linux-kernel - Re: [PATCH v6 4/5] drm/panel-edp: Add override_edid

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Date:   Wed, 8 Nov 2023 09:04:09 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Maxime Ripard <mripard@...nel.org>
Cc:     Hsin-Yi Wang <hsinyi@...omium.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        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,
        stable@...r.kernel.org
Subject: Re: [PATCH v6 4/5] drm/panel-edp: Add override_edid_mode quirk for
 generic edp

Hi,

On Wed, Nov 8, 2023 at 7:45 AM Maxime Ripard <mripard@...nel.org> wrote:
>
> > @@ -575,9 +599,18 @@ static int panel_edp_get_modes(struct drm_panel *panel,
> >
> >               if (!p->edid)
> >                       p->edid = drm_get_edid(connector, p->ddc);
> > -
> > -             if (p->edid)
> > -                     num += drm_add_edid_modes(connector, p->edid);
> > +             if (p->edid) {
> > +                     if (has_override_edid_mode) {
>
> It's not clear to me why the override mechanism is only there when
> there's a ddc bus?

I think you're confusing the two different (but related) issues
addressed by this series. One is when you're using the generic
"edp-panel" compatible string. In that case the mode comes from the
EDID and only the EDID since there's no hardcoded mode. We need a mode
override there since some EDIDs shipped with a bad mode. That's the
subject of ${SUBJECT} patch.

The second issue is what to do with a hardcoded mode. That's the
subject of the next patch in the series (patch #5). Previously we
merged the hardcoded and EDID modes. Now (in the next patch) we use
only the hardcoded mode. There's no need for a fixup because the mode
is hardcoded in the kernel.

> You mentioned before that you were following panel-simple,

As of the newest version of the patch, it's no longer following
panel-simple in response to your feedback on previous versions.

> but that's a
> clear deviation from what I can see. If there's a reason for that
> deviation, that's fine by me, but it should at least be documented in
> the commit log.

I think the commit log is OK. I suspect the confusion is only because
you've reviewed previous versions of the series. Please shout if
things still look confusing.

> > @@ -950,6 +983,19 @@ static const struct panel_desc auo_b101ean01 = {
> >       },
> >  };
> >
> > +static const struct drm_display_mode auo_b116xa3_mode = {
> > +     .clock = 70589,
> > +     .hdisplay = 1366,
> > +     .hsync_start = 1366 + 40,
> > +     .hsync_end = 1366 + 40 + 40,
> > +     .htotal = 1366 + 40 + 40 + 32,
> > +     .vdisplay = 768,
> > +     .vsync_start = 768 + 10,
> > +     .vsync_end = 768 + 10 + 12,
> > +     .vtotal = 768 + 10 + 12 + 6,
> > +     .flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
> > +};
>
> That should be a separate patch

That's fair. I didn't think it was a huge deal, but I agree that it's
slightly cleaner.

-Doug