On Tue, Aug 12, 2025 at 04:51:35PM +0200, Mike Looijmans wrote:
> The tmds181 and sn65dp159 are "retimers" and hence can be considered
> HDMI-to-HDMI bridges. Typical usage is to convert the output of an
> FPGA into a valid HDMI signal, and it will typically be inserted
> between an encoder and hdmi-connector.
>
> Signed-off-by: Mike Looijmans <mike.looijm...@topic.nl>
> ---
>
> drivers/gpu/drm/bridge/Kconfig | 11 +
> drivers/gpu/drm/bridge/Makefile | 1 +
> drivers/gpu/drm/bridge/ti-tmds181.c | 512 ++++++++++++++++++++++++++++
> 3 files changed, 524 insertions(+)
> create mode 100644 drivers/gpu/drm/bridge/ti-tmds181.c
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index b9e0ca85226a..753177fc9b50 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -430,6 +430,17 @@ config DRM_TI_SN65DSI86
> help
> Texas Instruments SN65DSI86 DSI to eDP Bridge driver
>
> +config DRM_TI_TMDS181
> + tristate "TI TMDS181 and SN65DP159 HDMI retimer bridge driver"
> + depends on OF
> + select DRM_KMS_HELPER
> + select REGMAP_I2C
> + help
> + Enable this to support the TI TMDS181 and SN65DP159 HDMI retimers.
> + The SN65DP159 provides output into a cable (source) whereas the
> + TMDS181 is meant to forward a cable signal into a PCB (sink). Either
> + can be set up as source or sink though.
> +
> config DRM_TI_TPD12S015
> tristate "TI TPD12S015 HDMI level shifter and ESD protection"
> depends on OF
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 245e8a27e3fc..f4b5089e903c 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -39,6 +39,7 @@ 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-$(CONFIG_DRM_TI_TMDS181) += ti-tmds181.o
> obj-$(CONFIG_DRM_TI_TPD12S015) += ti-tpd12s015.o
> obj-$(CONFIG_DRM_NWL_MIPI_DSI) += nwl-dsi.o
> obj-$(CONFIG_DRM_ITE_IT66121) += ite-it66121.o
> diff --git a/drivers/gpu/drm/bridge/ti-tmds181.c
> b/drivers/gpu/drm/bridge/ti-tmds181.c
> new file mode 100644
> index 000000000000..6fbbc13ddc10
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/ti-tmds181.c
> @@ -0,0 +1,512 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * TI tmds181 and sn65dp159 HDMI redriver and retimer chips
> + *
> + * Copyright (C) 2018 - 2025 Topic Embedded Products <www.topic.nl>
> + *
> + * based on code
> + * Copyright (C) 2007 Hans Verkuil
> + * Copyright (C) 2016, 2017 Leon Woestenberg <l...@sidebranch.com>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/i2c.h>
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +#include <linux/regmap.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/delay.h>
> +
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_bridge.h>
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_probe_helper.h>
> +
> +MODULE_DESCRIPTION("I2C device driver for DP159 and TMDS181
> redriver/retimer");
> +MODULE_AUTHOR("Mike Looijmans");
> +MODULE_LICENSE("GPL");
> +
> +#define TMDS181_REG_ID 0
> +#define TMDS181_REG_REV 0x8
> +#define TMDS181_REG_CTRL9 0x9
> +/* Registers A and B have a volatile bit, but we don't use it, so cache is
> ok */
> +#define TMDS181_REG_CTRLA 0xA
> +#define TMDS181_REG_CTRLB 0xB
> +#define TMDS181_REG_CTRLC 0xC
> +#define TMDS181_REG_EQUALIZER 0xD
> +#define TMDS181_REG_EYESCAN 0xE
Usually it's recommended to use lowercase hex.
> +
> +enum tmds181_chip {
> + tmds181,
> + dp159,
> +};
> +
> +struct tmds181_data {
> + struct i2c_client *client;
> + struct regmap *regmap;
> + struct drm_bridge *next_bridge;
> + struct drm_bridge bridge;
> + enum tmds181_chip chip;
> +};
> +
[...]
> +
> +static const char * const tmds181_modes[] = {
> + "redriver",
> + "auto1",
> + "auto2",
> + "retimer",
> +};
> +
> +static ssize_t mode_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct tmds181_data *data = dev_get_drvdata(dev);
> + const char *equalizer;
> + u32 val;
> + int ret;
> +
> + ret = regmap_read(data->regmap, TMDS181_REG_CTRLA, &val);
> + if (ret < 0)
> + return ret;
> +
> + if (val & BIT(4)) {
> + if (val & BIT(5))
> + equalizer = "eq-adaptive";
> + else
> + equalizer = "eq-fixed";
> + } else {
> + equalizer = "eq-disabled";
> + }
> +
> + return scnprintf(buf, PAGE_SIZE, "%6s %s %s\n",
> + (val & BIT(7)) ? "sink" : "source",
> + tmds181_modes[val & 0x03],
> + equalizer);
> +}
> +
> +static ssize_t mode_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t len)
> +{
> + struct tmds181_data *data = dev_get_drvdata(dev);
> + u32 val;
> + int ret;
> + int i;
> +
> + /* Strip trailing newline(s) for being user friendly */
> + while (len && buf[len] == '\n')
> + --len;
> +
> + /* Need at least 4 actual characters */
> + if (len < 4)
> + return -EINVAL;
> +
> + ret = regmap_read(data->regmap, TMDS181_REG_CTRLA, &val);
> + if (ret < 0)
> + return ret;
> +
> + for (i = 0; i < ARRAY_SIZE(tmds181_modes); ++i) {
> + if (strncmp(tmds181_modes[i], buf, len) == 0) {
> + val &= ~0x03;
> + val |= i;
> + break;
> + }
> + }
> +
> + if (strncmp("sink", buf, len) == 0)
> + val |= BIT(7);
> +
> + if (strncmp("source", buf, len) == 0)
> + val &= ~BIT(7);
> +
> + if (strncmp("eq-", buf, 3) == 0) {
> + switch (buf[3]) {
> + case 'a': /* adaptive */
> + val |= BIT(4) | BIT(5);
> + break;
> + case 'f': /* fixed */
> + val |= BIT(4);
> + val &= ~BIT(5);
> + break;
> + case 'd': /* disable */
> + val &= ~(BIT(4) | BIT(5));
> + break;
> + }
> + }
> +
> + /* Always set the "apply changes" bit */
> + val |= BIT(2);
> +
> + ret = regmap_write(data->regmap, TMDS181_REG_CTRLA, val);
> + if (ret < 0)
> + return ret;
> +
> + return len;
> +}
> +
> +/* termination for HDMI TX: 0=off, 1=150..300, 3=75..150 ohms */
> +static ssize_t termination_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct tmds181_data *data = dev_get_drvdata(dev);
> + u32 val;
> + int ret;
> +
> + ret = regmap_read(data->regmap, TMDS181_REG_CTRLB, &val);
> + if (ret < 0)
> + return ret;
> +
> + val >>= 3;
> + val &= 0x03;
> +
> + return scnprintf(buf, PAGE_SIZE, "%u\n", val);
> +}
> +
> +static ssize_t termination_store(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t len)
> +{
> + struct tmds181_data *data = dev_get_drvdata(dev);
> + u32 val;
> + unsigned long newval;
> + int ret;
> +
> + ret = regmap_read(data->regmap, TMDS181_REG_CTRLB, &val);
> + if (ret < 0)
> + return ret;
> +
> + ret = kstrtoul((const char *) buf, 10, &newval);
> + if (ret)
> + return ret;
> +
> + if (newval > 3)
> + return -EINVAL;
> +
> + val &= ~(0x03 << 3);
> + val |= newval << 3;
> +
> + ret = regmap_write(data->regmap, TMDS181_REG_CTRLB, val);
> + if (ret < 0)
> + return ret;
> +
> + return len;
> +}
> +
> +static DEVICE_ATTR_RW(mode);
> +static DEVICE_ATTR_RW(termination);
Undocumented ABI. Why are they configured at runtime rather than through
the DT / fwnode?
> +
> +static struct attribute *tmds181_attrs[] = {
> + &dev_attr_mode.attr,
> + &dev_attr_termination.attr,
> + NULL,
> +};
> +
> +static const struct attribute_group tmds181_attr_group = {
> + .attrs = tmds181_attrs,
> +};
> +
> +static const u8 tmds181_id_tmds181[8] = "TMDS181 ";
> +static const u8 tmds181_id_dp159[8] = "DP159 ";
> +
> +static int tmds181_check_id(struct tmds181_data *data)
> +{
> + int ret;
> + int retry;
> + u8 buffer[8];
> +
> + for (retry = 0; retry < 20; ++retry) {
> + ret = regmap_bulk_read(data->regmap, TMDS181_REG_ID, buffer,
> + sizeof(buffer));
> + if (!ret)
> + break;
> +
> + /* Compensate for very long OE power-up delays due to the cap */
> + usleep_range(5000, 10000);
> + }
> +
> + if (ret) {
> + dev_err(&data->client->dev, "I2C read ID failed\n");
> + return ret;
> + }
> +
> + if (memcmp(buffer, tmds181_id_tmds181, sizeof(buffer)) == 0) {
> + dev_info(&data->client->dev, "Detected: TMDS181\n");
> + data->chip = tmds181;
> + return 0;
> + }
> +
> + if (memcmp(buffer, tmds181_id_dp159, sizeof(buffer)) == 0) {
> + dev_info(&data->client->dev, "Detected: DP159\n");
> + data->chip = dp159;
> + return 0;
> + }
> +
> + dev_err(&data->client->dev, "Unknown or wrong ID: %*pE\n",
> (int)sizeof(buffer), buffer);
> +
> + return -ENODEV;
> +}
> +
> +static bool tmds181_regmap_is_volatile(struct device *dev, unsigned int reg)
> +{
> + switch (reg) {
> + /* IBERT result and status registers, not used yet */
> + case 0x15:
> + case 0x17 ... 0x1F:
> + return true;
> + default:
> + return false;
> + }
> +}
> +
> +static const struct regmap_config tmds181_regmap_config = {
> + .reg_bits = 8,
> + .val_bits = 8,
> + .cache_type = REGCACHE_RBTREE,
> + .max_register = 0x20,
> + .volatile_reg = tmds181_regmap_is_volatile,
> +};
> +
> +static int tmds181_probe(struct i2c_client *client)
> +{
> + struct tmds181_data *data;
> + struct gpio_desc *oe_gpio;
> + int ret;
> + u32 param;
> + u8 val;
> +
> + /* Check if the adapter supports the needed features */
> + if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_BYTE_DATA))
> + return -EIO;
> +
> + data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + data->client = client;
> + i2c_set_clientdata(client, data);
> + data->regmap = devm_regmap_init_i2c(client, &tmds181_regmap_config);
> + if (IS_ERR(data->regmap))
> + return PTR_ERR(data->regmap);
> +
> + /* The "OE" pin acts as a reset */
> + oe_gpio = devm_gpiod_get_optional(&client->dev, "oe", GPIOD_OUT_LOW);
> + if (IS_ERR(oe_gpio)) {
> + ret = PTR_ERR(oe_gpio);
> + if (ret != -EPROBE_DEFER)
> + dev_err(&client->dev, "failed to acquire 'oe' gpio\n");
> + return ret;
> + }
> + if (oe_gpio) {
> + /* Need at least 100us reset pulse */
> + usleep_range(100, 200);
> + gpiod_set_value_cansleep(oe_gpio, 1);
> + }
> +
> + /* Reading the ID also provides enough time for the reset */
> + ret = tmds181_check_id(data);
> + if (ret)
> + return ret;
> +
> + /* We take care of power control, so disable the chips PM functions */
> + /* SIG_EN=0 PD_EN=1 HPD_AUTO_PWRDWN_DISABLE=1 I2C_DR_CTL=0b11*/
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRL9, 0x1f, 0x0f);
> +
> + /* Apply configuration changes */
> + if (of_property_read_bool(client->dev.of_node, "source-mode"))
Undocumented DT properties. Please document them in DT bindings.
> + regmap_update_bits(data->regmap,
> + TMDS181_REG_CTRLA, BIT(7), 0);
> + if (of_property_read_bool(client->dev.of_node, "sink-mode"))
> + regmap_update_bits(data->regmap,
> + TMDS181_REG_CTRLA, BIT(7), BIT(7));
> + if (of_property_read_bool(client->dev.of_node, "redriver-mode"))
> + regmap_update_bits(data->regmap,
> + TMDS181_REG_CTRLA, 0x03, 0x00);
> + if (of_property_read_bool(client->dev.of_node, "retimer-mode"))
> + regmap_update_bits(data->regmap,
> + TMDS181_REG_CTRLA, 0x03, 0x03);
> + if (of_property_read_bool(client->dev.of_node, "adaptive-equalizer"))
> + regmap_update_bits(data->regmap,
> + TMDS181_REG_CTRLA, BIT(4) | BIT(5), BIT(4) | BIT(5));
> + if (of_property_read_bool(client->dev.of_node, "disable-equalizer"))
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRLA, BIT(4), 0);
> +
> + switch (data->chip) {
> + case dp159:
> + /* SLEW=0b00 Mode=HDMI DDC_TRAIN_SET=1 */
> + val = BIT(0);
> + /* Default slew rate is max */
> + param = 3;
> + if (!of_property_read_u32(client->dev.of_node,
> + "slew-rate", ¶m)) {
> + if (param > 3) {
> + dev_err(&client->dev, "invalid slew-rate\n");
> + return -EINVAL;
> + }
> + /* Implement 0 = slow, 3 = fast slew rate */
> + val = (3 - param) << 6;
> + }
> + if (of_property_read_bool(client->dev.of_node, "dvi-mode"))
> + val |= BIT(5);
> + break;
> + default:
> + /* DDC_DR_SEL=1 DDC_TRAIN_SETDISABLE=1 */
> + val = BIT(2) | BIT(0);
> + break;
> + }
> +
> + /* termination for HDMI TX: 0=off, 1=150..300, 3=75..150 ohms */
> + if (!of_property_read_u32(client->dev.of_node, "termination", ¶m))
> + val |= ((param & 0x3) << 3);
> +
> + ret = regmap_write(data->regmap, TMDS181_REG_CTRLB, val);
> + if (ret < 0) {
> + dev_err(&client->dev, "regmap_write(B) failed\n");
> + return ret;
> + }
> +
> + val = 0; /* Default for C register */
> + if (!of_property_read_u32(client->dev.of_node, "vswing-data", ¶m))
> + val |= (param << 5);
> + if (!of_property_read_u32(client->dev.of_node, "vswing-clk", ¶m))
> + val |= (param << 2);
> + /* Datasheet recommends HDMI_TWPST=0b01 for HDMI compliance */
> + if (of_property_read_bool(client->dev.of_node, "enable-de-emphasis"))
> + val |= 0x01;
> + ret = regmap_write(data->regmap, TMDS181_REG_CTRLC, val);
> + if (ret < 0) {
> + dev_err(&client->dev, "regmap_write(C) failed\n");
> + return ret;
> + }
> +
> + /* DIS_HDMI2_SWG: HDMI 1.x only, keep clock at full rate */
> + val = BIT(0);
> + if (!of_property_read_u32(client->dev.of_node, "eq-data", ¶m)) {
> + val |= (param << 3);
> + /* If defined, also force the "fixed" equalizer mode */
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRLA, BIT(5), 0);
> + }
> + if (!of_property_read_u32(client->dev.of_node, "eq-clk", ¶m)) {
> + val |= (param << 1);
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRLA, BIT(5), 0);
> + }
> + ret = regmap_write(data->regmap, TMDS181_REG_EQUALIZER, val);
> + if (ret < 0) {
> + dev_err(&client->dev, "regmap_write(EQUALIZER) failed\n");
> + return ret;
> + }
> +
> + ret = tmds181_apply_changes(data);
> + if (ret < 0) {
> + dev_err(&client->dev, "tmds181_apply_changes failed\n");
> + return ret;
> + }
> +
> + ret = sysfs_create_group(&client->dev.kobj, &tmds181_attr_group);
> + if (ret)
> + dev_err(&client->dev, "sysfs_create_group error: %d\n", ret);
> +
> + /* Find next bridge in chain */
> + data->next_bridge = devm_drm_of_get_bridge(&client->dev,
> client->dev.of_node, 1, 0);
> + if (IS_ERR(data->next_bridge))
> + return dev_err_probe(&client->dev, PTR_ERR(data->next_bridge),
> + "Failed to find next bridge\n");
> +
> + /* Register the bridge. */
> + data->bridge.funcs = &tmds181_bridge_funcs;
> + data->bridge.of_node = client->dev.of_node;
> +
> + return devm_drm_bridge_add(&client->dev, &data->bridge);
> +}
> +
> +static const struct i2c_device_id tmds181_id[] = {
> + { "tmds181", tmds181 },
> + { "sn65dp159", dp159 },
> + {}
> +};
> +MODULE_DEVICE_TABLE(i2c, tmds181_id);
> +
> +#if IS_ENABLED(CONFIG_OF)
> +static const struct of_device_id tmds181_of_match[] = {
> + { .compatible = "ti,tmds181", },
> + { .compatible = "ti,sn65dp159", },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, tmds181_of_match);
> +#endif
> +
> +static struct i2c_driver tmds181_driver = {
> + .driver = {
> + .owner = THIS_MODULE,
> + .name = "tmds181",
> + .of_match_table = of_match_ptr(tmds181_of_match),
> + },
> + .probe = tmds181_probe,
> + .id_table = tmds181_id,
> +};
> +
> +module_i2c_driver(tmds181_driver);
> --
> 2.43.0
>
>
> Met vriendelijke groet / kind regards,
>
> Mike Looijmans
> System Expert
>
>
> TOPIC Embedded Products B.V.
> Materiaalweg 4, 5681 RJ Best
> The Netherlands
>
> T: +31 (0) 499 33 69 69
> E: mike.looijm...@topic.nl
> W: www.topic.nl
>
> Please consider the environment before printing this e-mail
--
With best wishes
Dmitry
