linux-kernel - Re: [PATCH 3/6] drm/bridge: display-connector: allow YCbCr 420 for HDMI and DP

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Message-ID: <88d16fd7-eac5-447b-8926-00eb8bafe3ff@linaro.org>
Date: Mon, 21 Oct 2024 11:54:02 +0200
From: neil.armstrong@...aro.org
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Andrzej Hajda <andrzej.hajda@...el.com>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Rob Clark <robdclark@...il.com>, Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Sean Paul <sean@...rly.run>, Marijn Suijten <marijn.suijten@...ainline.org>,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org
Subject: Re: [PATCH 3/6] drm/bridge: display-connector: allow YCbCr 420 for
 HDMI and DP

On 21/10/2024 11:06, Dmitry Baryshkov wrote:
> On Mon, 21 Oct 2024 at 10:29, Neil Armstrong <neil.armstrong@...aro.org> wrote:
>>
>> On 18/10/2024 23:49, Dmitry Baryshkov wrote:
>>> Allow YCbCr 420 output for HDMI and DisplayPort connectors. Other
>>> bridges in the chain still might limit YCbCr 420 support on the
>>> corresponding connector.
>>>
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>> ---
>>>    drivers/gpu/drm/bridge/display-connector.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/bridge/display-connector.c b/drivers/gpu/drm/bridge/display-connector.c
>>> index ab8e00baf3f1..aab9ce7be94c 100644
>>> --- a/drivers/gpu/drm/bridge/display-connector.c
>>> +++ b/drivers/gpu/drm/bridge/display-connector.c
>>> @@ -270,6 +270,10 @@ static int display_connector_probe(struct platform_device *pdev)
>>>        /* All the supported connector types support interlaced modes. */
>>>        conn->bridge.interlace_allowed = true;
>>>
>>> +     if (type == DRM_MODE_CONNECTOR_HDMIA ||
>>> +         type == DRM_MODE_CONNECTOR_DisplayPort)
>>> +             conn->bridge.ycbcr_420_allowed = true;
>>> +
>>>        /* Get the optional connector label. */
>>>        of_property_read_string(pdev->dev.of_node, "label", &label);
>>>
>>>
>>
>> I think we should make sure all HDMI bridges can filter out 420 before
>> landing this, no ?
> 
> No, it's the other way around: if one of the bridges in a chain
> doesn't set 420_allowed, then 420_allowed won't be set for the
> connector, disallowing YCbCr 420 modes.
> Before this patchset the bridge / platform drivers had to manually set
> the flag on the created connector (see dw-hdmi + meson-encoder-hdmi or
> msm/dp).
> 

Right, sorry for the noise...

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>