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

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Date:   Mon, 14 Feb 2022 20:16:56 -0500
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Hsin-Yi Wang <hsinyi@...omium.org>
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

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
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