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Subject: Re: [PATCH v2 0/5] 180 degrees rotation support for NVIDIA Tegra DRM
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Emil Velikov <emil.l.velikov@gmail.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Derek Basehore <dbasehore@chromium.org>,
        Sam Ravnborg <sam@ravnborg.org>, Sean Paul <sean@poorly.run>,
        linux-tegra@vger.kernel.org,
        "Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
        ML dri-devel <dri-devel@lists.freedesktop.org>
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From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <2862a842-322e-34d6-6826-3b3352f98230@gmail.com>
Date:   Wed, 17 Jun 2020 00:25:38 +0300
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16.06.2020 20:45, Laurent Pinchart пишет:
> On Tue, Jun 16, 2020 at 08:20:57PM +0300, Dmitry Osipenko wrote:
>> 16.06.2020 18:48, Emil Velikov пишет:
>>> On Tue, 16 Jun 2020 at 12:40, Dmitry Osipenko <digetx@gmail.com> wrote:
>>>>
>>>> 16.06.2020 01:26, Emil Velikov пишет:
>>>>> Hi Dmitry,
>>>>>
>>>>> On Mon, 15 Jun 2020 at 08:28, Dmitry Osipenko <digetx@gmail.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.
>>> The property was introduced almost exclusively for tiny drm panels.
>>> Those ones are a bit different from the rest (in panel/) -
>>> MIPI-DBI/SPI w/o (not connected at least) an actual GPU.
>>>
>>> To make it a bit better, the rotation is seemingly performed in the
>>> tiny driver itself ouch.
>>>
>>>> This property is supported by all panel bindings
>>>> because these bindings inherent the common properties from the
>>>> panel-common.yaml.
>>>>
>>> Seems like that was an unintentional change with the conversion to YAML.
>>> Beforehand only a few selected panels had rotation. Upon closer look -
>>> some panels do have follow-up fixes, to remove/limit the implicit
>>> inclusion.
>>
>> Interesting.. my understanding that the rotation property is supposed to
>> be a generic property which represents physical orientation of a display
>> panel and hence it should be applicable to all panels.
> 
> Adding a bit more food for thoughts, the DT rotation property for camera
> sensor modules has recently been documented with lots of details. See
> https://lore.kernel.org/linux-media/20200509090456.3496481-3-jacopo@jmondi.org/,
> part of the documentation may be useful for panels.

Thanks!