linux-kernel - Re: [PATCH] drm/msm/dsi: Set panel orientation when directly connected

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Message-ID: <CAA8EJpo-CS9ZUzA7wDZ05W+Wcz9P_1fXHYPaZACEhMOjnJv_Yg@mail.gmail.com>
Date:   Fri, 8 Jul 2022 23:58:51 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     Doug Anderson <dianders@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, patches@...ts.linux.dev,
        Sean Paul <sean@...rly.run>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>
Subject: Re: [PATCH] drm/msm/dsi: Set panel orientation when directly connected

On Fri, 8 Jul 2022 at 22:42, Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>
>
>
> On 7/8/2022 9:00 AM, Abhinav Kumar wrote:
> >
> >
> > On 7/8/2022 8:25 AM, Doug Anderson wrote:
> >> Hi,
> >>
> >> On Wed, Jul 6, 2022 at 12:14 PM Stephen Boyd <swboyd@...omium.org> wrote:
> >>>
> >>> Set the panel orientation in drm when the panel is directly connected,
> >>> i.e. we're not using an external bridge. The external bridge case is
> >>> already handled by the panel bridge code, so we only update the path we
> >>> take when the panel is directly connected/internal. This silences a
> >>> warning splat coming from __drm_mode_object_add() on Wormdingler boards.
> >>>
> >>> Cc: Hsin-Yi Wang <hsinyi@...omium.org>
> >>> Cc: Douglas Anderson <dianders@...omium.org>
> >>> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> >>> ---
> >>>
> >>> This relies on commit 5e41b01a7808 ("drm/panel: Add an API to allow drm
> >>> to set orientation from panel") which is in drm-misc
> >>>
> >>>   drivers/gpu/drm/msm/dsi/dsi_manager.c | 2 ++
> >>>   1 file changed, 2 insertions(+)
> >>
> >> I don't personally have objections to this, but (to my understanding)
> >> "the future" is that everyone should use panel_bridge. If we made the
> >> move to panel_bridge today then we wouldn't need to do this. In
> >> general I think panel_bridge would end up letting us delete a bunch of
> >> code...
> >>
> >> See commit 4e5763f03e10 ("drm/bridge: ti-sn65dsi86: Wrap panel with
> >> panel-bridge") for when this was done by ti-sn65dsi86.
> >>
> >> Then again, I spent a small amount of time looking into this and it's
> >> definitely non-trivial. Still likely worthwhile, but not worth
> >> blocking a tiny fix like this. It also should be fairly obvious that
> >> we should delete this when we switch to panel_bridge.
> >
> > Right, from what I saw on IRC, panel_bridge is the way forward and
> > dmitry did push a change to do that
> >
> > https://patchwork.freedesktop.org/patch/492585/
> >
> > But I think we can go ahead with this change because its simple enough.
> >
> > Regarding the panel_bridge migration, I am going to start reviewing that
> > as well.
> >
>
> I did some more digging up on the panel_bridge migration.
>
> Dmitry has posted this towards december last year
>
> https://patches.linaro.org/project/dri-devel/patch/20211207222901.988484-3-dmitry.baryshkov@linaro.org/
>
>
> and I had given my R-b on this already in Jan.
>
> I am not sure why this change was dropped OR was not part of msm-next
> already.
>
> Dmitry, any reason this change was left out so long and why the R-b was
> not retained and this was reposted?
>
>  From what i can see the change looks identical.

I don't remember if it is identical or not. Basically it was postponed
to allow DSC to flow in. We used drm_panel to pass DSC pps data. And
if we use panel-bridge, we don't get a handle of the panel.
Later on I have posted the series moving DSC pps pointer from
drm_panel to mipi_dsi_device (which is logical anyway, since it's not
only the panel, who can provide the DSC pps info, some bridges can
process DSC-compressed data). But since that time it received no
feedback.


-- 
With best wishes
Dmitry