[Intel-gfx] [RFC 4/7] drm/i915: Add checks specific to async flips

[Paulo Zanoni]

Em sex, 2020-03-06 às 17:09 +0530, Karthik B S escreveu:
> Support added only for async flips on primary plane.
> If flip is requested on any other plane, reject it.
> 
> Signed-off-by: Karthik B S <karthik.b.s at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 29 ++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 25fad5d01e67..a8de08c3773e 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -14732,6 +14732,31 @@ static bool intel_cpu_transcoders_need_modeset(struct intel_atomic_state *state,
>  	return false;
>  }
>  
> +static int intel_atomic_check_async(struct intel_atomic_state *state)
> +{
> +	struct drm_plane *plane;
> +	struct drm_plane_state *plane_state;
> +	struct intel_crtc_state *crtc_state;
> +	struct intel_crtc *crtc;
> +	int i, j;
> +
> +	/*FIXME: Async flip is only supported for primary plane currently
> +	 * Support for overlays to be added.
> +	 */
> +	for_each_new_intel_crtc_in_state(state, crtc, crtc_state, i) {
> +		if (crtc_state->uapi.async_flip) {
> +			for_each_new_plane_in_state(&state->base,
> +						    plane, plane_state, j) {
> +				if (plane->type != DRM_PLANE_TYPE_PRIMARY) {
> +					DRM_ERROR("Async flips is NOT supported for non-primary plane\n");

My understanding is that this is not a case of DRM_ERROR, since it's
just user space doing something it shouldn't.

Have we checked if xf86-video-modesetting or some other current user
space is going to try these calls on non-primary when async_flips are
enabled? Specifically, how does it react when it gets the EINVAL? We
should try to avoid the case where we release a Kernel that current
user space is not prepared for (even if it's not the Kernel's fault).


> +					return -EINVAL;
> +				}
> +			}
> +		}
> +	}
> +	return 0;
> +}
> +
>  /**
>   * intel_atomic_check - validate state object
>   * @dev: drm device
> @@ -14760,6 +14785,10 @@ static int intel_atomic_check(struct drm_device *dev,
>  	if (ret)
>  		goto fail;
>  
> +	ret = intel_atomic_check_async(state);
> +	if  (ret)
> +		goto fail;
> +
>  	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
>  					    new_crtc_state, i) {
>  		if (!needs_modeset(new_crtc_state)) {