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

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Message-ID: <c890efc4-dfda-cab1-8a46-527e3e02168a@redhat.com>
Date:   Wed, 1 Jun 2022 10:57:04 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Hsin-Yi Wang <hsinyi@...omium.org>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>
Cc:     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

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.






> @@ -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;

?

Note -ENODEV is probably not the right error the check for!

Regards,

Hans



>  	ret = mtk_dsi_encoder_init(drm, dsi);
>  	if (ret)
>  		return ret;