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Date:   Mon, 22 Jun 2020 15:20:14 +0000
From:   Tomasz Figa <tfiga@chromium.org>
To:     Hsin-Yi Wang <hsinyi@chromium.org>
Cc:     linux-arm-kernel@lists.infradead.org,
        Chun-Kuang Hu <chunkuang.hu@kernel.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        dri-devel@lists.freedesktop.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        yongqiang.niu@mediatek.com
Subject: Re: [PATCH v2] drm/mediatek: check plane visibility in atomic_update
Message-ID: <20200622152014.GA260716@chromium.org>
References: <20200622150109.91205-1-hsinyi@chromium.org>
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In-Reply-To: <20200622150109.91205-1-hsinyi@chromium.org>
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Hi Hsin-Yi,

On Mon, Jun 22, 2020 at 11:01:09PM +0800, Hsin-Yi Wang wrote:
> Disable the plane if it's not visible. Otherwise mtk_ovl_layer_config()
> would proceed with invalid plane and we may see vblank timeout.
> 
> Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
> Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
> Reviewed-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>
> ---
> v2: Add fixes tag
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_plane.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 

Thank you for the patch. Please see my comments inline.

> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.c b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> index c2bd683a87c8..74dc71c7f3b6 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> @@ -164,6 +164,16 @@ static int mtk_plane_atomic_check(struct drm_plane *plane,
>  						   true, true);
>  }
>  
> +static void mtk_plane_atomic_disable(struct drm_plane *plane,
> +				     struct drm_plane_state *old_state)
> +{
> +	struct mtk_plane_state *state = to_mtk_plane_state(plane->state);
> +
> +	state->pending.enable = false;
> +	wmb(); /* Make sure the above parameter is set before update */
> +	state->pending.dirty = true;
> +}
> +
>  static void mtk_plane_atomic_update(struct drm_plane *plane,
>  				    struct drm_plane_state *old_state)
>  {
> @@ -178,6 +188,9 @@ static void mtk_plane_atomic_update(struct drm_plane *plane,
>  	if (!crtc || WARN_ON(!fb))
>  		return;
>  
> +	if (!plane->state->visible)
> +		return mtk_plane_atomic_disable(plane, old_state);

nit: Both this function and mtk_plane_atomic_disable() have the void return
type. Perhaps we should rather move the return, without a value, to a
separate statement?

Best regards,
Tomasz