Re: [Intel-gfx] [PATCH v6 3/7] drm/i915: Add checks specific to async flips

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Aug 07, 2020 at 03:05:47PM +0530, Karthik B S wrote:
> If flip is requested on any other plane, reject it.
> 
> Make sure there is no change in fbc, offset and framebuffer modifiers
> when async flip is requested.
> 
> If any of these are modified, reject async flip.
> 
> v2: -Replace DRM_ERROR (Paulo)
>     -Add check for changes in OFFSET, FBC, RC(Paulo)
> 
> v3: -Removed TODO as benchmarking tests have been run now.
> 
> v4: -Added more state checks for async flip (Ville)
>     -Moved intel_atomic_check_async to the end of intel_atomic_check
>      as the plane checks needs to pass before this. (Ville)
>     -Removed crtc_state->enable_fbc check. (Ville)
>     -Set the I915_MODE_FLAG_GET_SCANLINE_FROM_TIMESTAMP flag for async
>      flip case as scanline counter is not reliable here.
> 
> v5: -Fix typo and other check patch errors seen in CI
>      in 'intel_atomic_check_async' function.
> 
> v6: -Don't call intel_atomic_check_async multiple times. (Ville)
>     -Remove the check for n_planes in intel_atomic_check_async
>     -Added documentation for async flips. (Paulo)
> 
> Signed-off-by: Karthik B S <karthik.b.s@intel.com>
> Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 113 +++++++++++++++++++
>  1 file changed, 113 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index ce2b0c14a073..9629c751d2af 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -14832,6 +14832,110 @@ static bool intel_cpu_transcoders_need_modeset(struct intel_atomic_state *state,
>  	return false;
>  }
>  
> +/**
> + * DOC: asynchronous flip implementation
> + *
> + * Asynchronous page flip is the implementation for the DRM_MODE_PAGE_FLIP_ASYNC
> + * flag. Currently async flip is only supported via the drmModePageFlip IOCTL.
> + * Correspondingly, support is currently added for primary plane only.
> + *
> + * Async flip can only change the plane surface address, so anything else
> + * changing is rejected from the intel_atomic_check_async() function.
> + * Once this check is cleared, flip done interrupt is enabled using
> + * the skl_enable_flip_done() function.
> + *
> + * As soon as the surface address register is written, flip done interrupt is
> + * generated and the requested events are sent to the usersapce in the interrupt
> + * handler itself. The timestamp and sequence sent during the flip done event
> + * correspond to the last vblank and have no relation to the actual time when
> + * the flip done event was sent.
> + */
> +
> +static int intel_atomic_check_async(struct intel_atomic_state *state)
> +{
> +	struct intel_crtc_state *old_crtc_state, *new_crtc_state;
> +	struct intel_plane_state *new_plane_state, *old_plane_state;
> +	struct intel_crtc *crtc;
> +	struct intel_plane *intel_plane;

s/intel_plane/plane/

> +	int i;
> +
> +	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
> +					    new_crtc_state, i) {
> +		if (needs_modeset(new_crtc_state)) {
> +			DRM_DEBUG_KMS("Modeset Required. Async flip not supported\n");
> +			return -EINVAL;
> +		}
> +
> +		if (!new_crtc_state->uapi.active) {
> +			DRM_DEBUG_KMS("CRTC inactive\n");
> +			return -EINVAL;
> +		}

All the uapi.foo stuff should be hw.foo most likely.

> +		if (old_crtc_state->active_planes != new_crtc_state->active_planes) {
> +			DRM_DEBUG_KMS("Active planes cannot be changed during async flip\n");
> +			return -EINVAL;
> +		}
> +	}
> +
> +	for_each_oldnew_intel_plane_in_state(state, intel_plane, old_plane_state,
> +					     new_plane_state, i) {
> +		/*TODO: Async flip is only supported through the page flip IOCTL
> +		 * as of now. So support currently added for primary plane only.
> +		 * Support for other planes should be added when async flip is
> +		 * enabled in the atomic IOCTL path.
> +		 */
> +		if (intel_plane->id != PLANE_PRIMARY)
> +			return -EINVAL;
> +
> +		if (old_plane_state->color_plane[0].x !=
> +		    new_plane_state->color_plane[0].x ||
> +		    old_plane_state->color_plane[0].y !=
> +		    new_plane_state->color_plane[0].y) {
> +			DRM_DEBUG_KMS("Offsets cannot be changed in async flip\n");
> +			return -EINVAL;
> +		}
> +
> +		if (old_plane_state->uapi.fb->modifier !=
> +		    new_plane_state->uapi.fb->modifier) {
> +			DRM_DEBUG_KMS("Framebuffer modifiers cannot be changed in async flip\n");
> +			return -EINVAL;
> +		}
> +
> +		if (old_plane_state->uapi.fb->format !=
> +		    new_plane_state->uapi.fb->format) {
> +			DRM_DEBUG_KMS("Framebuffer format cannot be changed in async flip\n");
> +			return -EINVAL;
> +		}
> +
> +		if (intel_wm_need_update(old_plane_state, new_plane_state)) {

That function is meant for pre-g4x wm hacks only. Do not use.

> +			DRM_DEBUG_KMS("WM update not allowed in async flip\n");
> +			return -EINVAL;
> +		}
> +
> +		if (old_plane_state->uapi.alpha != new_plane_state->uapi.alpha) {
> +			DRM_DEBUG_KMS("Alpha value cannot be changed in async flip\n");
> +			return -EINVAL;
> +		}
> +
> +		if (old_plane_state->uapi.pixel_blend_mode !=
> +		    new_plane_state->uapi.pixel_blend_mode) {
> +			DRM_DEBUG_KMS("Pixel blend mode cannot be changed in async flip\n");
> +			return -EINVAL;
> +		}
> +
> +		if (old_plane_state->uapi.color_encoding != new_plane_state->uapi.color_encoding) {
> +			DRM_DEBUG_KMS("Color encoding cannot be changed in async flip\n");
> +			return -EINVAL;
> +		}
> +
> +		if (old_plane_state->uapi.color_range != new_plane_state->uapi.color_range) {
> +			DRM_DEBUG_KMS("Color range cannot be changed in async flip\n");
> +			return -EINVAL;
> +		}

Seems to be missing at least a dst coordinate check.

Not sure we can allow async flip with linear buffers. Older hw at least
had issues with that.

> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * intel_atomic_check - validate state object
>   * @dev: drm device
> @@ -15011,6 +15115,15 @@ static int intel_atomic_check(struct drm_device *dev,
>  				       "[modeset]" : "[fastset]");
>  	}
>  
> +	for_each_new_intel_crtc_in_state(state, crtc, new_crtc_state, i) {
> +		if (new_crtc_state->uapi.async_flip) {
> +			ret = intel_atomic_check_async(state);
> +			if (ret)
> +				goto fail;
> +
> +			break;

Why would we break here?

> +		}
> +	}
>  	return 0;
>  
>   fail:
> -- 
> 2.22.0

-- 
Ville Syrjälä
Intel
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