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

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Message-ID: <f4a9e0a6-fe8d-cec5-6b46-30ca4cdaeb0a@quicinc.com>
Date:   Fri, 8 Jul 2022 14:17:26 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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 7/8/2022 1:58 PM, Dmitry Baryshkov wrote:
> 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.

Thanks for the details.

I will try to review the DRM core bits. But I guess for them to land, we 
need some of the core maintainers to pitch in on that.


> 
>