Re: [PATCH] drm/mediatek: Ensure the cursor plane is on top of other overlays

From: Sean Paul <sean@poorly.run>
To: evanbenn@google.com
Cc: dcastagna@chromium.org, evanbenn@gmail.com,
	evanbenn@chromium.org, dri-devel@lists.freedesktop.org,
	matthias.bgg@gmail.com, linux-mediatek@lists.infradead.org,
	p.zabel@pengutronix.de, ck.hu@mediatek.com,
	seanpaul@chromium.org, sean@poorly.run,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] drm/mediatek: Ensure the cursor plane is on top of other overlays
Date: Thu, 6 Feb 2020 09:01:40 -0500	[thread overview]
Message-ID: <20200206140140.GA18465@art_vandelay> (raw)
In-Reply-To: <20200206065951.213862-1-evanbenn@google.com>

On Thu, Feb 06, 2020 at 05:59:51PM +1100, evanbenn@google.com wrote:
> From: Sean Paul <seanpaul@chromium.org>
> 
> Currently the cursor is placed on the first overlay plane, which means
> it will be at the bottom of the stack when the hw does the compositing
> with anything other than primary plane. Since mtk doesn't support plane
> zpos, change the cursor location to the top-most plane.
> 
> Signed-off-by: Evan Benn <evanbenn@chromium.org>

Hi Evan,
Thanks for spotting the issue! I think this should probably be 2 patches, one to
fix crtc init and then the cursor patch on top of that. We generally try to only
do one thing per patch.

A few other nits below..

> Signed-off-by: Sean Paul <seanpaul@chromium.org>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 29 +++++++++++++++++--------
>  1 file changed, 20 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index 7b392d6c71cc..d4078c2089e0 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -658,10 +658,21 @@ static const struct drm_crtc_helper_funcs mtk_crtc_helper_funcs = {
>  
>  static int mtk_drm_crtc_init(struct drm_device *drm,
>  			     struct mtk_drm_crtc *mtk_crtc,
> -			     struct drm_plane *primary,
> -			     struct drm_plane *cursor, unsigned int pipe)
> +			     unsigned int pipe)
>  {
> -	int ret;
> +	int i, ret;
> +

extra line

> +	struct drm_plane *primary = NULL;
> +	struct drm_plane *cursor = NULL;

These should be on top of the int declaration

> +
> +	for (i = 0; i < mtk_crtc->layer_nr; ++i) {

We don't really do pre-increment in kernel for loops

> +		if (!primary && mtk_crtc->planes[i].type ==
> +				DRM_PLANE_TYPE_PRIMARY)

Line breaks should be around '&&':

                if (!primary &&
                    mtk_crtc->planes[i].type == DRM_PLANE_TYPE_PRIMARY)

> +			primary = &mtk_crtc->planes[i];
> +		if (!cursor && mtk_crtc->planes[i].type ==

else if?

> +				DRM_PLANE_TYPE_CURSOR)
> +			cursor = &mtk_crtc->planes[i];

Since we can only have one primary and one cursor, the NULL checks on primary
and cursor are unnecessary, you can just blindly assign them when you hit a
plane of the right type. If the driver creates multiples the behavior is
undefined anyways.

> +	}
>  
>  	ret = drm_crtc_init_with_planes(drm, &mtk_crtc->base, primary, cursor,
>  					&mtk_crtc_funcs, NULL);
> @@ -711,11 +722,12 @@ static int mtk_drm_crtc_num_comp_planes(struct mtk_drm_crtc *mtk_crtc,
>  }
>  
>  static inline
> -enum drm_plane_type mtk_drm_crtc_plane_type(unsigned int plane_idx)
> +enum drm_plane_type mtk_drm_crtc_plane_type(unsigned int plane_idx,
> +					    unsigned int num_planes)
>  {
>  	if (plane_idx == 0)
>  		return DRM_PLANE_TYPE_PRIMARY;
> -	else if (plane_idx == 1)
> +	else if (plane_idx == (num_planes - 1))
>  		return DRM_PLANE_TYPE_CURSOR;
>  	else
>  		return DRM_PLANE_TYPE_OVERLAY;
> @@ -734,7 +746,8 @@ static int mtk_drm_crtc_init_comp_planes(struct drm_device *drm_dev,
>  		ret = mtk_plane_init(drm_dev,
>  				&mtk_crtc->planes[mtk_crtc->layer_nr],
>  				BIT(pipe),
> -				mtk_drm_crtc_plane_type(mtk_crtc->layer_nr),
> +				mtk_drm_crtc_plane_type(mtk_crtc->layer_nr,
> +							num_planes),
>  				mtk_ddp_comp_supported_rotations(comp));
>  		if (ret)
>  			return ret;
> @@ -830,9 +843,7 @@ int mtk_drm_crtc_create(struct drm_device *drm_dev,
>  			return ret;
>  	}
>  
> -	ret = mtk_drm_crtc_init(drm_dev, mtk_crtc, &mtk_crtc->planes[0],
> -				mtk_crtc->layer_nr > 1 ? &mtk_crtc->planes[1] :
> -				NULL, pipe);
> +	ret = mtk_drm_crtc_init(drm_dev, mtk_crtc, pipe);
>  	if (ret < 0)
>  		return ret;
>  
> -- 
> 2.25.0.341.g760bfbb309-goog
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS

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