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

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Message-ID: <CAA8EJpqzGZx0PdPKZMEwf3iv9pfb+Cr6Mrjt+p21rUwN-RiNvQ@mail.gmail.com>
Date: Mon, 13 Jan 2025 14:06:59 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
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 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,
> Cristian
>
> >
> >>              // TODO: also handle CEC and scramber, HDMI sink disconnected.
> >>              drm_connector_hdmi_audio_plugged_notify(connector, false);
> >> +            return;
> >>      }
> >>
> >>      if (connector->hdmi.funcs->read_edid)
> >
> > Maxime
>


-- 
With best wishes
Dmitry