linux-kernel - Re: [PATCH v8 1/3] gpu: drm: separate panel orientation property creating and value setting

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Message-ID: <CAJMQK-igpiYj-pkgG9amrQuVzf1Mc9BDDOwOdKLUbceKr=CHiQ@mail.gmail.com>
Date:   Tue, 15 Feb 2022 11:15:02 +0800
From:   Hsin-Yi Wang <hsinyi@...omium.org>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Sean Paul <sean@...rly.run>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Simon Ser <contact@...rsion.fr>,
        Harry Wentland <harry.wentland@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Jani Nikula <jani.nikula@...ux.intel.com>
Subject: Re: [PATCH v8 1/3] gpu: drm: separate panel orientation property
 creating and value setting

On Tue, Feb 15, 2022 at 9:17 AM Gabriel Krisman Bertazi
<krisman@...labora.com> wrote:
>
> Hsin-Yi Wang <hsinyi@...omium.org> writes:
>
> > drm_dev_register() sets connector->registration_state to
> > DRM_CONNECTOR_REGISTERED and dev->registered to true. If
> > drm_connector_set_panel_orientation() is first called after
> > drm_dev_register(), it will fail several checks and results in following
> > warning.
>
> Hi,
>
> I stumbled upon this when investigating the same WARN_ON on amdgpu.
> Thanks for the patch :)
>
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index a50c82bc2b2fec..572ead7ac10690 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -1252,7 +1252,7 @@ static const struct drm_prop_enum_list dp_colorspaces[] = {
> >   *   INPUT_PROP_DIRECT) will still map 1:1 to the actual LCD panel
> >   *   coordinates, so if userspace rotates the picture to adjust for
> >   *   the orientation it must also apply the same transformation to the
> > - *   touchscreen input coordinates. This property is initialized by calling
> > + *   touchscreen input coordinates. This property value is set by calling
> >   *   drm_connector_set_panel_orientation() or
> >   *   drm_connector_set_panel_orientation_with_quirk()
> >   *
> > @@ -2341,8 +2341,8 @@ EXPORT_SYMBOL(drm_connector_set_vrr_capable_property);
> >   * @connector: connector for which to set the panel-orientation property.
> >   * @panel_orientation: drm_panel_orientation value to set
> >   *
> > - * This function sets the connector's panel_orientation and attaches
> > - * a "panel orientation" property to the connector.
> > + * This function sets the connector's panel_orientation value. If the property
> > + * doesn't exist, it will try to create one.
> >   *
> >   * Calling this function on a connector where the panel_orientation has
> >   * already been set is a no-op (e.g. the orientation has been overridden with
> > @@ -2373,19 +2373,12 @@ int drm_connector_set_panel_orientation(
> >       info->panel_orientation = panel_orientation;
> >
> >       prop = dev->mode_config.panel_orientation_property;
> > -     if (!prop) {
> > -             prop = drm_property_create_enum(dev, DRM_MODE_PROP_IMMUTABLE,
> > -                             "panel orientation",
> > -                             drm_panel_orientation_enum_list,
> > -                             ARRAY_SIZE(drm_panel_orientation_enum_list));
> > -             if (!prop)
> > -                     return -ENOMEM;
> > -
> > -             dev->mode_config.panel_orientation_property = prop;
> > -     }
> > +     if (!prop &&
> > +         drm_connector_init_panel_orientation_property(connector) < 0)
> > +             return -ENOMEM;
> >
>
> In the case where the property has not been created beforehand, you
> forgot to reinitialize prop here, after calling
> drm_connector_init_panel_orientation_property().  This means
hi Gabriel,

drm_connector_init_panel_orientation_property() will create prop if
it's null. If prop fails to be created there, it will return -ENOMEM.

> drm_object_property_set_value() will be called with a NULL second argument
> and Oops the kernel.
>
>
> > -     drm_object_attach_property(&connector->base, prop,
> > -                                info->panel_orientation);
> > +     drm_object_property_set_value(&connector->base, prop,
> > +                                   info->panel_orientation);
>
>
> --
> Gabriel Krisman Bertazi