linux-kernel - Re: [PATCH v3 3/3] drm/panel-edp: Avoid adding multiple preferred modes

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Date:   Mon, 6 Nov 2023 12:38:26 -0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Neil Armstrong <neil.armstrong@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] drm/panel-edp: Avoid adding multiple preferred modes

On Mon, Nov 6, 2023 at 12:33 PM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Mon, Nov 6, 2023 at 12:27 PM Hsin-Yi Wang <hsinyi@...omium.org> wrote:
> >
> > diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
> > index 0fb439b5efb1..54dbbdf62ec0 100644
> > --- a/drivers/gpu/drm/panel/panel-edp.c
> > +++ b/drivers/gpu/drm/panel/panel-edp.c
> > @@ -594,8 +594,20 @@ static int panel_edp_get_modes(struct drm_panel *panel,
> >                                       p->detected_panel != ERR_PTR(-EINVAL) &&
> >                                       p->detected_panel->override_edid_mode;
> >
> > -       /* probe EDID if a DDC bus is available */
> > -       if (p->ddc) {
> > +       /*
> > +        * If both edid and hard-coded modes exists, only add hard-coded modes
> > +        * to avoid multiple preferred modes.
> > +        */
> > +       if (p->desc->num_timings || p->desc->num_modes) {
> > +               /*
> > +                * Add hard-coded panel modes. Don't call this if there are no
> > +                * timings and no modes (the generic edp-panel case) because it
> > +                * will clobber the display_info that was already set by
> > +                * drm_add_edid_modes().
> > +                */
> > +               num += panel_edp_get_non_edid_modes(p, connector);
> > +       } else if (p->ddc) {
> > +               /* probe EDID if a DDC bus is available */
>
> As per discussion in v2, I think if you have the "ddc" you still want
> to fetch the EDID, you just don't want to add the modes from the EDID.
> This will mean that the EDID is present in sysfs if userspace wants to
> look at it for whatever reason.
>
Ack. Will update this.

> -Doug