Re: [PATCH] drm/amd/display: ensure async flips are only accepted for fast updates

[Harry Wentland]

On 2023-08-04 11:56, Hamza Mahfooz wrote:
> We should be checking to see if async flips are supported in
> amdgpu_dm_atomic_check() (i.e. not dm_crtc_helper_atomic_check()). Also,
> async flipping isn't supported if a plane's framebuffer changes memory
> domains during an atomic commit. So, move the check from
> dm_crtc_helper_atomic_check() to amdgpu_dm_atomic_check() and check if
> the memory domain has changed in amdgpu_dm_atomic_check().
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 3f86b60691e6 ("drm/amd/display: only accept async flips for fast updates")
> Tested-by: Marcus Seyfarth <m.seyfarth@xxxxxxxxx>
> Signed-off-by: Hamza Mahfooz <hamza.mahfooz@xxxxxxx>
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 25 ++++++++++++++++---
>  .../amd/display/amdgpu_dm/amdgpu_dm_crtc.c    | 12 ---------
>  2 files changed, 21 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 32fb551862b0..e561d99b3f40 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -8086,7 +8086,8 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
>  		 * fast updates.
>  		 */
>  		if (crtc->state->async_flip &&
> -		    acrtc_state->update_type != UPDATE_TYPE_FAST)
> +		    (acrtc_state->update_type != UPDATE_TYPE_FAST ||
> +		     get_mem_type(old_plane_state->fb) != get_mem_type(fb)))
>  			drm_warn_once(state->dev,
>  				      "[PLANE:%d:%s] async flip with non-fast update\n",
>  				      plane->base.id, plane->name);
> @@ -10050,12 +10051,18 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
>  
>  	/* Remove exiting planes if they are modified */
>  	for_each_oldnew_plane_in_state_reverse(state, plane, old_plane_state, new_plane_state, i) {
> +		if (old_plane_state->fb && new_plane_state->fb &&
> +		    get_mem_type(old_plane_state->fb) !=
> +		    get_mem_type(new_plane_state->fb))
> +			lock_and_validation_needed = true;
> +
>  		ret = dm_update_plane_state(dc, state, plane,
>  					    old_plane_state,
>  					    new_plane_state,
>  					    false,
>  					    &lock_and_validation_needed,
>  					    &is_top_most_overlay);
> +

nit: extraneous newline

>  		if (ret) {
>  			DRM_DEBUG_DRIVER("dm_update_plane_state() failed\n");
>  			goto fail;
> @@ -10069,6 +10076,7 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
>  					   new_crtc_state,
>  					   false,
>  					   &lock_and_validation_needed);
> +

nit: extraneous newline

>  		if (ret) {
>  			DRM_DEBUG_DRIVER("DISABLE: dm_update_crtc_state() failed\n");
>  			goto fail;
> @@ -10297,9 +10305,18 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
>  		struct dm_crtc_state *dm_new_crtc_state =
>  			to_dm_crtc_state(new_crtc_state);
>  
> -		dm_new_crtc_state->update_type = lock_and_validation_needed ?
> -							 UPDATE_TYPE_FULL :
> -							 UPDATE_TYPE_FAST;
> +		/*
> +		 * Only allow async flips for fast updates that don't change
> +		 * the FB pitch, the DCC state, rotation, etc.
> +		 */
> +		if (new_crtc_state->async_flip && lock_and_validation_needed) {
> +			drm_dbg_atomic(crtc->dev,
> +				       "[CRTC:%d:%s] async flips are only supported for fast updates\n",
> +				       crtc->base.id, crtc->name);
> +			ret = -EINVAL;
> +			goto fail;
> +		} else

nit: Add braces here as well

> +			dm_new_crtc_state->update_type = UPDATE_TYPE_FAST;

If async_flip is false you'll be setting update_type to FAST here
uncoditionally.

You'll still need the lock_and_validation check here, i.e. this:

> 		dm_new_crtc_state->update_type = lock_and_validation_needed ?
> 							 UPDATE_TYPE_FULL :
> 							 UPDATE_TYPE_FAST;

Harry

>  	}
>  
>  	/* Must be success */
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
> index 30d4c6fd95f5..440fc0869a34 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_crtc.c
> @@ -398,18 +398,6 @@ static int dm_crtc_helper_atomic_check(struct drm_crtc *crtc,
>  		return -EINVAL;
>  	}
>  
> -	/*
> -	 * Only allow async flips for fast updates that don't change the FB
> -	 * pitch, the DCC state, rotation, etc.
> -	 */
> -	if (crtc_state->async_flip &&
> -	    dm_crtc_state->update_type != UPDATE_TYPE_FAST) {
> -		drm_dbg_atomic(crtc->dev,
> -			       "[CRTC:%d:%s] async flips are only supported for fast updates\n",
> -			       crtc->base.id, crtc->name);
> -		return -EINVAL;
> -	}
> -
>  	/* In some use cases, like reset, no stream is attached */
>  	if (!dm_crtc_state->stream)
>  		return 0;