linux-kernel - Re: [PATCH v2 0/5] 180 degrees rotation support for NVIDIA Tegra DRM

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Message-ID: <8f789ef5-bebf-c869-784d-afda70fc1fb8@gmail.com>
Date:   Tue, 16 Jun 2020 14:40:47 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Emil Velikov <emil.l.velikov@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Derek Basehore <dbasehore@...omium.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sean Paul <sean@...rly.run>, linux-tegra@...r.kernel.org,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v2 0/5] 180 degrees rotation support for NVIDIA Tegra DRM

16.06.2020 01:26, Emil Velikov пишет:
> Hi Dmitry,
> 
> On Mon, 15 Jun 2020 at 08:28, Dmitry Osipenko <digetx@...il.com> wrote:
>>
>> Hello!
>>
>> This series adds 180° display plane rotation support to the NVIDIA Tegra
>> DRM driver which is needed for devices that have display panel physically
>> mounted upside-down, like Nexus 7 tablet device for example [1]. Since
>> DRM panel rotation is a new thing for a userspace, currently only
>> Opentegra Xorg driver handles the rotated display panel [2], but this
>> is good enough for the start.
>>
>> Note that later on it should be possible to implement a transparent 180°
>> display rotation for Tegra DRM driver which will remove the need to have
>> a bleeding edge userspace that knows how to rotate display planes and I'm
>> slowly working on it. For the starter we can go with the minimal rotation
>> support, so it's not a blocker.
>>
>> This series is based on the work that was made by Derek Basehore for the
>> Mediatek driver [3], his patch is included into this patchset. I added
>> my tested-by tag to the Derek's patch.
>>
>> Please review and apply, thanks in advance!
>>
>> [1] https://patchwork.ozlabs.org/project/linux-tegra/patch/20200607154327.18589-3-digetx@gmail.com/
>> [2] https://github.com/grate-driver/xf86-video-opentegra/commit/28eb20a3959bbe5bc3a3b67e55977093fd5114ca
>> [3] https://lkml.org/lkml/2020/3/5/1119
>>
>> Changelog:
>>
>> v2: - Dropped "drm/panel: Set display info in panel attach" patch, which
>>       turned out to be obsolete now.
>>
>>     - Renamed the cover-latter, hopefully this will fix the bouncing emails.
>>
>> Derek Basehore (1):
>>   drm/panel: Add helper for reading DT rotation
>>
>> Dmitry Osipenko (4):
>>   drm/panel: lvds: Set up panel orientation
> 
> IMHO it's perfectly reasonable to report the panel orientation to
> userspace, which can apply plane rotation as needed.
> 
> Although I see that this series, alike Derek's, has a couple of issues:
>  - only a single panel driver is updated
>  - rotation is _not_ listed as supported property, in said panel
> driver device-tree bindings
> 
> My personal inclination is that we should aim for a comprehensive solution:
>  - wire all panel drivers, as currently documented (quick grep list below)
>  - document and wire-up the lvds and boe panels - as proposed by you
> and Derek respectively
> 
> HTH
> Emil
> 
> Documentation/devicetree/bindings/display/himax,hx8357d.txt:2
> Documentation/devicetree/bindings/display/ilitek,ili9225.txt:2
> Documentation/devicetree/bindings/display/ilitek,ili9341.txt:2
> Documentation/devicetree/bindings/display/ilitek,ili9486.yaml:2
> Documentation/devicetree/bindings/display/multi-inno,mi0283qt.txt:2
> Documentation/devicetree/bindings/display/panel/panel-common.yaml:2
> Documentation/devicetree/bindings/display/sitronix,st7586.txt:1
> Documentation/devicetree/bindings/display/sitronix,st7735r.yaml:2

Rotation is a common DT panel property that is described in the
panel-common.yaml. This property is supported by all panel bindings
because these bindings inherent the common properties from the
panel-common.yaml.

I don't think that it makes sense to wire up rotation property to all
panel drivers at once because those drivers will be untested, at least I
don't know anything about those other panels and can't test them. It
will be much better to support the rotation on by as-needed basis for
each panel driver individually.