linux-kernel - Re: [PATCH 8/8] drm/mediatek: Config orientation property if panel provides it

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Date:   Wed, 1 Jun 2022 17:29:58 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        Rob Clark <robdclark@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 8/8] drm/mediatek: Config orientation property if panel
 provides it

On Wed, Jun 1, 2022 at 4:57 PM Hans de Goede <hdegoede@...hat.com> wrote:
>
> Hi,
>
> On 6/1/22 10:18, Hsin-Yi Wang wrote:
> > Panel orientation property should be set before drm_dev_register().
> > Mediatek drm driver calls drm_dev_register() in .bind(). However, most
> > panels sets orientation property relatively late, mostly in .get_modes()
> > callback, since this is when they are able to get the connector and
> > binds the orientation property to it, though the value should be known
> > when the panel is probed.
> >
> > Let the drm driver check if the remote end point is a panel and if it
> > contains the orientation property. If it does, set it before
> > drm_dev_register() is called.
> >
> > Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
> > ---
> > The concept is the same as the previous version.
> > https://patchwork.kernel.org/project/linux-mediatek/patch/20220530113033.124072-1-hsinyi@chromium.org/
> > The only difference is, it now uses the panel API instead of parsing
> > orientation from the driver.
> > ---
> >  drivers/gpu/drm/mediatek/mtk_dsi.c | 14 ++++++++++++++
> >  1 file changed, 14 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dsi.c b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > index bd3f5b485085..12836a697f56 100644
> > --- a/drivers/gpu/drm/mediatek/mtk_dsi.c
> > +++ b/drivers/gpu/drm/mediatek/mtk_dsi.c
> > @@ -185,6 +185,7 @@ struct mtk_dsi {
> >       struct drm_encoder encoder;
> >       struct drm_bridge bridge;
> >       struct drm_bridge *next_bridge;
> > +     struct drm_panel *panel;
> >       struct drm_connector *connector;
> >       struct phy *phy;
> >
> > @@ -822,6 +823,16 @@ static int mtk_dsi_encoder_init(struct drm_device *drm, struct mtk_dsi *dsi)
> >               ret = PTR_ERR(dsi->connector);
> >               goto err_cleanup_encoder;
> >       }
> > +
> > +     /* Read panel orientation */
> > +     if (dsi->panel) {
> > +             enum drm_panel_orientation orientation;
> > +
> > +             orientation = drm_panel_get_orientation(dsi->panel);
> > +             if (orientation != DRM_MODE_PANEL_ORIENTATION_UNKNOWN)
> > +                     drm_connector_set_panel_orientation(dsi->connector, orientation);
> > +     }
> > +
> >       drm_connector_attach_encoder(dsi->connector, &dsi->encoder);
> >
> >       return 0;
>
> drm_connector_set_panel_orientation() is a no-op when called with
> DRM_MODE_PANEL_ORIENTATION_UNKNOWN, so the check for this is not
> necessary. This allows this to be simplified to:
>
>         /* Read panel orientation */
>         if (dsi->panel)
>                 drm_connector_set_panel_orientation(dsi->connector,
>                                                     drm_panel_get_orientation(dsi->panel));
>
>
> Note since drm_panel_get_orientation() checks for a NULL panel, you could even
> drop the "if (dsi->panel)", but I think the meaning of the code is more
> clear with that present.
>
Will update this
>
>
>
>
>
> > @@ -837,6 +848,9 @@ static int mtk_dsi_bind(struct device *dev, struct device *master, void *data)
> >       struct drm_device *drm = data;
> >       struct mtk_dsi *dsi = dev_get_drvdata(dev);
> >
> > +     /* Get panel if existed */
> > +     ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0, &dsi->panel, NULL);
> > +
>
> Check ret? or maybe not assign to ret ?    I understand some errors are expected
> so maybe something like:
>
>         if (ret && ret != -ENODEV)
>                 return ret;
>
I will choose not to assign ret. In some cases that the end point is a
bridge (not panel), since we assign NULL to the bridge, we will get
EPROBE_DEFER.

If the panel fails at this stage,
drm_connector_set_panel_orientation() is just a no-op. Let dsi still
be able to be binded.


> ?
>
> Note -ENODEV is probably not the right error the check for!
>
> Regards,
>
> Hans
>
>
>
> >       ret = mtk_dsi_encoder_init(drm, dsi);
> >       if (ret)
> >               return ret;
>