linux-kernel - Re: [PATCH v3 2/5] drm/bridge: simple: add Realtek RTD2171 DP-to-HDMI bridge

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Message-ID: <a0d8f2de-2456-4f18-b901-e8b003eece44@linaro.org>
Date: Mon, 8 Sep 2025 16:07:22 +0200
From: neil.armstrong@...aro.org
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
 Maud Spierings <maud_spierings@...mail.com>
Cc: Laurent.pinchart@...asonboard.com, airlied@...il.com,
 andersson@...nel.org, andrzej.hajda@...el.com, conor+dt@...nel.org,
 devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 jernej.skrabec@...il.com, jonas@...boo.se, kishon@...nel.org,
 konradybcio@...nel.org, krzk+dt@...nel.org, linux-arm-msm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, rfoss@...nel.org,
 robh@...nel.org, simona@...ll.ch, tzimmermann@...e.de, vkoul@...nel.org
Subject: Re: [PATCH v3 2/5] drm/bridge: simple: add Realtek RTD2171 DP-to-HDMI
 bridge

Hi,

On 08/09/2025 15:45, Dmitry Baryshkov wrote:
> On Mon, Sep 08, 2025 at 03:35:23PM +0200, Maud Spierings wrote:
>> Hello Neil,
>>
>>> Add support for the transparent Realtek RTD2171 DP-to-HDMI bridge.
>>>
>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>>> ---
>>>   drivers/gpu/drm/bridge/simple-bridge.c | 5 +++++
>>>   1 file changed, 5 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
>>> index 1f16d568bcc4e0fb56c763244389e6fecbcb2231..e4d0bc2200f8632bcc883102c89c270a17c68d0c 100644
>>> --- a/drivers/gpu/drm/bridge/simple-bridge.c
>>> +++ b/drivers/gpu/drm/bridge/simple-bridge.c
>>> @@ -266,6 +266,11 @@ static const struct of_device_id simple_bridge_match[] = {
>>>   		.data = &(const struct simple_bridge_info) {
>>>   			.connector_type = DRM_MODE_CONNECTOR_HDMIA,
>>>   		},
>>> +	}, {
>>> +		.compatible = "realtek,rtd2171",
>>> +		.data = &(const struct simple_bridge_info) {
>>> +			.connector_type = DRM_MODE_CONNECTOR_HDMIA,
>>> +		},
>>>   	}, {
>>>   		.compatible = "ti,opa362",
>>>   		.data = &(const struct simple_bridge_info) {
>>>
>>> -- 
>>> 2.34.1
>>
>> I would like to ask again if it may not be a better idea to introduce a
>> fallback compatible, once this patchseries lands I will be adding the
> 
> I'd say, that's not a good idea. We usually don't have fully datasheets
> for those bridges, so we can't be sure that there are no strapping pins
> / other GPIO controls.
> 
>> parade,ps185hdm. I don't know how many other variants there are that are
>> just simple dp->hdmi bridges that don't require anything other than the
>> connector type set to HDMIA. The Thinkbook 16 and zenbook a14 both have HDMI
>> connectors, likely with simple bridges too.

Sorry for the late reply, yes I have the same position, they are simple bridge
until we found out it's not the case...

Neil

>>
>> Kind regards,
>> Maud
>