On Wed, Aug 20, 2025 at 04:40:35PM +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 <[email protected]>
> ---
>
> Changes in v3:
> Lower-case hex values and use defines for EYESCAN registers
> Remove equalizer code (unlikely to be used)
> Remove attributes (no longer useful, undocumented)
> Fix build for 6.17 kernel
> Use devm_drm_bridge_alloc
> Sort includes and add linux/bitfield.h
> Check chip type and complain on mismatch
>
> Changes in v2:
> Use atomic_enable/disable
> Use #defines for bit fields in registers
> Allow HDMI 2 compliance
> Filter modes on clock range
> Use cross-over pixel frequency instead of manual overides
> Devicetree bindings according to standards
>
> drivers/gpu/drm/bridge/Kconfig | 11 +
> drivers/gpu/drm/bridge/Makefile | 1 +
> drivers/gpu/drm/bridge/ti-tmds181.c | 409 ++++++++++++++++++++++++++++
> 3 files changed, 421 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..8ac3eb808d5b
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/ti-tmds181.c
> @@ -0,0 +1,409 @@
> +// 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 <[email protected]>
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/regmap.h>
> +#include <linux/slab.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
> +/* EYESCAN registers don't appear to deserve separate names */
> +#define TMDS181_REG_EYESCAN_E 0xe
> +#define TMDS181_REG_EYESCAN_F 0xf
> +#define TMDS181_REG_EYESCAN_15 0x15
> +#define TMDS181_REG_EYESCAN_17 0x17
> +#define TMDS181_REG_EYESCAN_1F 0x1f
> +#define TMDS181_REG_AUX 0x20
> +
> +
> +#define TMDS181_CTRL9_SIG_EN BIT(4)
> +#define TMDS181_CTRL9_PD_EN BIT(3)
> +#define TMDS181_CTRL9_HPD_AUTO_PWRDWN_DISABLE BIT(2)
> +#define TMDS181_CTRL9_I2C_DR_CTL GENMASK(1, 0)
> +
> +#define TMDS181_CTRLA_MODE_SINK BIT(7)
> +#define TMDS181_CTRLA_HPDSNK_GATE_EN BIT(6)
> +#define TMDS181_CTRLA_EQ_ADA_EN BIT(5)
> +#define TMDS181_CTRLA_EQ_EN BIT(4)
> +#define TMDS181_CTRLA_AUX_BRG_EN BIT(3)
> +#define TMDS181_CTRLA_APPLY BIT(2)
> +#define TMDS181_CTRLA_DEV_FUNC_MODE GENMASK(1, 0)
> +
> +#define TMDS181_CTRLB_SLEW_CTL GENMASK(7, 6)
> +#define TMDS181_CTRLB_HDMI_SEL_DVI BIT(5)
> +#define TMDS181_CTRLB_TX_TERM_CTL GENMASK(4, 3)
> +#define TMDS181_CTRLB_DDC_DR_SEL BIT(2)
> +#define TMDS181_CTRLB_TMDS_CLOCK_RATIO_STATUS BIT(1)
> +#define TMDS181_CTRLB_DDC_TRAIN_SET BIT(0)
> +
> +#define TMDS181_CTRLB_TX_TERM_150_300_OHMS 1
> +#define TMDS181_CTRLB_TX_TERM_75_150_OHMS 3
> +
> +#define TMDS181_CTRLC_VSWING_DATA GENMASK(7, 5)
> +#define TMDS181_CTRLC_VSWING_CLK GENMASK(4, 2)
> +#define TMDS181_CTRLC_HDMI_TWPST1 GENMASK(1, 0)
> +
> +#define TMDS181_EQ_DATA_LANE GENMASK(5, 3)
> +#define TMDS181_EQ_CLOCK_LANE GENMASK(2, 1)
> +#define TMDS181_EQ_DIS_HDMI2_SWG BIT(0)
> +
> +/* Above this data rate HDMI2 standards apply (TX termination) */
> +#define HDMI2_PIXEL_RATE_KHZ 340000
> +
> +enum tmds181_chip {
> + tmds181,
> + dp159,
> +};
> +
> +struct tmds181_data {
> + struct i2c_client *client;
> + struct regmap *regmap;
> + struct drm_bridge *next_bridge;
> + struct drm_bridge bridge;
> + u32 retimer_threshold_khz;
> +};
> +
> +static inline struct tmds181_data *
> +drm_bridge_to_tmds181_data(struct drm_bridge *bridge)
> +{
> + return container_of(bridge, struct tmds181_data, bridge);
> +}
> +
> +static int tmds181_attach(struct drm_bridge *bridge, struct drm_encoder
> *encoder,
> + enum drm_bridge_attach_flags flags)
> +{
> + struct tmds181_data *data = drm_bridge_to_tmds181_data(bridge);
> +
> + return drm_bridge_attach(encoder, data->next_bridge, bridge, flags);
> +}
> +
> +static enum drm_mode_status
> +tmds181_mode_valid(struct drm_bridge *bridge, const struct drm_display_info
> *info,
> + const struct drm_display_mode *mode)
> +{
> + /* Clock limits: clk between 25 and 350 MHz, clk is 1/10 of bit clock */
> + if (mode->clock < 25000)
> + return MODE_CLOCK_LOW;
> +
> + /* The actual HDMI clock (if provided) cannot exceed 350MHz */
> + if (mode->crtc_clock > 350000)
> + return MODE_CLOCK_HIGH;
> +
> + /*
> + * When in HDMI 2 mode, the clock is 1/40th of the bitrate. The limit is
> + * then the data rate of 6Gbps, which would use a 600MHz pixel clock.
> + */
> + if (mode->clock > 600000)
> + return MODE_CLOCK_HIGH;
> +
> + return MODE_OK;
> +}
> +
> +static void tmds181_enable(struct drm_bridge *bridge, struct
> drm_atomic_state *state)
> +{
> + struct tmds181_data *data = drm_bridge_to_tmds181_data(bridge);
> + const struct drm_crtc_state *crtc_state;
> + const struct drm_display_mode *mode;
> + struct drm_connector *connector;
> + struct drm_crtc *crtc;
> + unsigned int val;
> +
> + /*
> + * Retrieve the CRTC adjusted mode. This requires a little dance to go
> + * from the bridge to the encoder, to the connector and to the CRTC.
> + */
> + connector = drm_atomic_get_new_connector_for_encoder(state,
> + bridge->encoder);
> + crtc = drm_atomic_get_new_connector_state(state, connector)->crtc;
> + crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
> + mode = &crtc_state->adjusted_mode;
> +
> + /* Set retimer/redriver mode based on pixel clock */
> + val = mode->clock > data->retimer_threshold_khz ?
> TMDS181_CTRLA_DEV_FUNC_MODE : 0;
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRLA,
> + TMDS181_CTRLA_DEV_FUNC_MODE, val);
> +
> + /* Configure TX termination based on pixel clock */
> + val = mode->clock > HDMI2_PIXEL_RATE_KHZ ?
> + TMDS181_CTRLB_TX_TERM_75_150_OHMS :
> + TMDS181_CTRLB_TX_TERM_150_300_OHMS;
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRLB,
> + TMDS181_CTRLB_TX_TERM_CTL,
> + FIELD_PREP(TMDS181_CTRLB_TX_TERM_CTL, val));
> +
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRL9,
> + TMDS181_CTRL9_PD_EN, 0);
> +}
> +
> +static void tmds181_disable(struct drm_bridge *bridge, struct
> drm_atomic_state *state)
> +{
> + struct tmds181_data *data = drm_bridge_to_tmds181_data(bridge);
> +
> + /* Set the PD_EN bit */
> + regmap_update_bits(data->regmap, TMDS181_REG_CTRL9,
> + TMDS181_CTRL9_PD_EN, TMDS181_CTRL9_PD_EN);
> +}
> +
> +static const struct drm_bridge_funcs tmds181_bridge_funcs = {
> + .attach = tmds181_attach,
> + .mode_valid = tmds181_mode_valid,
> + .atomic_enable = tmds181_enable,
> + .atomic_disable = tmds181_disable,
> +
> + .atomic_reset = drm_atomic_helper_bridge_reset,
> + .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> + .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> +};
> +
> +static const u8 tmds181_id_tmds181[8] __nonstring = "TMDS181 ";
> +static const u8 tmds181_id_dp159[8] __nonstring = "DP159 ";
> +
> +static int tmds181_check_id(struct tmds181_data *data, enum tmds181_chip
> *chip)
> +{
> + 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) {
> + if (*chip != tmds181) {
> + dev_warn(&data->client->dev, "Detected: TMDS181\n");
> + *chip = tmds181;
> + }
> + return 0;
> + }
> +
> + if (memcmp(buffer, tmds181_id_dp159, sizeof(buffer)) == 0) {
> + if (*chip != dp159) {
> + dev_warn(&data->client->dev, "Detected: DP159\n");
> + *chip = dp159;
> + }
> + return 0;
> + }
> +
> + dev_err(&data->client->dev, "Unknown 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 TMDS181_REG_EYESCAN_15:
> + case TMDS181_REG_EYESCAN_17 ... TMDS181_REG_EYESCAN_1F:
> + 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 = TMDS181_REG_AUX,
> + .volatile_reg = tmds181_regmap_is_volatile,
> +};
> +
> +static int tmds181_probe(struct i2c_client *client)
> +{
> + struct tmds181_data *data;
> + struct gpio_desc *oe_gpio;
> + enum tmds181_chip chip;
> + 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_drm_bridge_alloc(&client->dev, struct tmds181_data, bridge,
> + &tmds181_bridge_funcs);
> + if (IS_ERR(data))
> + return PTR_ERR(data);
> +
> + 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");
Heh, nice...
> + return ret;
> + }
...
> +
> +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", .data = (void *)tmds181 },
> + { .compatible = "ti,sn65dp159", .data = (void *)dp159 },
> + {}
> +};
> +MODULE_DEVICE_TABLE(of, tmds181_of_match);
> +#endif
> +
> +static struct i2c_driver tmds181_driver = {
> + .driver = {
> + .owner = THIS_MODULE,
Nice coincidence - this stars in one of my talks on OSSE
(https://sched.co/25VoV) as my litmus test for crazy old, vendor code.
Please come to the session if you are around or just check the slides
afterwards.
The open-coding dev_err_probe() is another great example.
Best regards,
Krzysztof
