linux-kernel - Re: [PATCH] drm/display: hdmi: Do not read EDID on disconnected connectors

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Message-ID: <78046727-0d2a-4ada-b75c-ec2e80e1f560@collabora.com>
Date: Mon, 13 Jan 2025 14:13:10 +0200
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Maxime Ripard <mripard@...nel.org>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/display: hdmi: Do not read EDID on disconnected
 connectors

On 1/13/25 2:06 PM, Dmitry Baryshkov wrote:
> On Mon, 13 Jan 2025 at 14:00, Cristian Ciocaltea
> <cristian.ciocaltea@...labora.com> wrote:
>>
>> Hi Maxime,
>>
>> On 1/13/25 11:35 AM, Maxime Ripard wrote:
>>> On Sat, Jan 11, 2025 at 12:04:09AM +0200, Cristian Ciocaltea wrote:
>>>> The recently introduced hotplug event handler in the HDMI Connector
>>>> framework attempts to unconditionally read the EDID data, leading to a
>>>> bunch of non-harmful, yet quite annoying DDC/I2C related errors being
>>>> reported.
>>>>
>>>> Ensure the operation is performed only for connectors having the status
>>>> connected or unknown.
>>>>
>>>> Fixes: ab716b74dc9d ("drm/display/hdmi: implement hotplug functions")
>>>> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
>>>> ---
>>>>  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 2 ++
>>>>  1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>>>> index 2691e8b3e480131ac6e4e4b74b24947be55694bd..8e4b30e09b53b84cfd36199d56db3221a00085b0 100644
>>>> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>>>> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
>>>> @@ -786,8 +786,10 @@ drm_atomic_helper_connector_hdmi_update(struct drm_connector *connector,
>>>>      const struct drm_edid *drm_edid;
>>>>
>>>>      if (status == connector_status_disconnected) {
>>>> +            drm_edid_connector_update(connector, NULL);
>>>
>>> Why is this needed? It's not mentionned in your commit log.
>>
>> The original implementation has it after reading the EDID, but I'm not
>> sure if we need the explicit reset in this case.
>>
>> I was going to submit a new revision switching the order, as Dmitry
>> suggested, or should we simply drop it?
> 
> If the EDID is not available, it needs to be reset.

Thanks for the confirmation - I will mention this in the commit description.

Regards,
Cristian