Re: [Intel-gfx] [PATCH v2] drm/i915: implement async_flip mode per plane tracking

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

On Wed, Jan 11, 2023 at 05:22:47PM +0100, Andrzej Hajda wrote:
> Current implementation of async flip w/a relies on assumption that
> previous atomic commit contains valid information if async_flip is still
> enabled on the plane. It is incorrect. If previous commit did not modify
> the plane its state->uapi.async_flip can be false. As a result DMAR/PIPE
> errors can be observed:
> i915 0000:00:02.0: [drm] *ERROR* Fault errors on pipe A: 0x00000080
> i915 0000:00:02.0: [drm] *ERROR* Fault errors on pipe A: 0x00000080
> DMAR: DRHD: handling fault status reg 2
> DMAR: [DMA Read NO_PASID] Request device [00:02.0] fault addr 0x0 [fault reason 0x06] PTE Read access is not set
> 
> v2: update async_flip_planes in more reliable places (Ville)
> 
> Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_atomic_plane.c  | 5 ++++-
>  drivers/gpu/drm/i915/display/intel_display.c       | 7 ++++---
>  drivers/gpu/drm/i915/display/intel_display_types.h | 3 +++
>  3 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> index 10e1fc9d069827..3f1b1548ede025 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> +++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> @@ -362,6 +362,7 @@ void intel_plane_set_invisible(struct intel_crtc_state *crtc_state,
>  	crtc_state->scaled_planes &= ~BIT(plane->id);
>  	crtc_state->nv12_planes &= ~BIT(plane->id);
>  	crtc_state->c8_planes &= ~BIT(plane->id);
> +	crtc_state->async_flip_planes &= ~BIT(plane->id);
>  	crtc_state->data_rate[plane->id] = 0;
>  	crtc_state->data_rate_y[plane->id] = 0;
>  	crtc_state->rel_data_rate[plane->id] = 0;
> @@ -581,8 +582,10 @@ static int intel_plane_atomic_calc_changes(const struct intel_crtc_state *old_cr
>  			 intel_plane_is_scaled(new_plane_state))))
>  		new_crtc_state->disable_lp_wm = true;
>  
> -	if (intel_plane_do_async_flip(plane, old_crtc_state, new_crtc_state))
> +	if (intel_plane_do_async_flip(plane, old_crtc_state, new_crtc_state)) {
>  		new_crtc_state->do_async_flip = true;
> +		new_crtc_state->async_flip_planes |= BIT(plane->id);
> +	}

intel_modeset_all_pipes() and intel_color_add_affected_planes() would
need to clear this stuff as well. Can't immediately think of other
places that need the same treatment (the nv12 plane stuff I believe
should be fine without this since we should be rejecting async flips
with planar formats).

Though I think that is still going to have annoying ping-pong 
for the the wm/ddb optimizations whenever there are internal
sync plane updates injected between async flips. I think to
sort that out fully we'd need to start tracking the last uapi
async flip state for each plane.

>  
>  	return 0;
>  }
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index e75b9b2a0e015a..e1c3b1b0b6a8f1 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -1303,7 +1303,8 @@ static void intel_crtc_async_flip_disable_wa(struct intel_atomic_state *state,
>  		intel_atomic_get_old_crtc_state(state, crtc);
>  	const struct intel_crtc_state *new_crtc_state =
>  		intel_atomic_get_new_crtc_state(state, crtc);
> -	u8 update_planes = new_crtc_state->update_planes;
> +	u8 disable_async_flip_planes = old_crtc_state->async_flip_planes &
> +				       ~new_crtc_state->async_flip_planes;
>  	const struct intel_plane_state *old_plane_state;
>  	struct intel_plane *plane;
>  	bool need_vbl_wait = false;
> @@ -1312,7 +1313,7 @@ static void intel_crtc_async_flip_disable_wa(struct intel_atomic_state *state,
>  	for_each_old_intel_plane_in_state(state, plane, old_plane_state, i) {
>  		if (plane->need_async_flip_disable_wa &&
>  		    plane->pipe == crtc->pipe &&
> -		    update_planes & BIT(plane->id)) {
> +		    disable_async_flip_planes & BIT(plane->id)) {
>  			/*
>  			 * Apart from the async flip bit we want to
>  			 * preserve the old state for the plane.
> @@ -1429,7 +1430,7 @@ static void intel_pre_plane_update(struct intel_atomic_state *state,
>  	 * WA for platforms where async address update enable bit
>  	 * is double buffered and only latched at start of vblank.
>  	 */
> -	if (old_crtc_state->uapi.async_flip && !new_crtc_state->uapi.async_flip)
> +	if (old_crtc_state->async_flip_planes & ~new_crtc_state->async_flip_planes)
>  		intel_crtc_async_flip_disable_wa(state, crtc);
>  }
>  
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 32e8b2fc3cc642..61b1a0ec3dede1 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1248,6 +1248,9 @@ struct intel_crtc_state {
>  	/* bitmask of planes that will be updated during the commit */
>  	u8 update_planes;
>  
> +	/* bitmask of planes with async flip active */
> +	u8 async_flip_planes;
> +
>  	u8 framestart_delay; /* 1-4 */
>  	u8 msa_timing_delay; /* 0-3 */
>  
> -- 
> 2.34.1

-- 
Ville Syrjälä
Intel