add(dev, &tdp158->bridge);
+}
+
+static const struct of_device_id tdp158_match_table[] = {
+	{ .compatible = "ti,tdp158" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, tdp158_match_table);
+
+static struct i2c_driver tdp158_driver = {
+	.probe = tdp158_probe,
+	.driver = {
+		.name = "tdp158",
+		.of_match_table = tdp158_match_table,
+	},
+};
+module_i2c_driver(tdp158_driver);
+
+MODULE_DESCRIPTION("TI TDP158 driver");
+MODULE_LICENSE("GPL");