linux-kernel - Re: [PATCH 2/2] drm: bridge: Add TI tmds181 and sn65dp159 driver

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Message-ID: <fcee104e-08f5-4502-b4ea-ffe7d42ba86a@topic.nl>
Date: Tue, 19 Aug 2025 13:19:13 +0200
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
CC: dri-devel@...ts.freedesktop.org, Andrzej Hajda <andrzej.hajda@...el.com>,
 David Airlie <airlied@...il.com>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Jonas Karlman <jonas@...boo.se>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Simona Vetter <simona@...ll.ch>, Thomas Zimmermann <tzimmermann@...e.de>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm: bridge: Add TI tmds181 and sn65dp159 driver

On 19-08-2025 12:26, Dmitry Baryshkov wrote:
> 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.looijmans@...ic.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 <leon@...ebranch.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.

Will change in v3


>> ...
>> +	/* Apply configuration changes */
>> +	if (of_property_read_bool(client->dev.of_node, "source-mode"))
> Undocumented DT properties. Please document them in DT bindings.

Damn, this is the wrong version of the file, this looks like it's just 
v1 again. I'll post v3 ASAP.


> ...


-- 
Mike Looijmans