linux-kernel - Re: [PATCH v2 0/8] Add a panel API to return panel orientation

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Date:   Thu, 2 Jun 2022 16:07:14 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     CK Hu <ck.hu@...iatek.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Rob Clark <robdclark@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-mediatek@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 0/8] Add a panel API to return panel orientation

On Thu, Jun 2, 2022 at 4:03 PM CK Hu <ck.hu@...iatek.com> wrote:
>
> Hi, Hsin-Yi:
>
> I'm curious that panel driver setting orientation in get_modes() would
> work or not. It it works, why not just set orientation in get_modes()?
> I find that exynos dsi driver has implement the get_modes() [1] but
> Mediatek dsi does not implement. Would you try this?

It's explained in the cover letter:
```
Panels usually call drm_connector_set_panel_orientation(), which is
later than drm/kms driver calling drm_dev_register(). This leads to a
WARN()[1].
```
If the get_modes() in dsi is still being called later than bind(),
then the same issue still appears.
The purpose is to set the property before drm_dev_register().



>
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/exynos/exynos_drm_dsi.c?h=v5.18#n1483
>
> Regards,
> CK
>
> On Wed, 2022-06-01 at 17:46 +0800, Hsin-Yi Wang wrote:
> > Panels usually call drm_connector_set_panel_orientation(), which is
> > later than drm/kms driver calling drm_dev_register(). This leads to a
> > WARN()[1].
> >
> > The orientation property is known earlier. For example, some panels
> > parse the property through device tree during probe.
> >
> > The series add a panel API drm_panel_get_orientation() for drm/kms
> > drivers. The drivers can use the API to get panel's orientation, so
> > they
> > can call drm_connector_set_panel_orientation() before
> > drm_dev_register().
> >
> > Panel needs to implement .get_orientation callback to return the
> > property.
> >
> > [1]
> > https://urldefense.com/v3/__https://patchwork.kernel.org/project/linux-mediatek/patch/20220530081910.3947168-2-hsinyi@chromium.org/__;!!CTRNKA9wMg0ARbw!0ytf4wPxKANnYbw_fgq-eqQARnAXIHv4jwu04ZW6X6dAxZDFsJ0CltY_PvCBAQ$
> >
> >
> > Hsin-Yi Wang (8):
> >   drm/panel: Add an API drm_panel_get_orientation() to return panel
> >     orientation
> >   drm/panel: boe-tv101wum-nl6: Implement .get_orientation callback
> >   drm/panel: panel-edp: Implement .get_orientation callback
> >   drm/panel: lvds: Implement .get_orientation callback
> >   drm/panel: panel-simple: Implement .get_orientation callback
> >   drm/panel: ili9881c: Implement .get_orientation callback
> >   drm/panel: elida-kd35t133: Implement .get_orientation callback
> >   drm/mediatek: Config orientation property if panel provides it
> >
> >  drivers/gpu/drm/drm_panel.c                    |  8 ++++++++
> >  drivers/gpu/drm/mediatek/mtk_dsi.c             | 10 ++++++++++
> >  drivers/gpu/drm/panel/panel-boe-tv101wum-nl6.c |  8 ++++++++
> >  drivers/gpu/drm/panel/panel-edp.c              |  8 ++++++++
> >  drivers/gpu/drm/panel/panel-elida-kd35t133.c   |  8 ++++++++
> >  drivers/gpu/drm/panel/panel-ilitek-ili9881c.c  |  8 ++++++++
> >  drivers/gpu/drm/panel/panel-lvds.c             |  8 ++++++++
> >  drivers/gpu/drm/panel/panel-simple.c           |  9 +++++++++
> >  include/drm/drm_panel.h                        | 10 ++++++++++
> >  9 files changed, 77 insertions(+)
> >
>