Re: [Intel-gfx] [PATCH] drm/i915: Recalculate CDCLK if plane scaling ratio changes

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 11 Jan 2022, Stanislav Lisovskiy <stanislav.lisovskiy@intel.com> wrote:
> Currently we only recalculate CDCLK if active plane mask changes
> or if we do a full modeset, however according to BSpec
> required Dbuf bandwidth calculations also depend on pipe/plane
> scaling ratio, which means that CDCLK must be recalculated
> everytime plane scaling ratio changes, because it affects
> display buffer bandwidth requirements.
>
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 63 +++++++++++++++++++-
>  1 file changed, 60 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index bf7ce684dd8e..2c616348e993 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -7499,13 +7499,65 @@ static int intel_bigjoiner_add_affected_planes(struct intel_atomic_state *state)
>  	return 0;
>  }
>  
> +static bool scaling_affects_cdclk(struct intel_plane_state *old_plane_state,
> +				  struct intel_plane_state *new_plane_state)
> +{
> +	int old_src_w = drm_rect_width(&old_plane_state->uapi.src) >> 16;
> +	int old_src_h = drm_rect_height(&old_plane_state->uapi.src) >> 16;
> +	int old_dst_w = drm_rect_width(&old_plane_state->uapi.dst);
> +	int old_dst_h = drm_rect_height(&old_plane_state->uapi.dst);
> +	int new_src_w = drm_rect_width(&new_plane_state->uapi.src) >> 16;
> +	int new_src_h = drm_rect_height(&new_plane_state->uapi.src) >> 16;
> +	int new_dst_w = drm_rect_width(&new_plane_state->uapi.dst);
> +	int new_dst_h = drm_rect_height(&new_plane_state->uapi.dst);
> +	int old_hscale_ratio, new_hscale_ratio;
> +	int old_vscale_ratio, new_vscale_ratio;
> +
> +	if (needs_scaling(old_plane_state) != needs_scaling(new_plane_state))
> +		return true;
> +
> +	if (!old_dst_w || !old_dst_h)
> +		return true;
> +
> +	DRM_DEBUG_KMS("old_dst_w %d old_dst_h %d\n", old_dst_w, old_dst_h);
> +
> +	old_hscale_ratio = DIV_ROUND_UP(old_src_w, old_dst_w);
> +	old_vscale_ratio = DIV_ROUND_UP(old_src_h, old_dst_h);
> +
> +	if (!new_dst_w || !new_dst_h)
> +		return true;
> +
> +	DRM_DEBUG_KMS("new_dst_w %d new_dst_h %d\n", new_dst_w, new_dst_h);
> +
> +	new_hscale_ratio = DIV_ROUND_UP(new_src_w, new_dst_w);
> +	new_vscale_ratio = DIV_ROUND_UP(new_src_h, new_dst_h);
> +
> +	DRM_DEBUG_KMS("new_hscale_ratio %d new_vscale_ratio %d "
> +		      "old_hscale_ratio %d old_vscale_ratio %d\n",
> +		      new_hscale_ratio, new_vscale_ratio,
> +		      old_hscale_ratio, old_vscale_ratio);

All of the debug logging seem excessive? Also, please use drm_dbg_atomic
or drm_dbg_kms instead of DRM_DEBUG_KMS for the ones that need to stay.

BR,
Jani.

> +
> +	if ((old_hscale_ratio != new_hscale_ratio) ||
> +	    (old_vscale_ratio != new_vscale_ratio)) {
> +		DRM_DEBUG_KMS("Scaling ratios changed from %dx%d"
> +			      " to %dx%d - need cdclk recalc\n",
> +			      old_hscale_ratio, old_vscale_ratio,
> +			      new_hscale_ratio, new_vscale_ratio);
> +		return true;
> +	}
> +
> +	return false;
> +}
> +
>  static int intel_atomic_check_planes(struct intel_atomic_state *state)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(state->base.dev);
>  	struct intel_crtc_state *old_crtc_state, *new_crtc_state;
>  	struct intel_plane_state *plane_state;
> +	struct intel_plane_state *old_plane_state;
>  	struct intel_plane *plane;
>  	struct intel_crtc *crtc;
> +	bool need_cdclk_calc = false;
>  	int i, ret;
>  
>  	ret = icl_add_linked_planes(state);
> @@ -7516,7 +7568,7 @@ static int intel_atomic_check_planes(struct intel_atomic_state *state)
>  	if (ret)
>  		return ret;
>  
> -	for_each_new_intel_plane_in_state(state, plane, plane_state, i) {
> +	for_each_oldnew_intel_plane_in_state(state, plane, old_plane_state, plane_state, i) {
>  		ret = intel_plane_atomic_check(state, plane);
>  		if (ret) {
>  			drm_dbg_atomic(&dev_priv->drm,
> @@ -7524,6 +7576,9 @@ static int intel_atomic_check_planes(struct intel_atomic_state *state)
>  				       plane->base.base.id, plane->base.name);
>  			return ret;
>  		}
> +
> +		if (scaling_affects_cdclk(old_plane_state, plane_state))
> +			need_cdclk_calc = true;
>  	}
>  
>  	for_each_oldnew_intel_crtc_in_state(state, crtc, old_crtc_state,
> @@ -7539,18 +7594,20 @@ static int intel_atomic_check_planes(struct intel_atomic_state *state)
>  		 * the planes' minimum cdclk calculation. Add such planes
>  		 * to the state before we compute the minimum cdclk.
>  		 */
> -		if (!active_planes_affects_min_cdclk(dev_priv))
> +		if (!active_planes_affects_min_cdclk(dev_priv) && !need_cdclk_calc)
>  			continue;
>  
>  		old_active_planes = old_crtc_state->active_planes & ~BIT(PLANE_CURSOR);
>  		new_active_planes = new_crtc_state->active_planes & ~BIT(PLANE_CURSOR);
>  
> -		if (hweight8(old_active_planes) == hweight8(new_active_planes))
> +		if ((hweight8(old_active_planes) == hweight8(new_active_planes)) && !need_cdclk_calc)
>  			continue;
>  
>  		ret = intel_crtc_add_planes_to_state(state, crtc, new_active_planes);
>  		if (ret)
>  			return ret;
> +
> +
>  	}
>  
>  	return 0;

-- 
Jani Nikula, Intel Open Source Graphics Center