Re: [PATCH v5 2/2] drm/mediatek: Fix iommu fault during crtc enabling

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

Hi, Jason:

On Wed, 2023-08-09 at 20:57 +0800, Jason-JH.Lin wrote:
> The difference between drm_atomic_helper_commit_tail() and
> drm_atomic_helper_commit_tail_rpm() is
> drm_atomic_helper_commit_tail() will commit plane first and
> then enable crtc, drm_atomic_helper_commit_tail_rpm() will
> enable crtc first and then commit plane.
> 
> Before mediatek-drm enables crtc, the power and clk required
> by OVL have not been turned on, so the commit plane cannot be
> committed before crtc is enabled. That means OVL layer should
> not be enabled before crtc is enabled.
> Therefore, the atomic_commit_tail of mediatek-drm is hooked with
> drm_atomic_helper_commit_tail_rpm().
> 
> Another reason is that the plane_state of drm_atomic_state is not
> synchronized with the plane_state stored in mtk_crtc during crtc
> enablng,
> so just set all planes to disabled.

Reviewed-by: CK Hu <ck.hu@mediatek.com>

> 
> Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC
> MT8173.")
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
> Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
> Reviewed-by: AngeloGioacchino Del Regno <
> angelogioacchino.delregno@collabora.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index d40142842f85..51d10e65004e 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -410,6 +410,9 @@ static int mtk_crtc_ddp_hw_init(struct
> mtk_drm_crtc *mtk_crtc)
>  		unsigned int local_layer;
>  
>  		plane_state = to_mtk_plane_state(plane->state);
> +
> +		/* should not enable layer before crtc enabled */
> +		plane_state->pending.enable = false;
>  		comp = mtk_drm_ddp_comp_for_plane(crtc, plane,
> &local_layer);
>  		if (comp)
>  			mtk_ddp_comp_layer_config(comp, local_layer,