Re: [Intel-gfx] [PATCH 4/4] drm/i915: Don't allocate extra ddb during async flip for DG2

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

On Fri, Dec 03, 2021 at 11:40:41AM +0200, Stanislav Lisovskiy wrote:
> In terms of async flip optimization we don't to allocate
> extra ddb space, so lets skip it.
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 24 ++++++++++++++++++------
>  1 file changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 0b45d1d61d0f..e1594f43bb1b 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -5245,9 +5245,15 @@ skl_allocate_plane_ddb(struct intel_atomic_state *state,
>  			break;
>  
>  		rate = crtc_state->plane_data_rate[plane_id];
> -		extra = min_t(u16, alloc_size,
> -			      DIV64_U64_ROUND_UP(alloc_size * rate,
> -						 total_data_rate));
> +
> +		if (IS_DG2(dev_priv) && crtc_state->uapi.async_flip) {

We should have a sensible function for this.

> +			extra = 0;

Aren't we going to get the WARN(alloc_size != 0) if this
is the only enabled plane?

> +		} else {
> +			extra = min_t(u16, alloc_size,
> +				      DIV64_U64_ROUND_UP(alloc_size * rate,
> +							 total_data_rate));
> +		}
> +
>  		total[plane_id] = wm->wm[level].min_ddb_alloc + extra;
>  		alloc_size -= extra;
>  		total_data_rate -= rate;
> @@ -5256,9 +5262,15 @@ skl_allocate_plane_ddb(struct intel_atomic_state *state,
>  			break;
>  
>  		rate = crtc_state->uv_plane_data_rate[plane_id];
> -		extra = min_t(u16, alloc_size,
> -			      DIV64_U64_ROUND_UP(alloc_size * rate,
> -						 total_data_rate));
> +
> +		if (IS_DG2(dev_priv) && crtc_state->uapi.async_flip) {
> +			extra = 0;
> +		} else {
> +			extra = min_t(u16, alloc_size,
> +				      DIV64_U64_ROUND_UP(alloc_size * rate,
> +							 total_data_rate));
> +		}
> +
>  		uv_total[plane_id] = wm->uv_wm[level].min_ddb_alloc + extra;
>  		alloc_size -= extra;
>  		total_data_rate -= rate;
> -- 
> 2.24.1.485.gad05a3d8e5

-- 
Ville Syrjälä
Intel