Re: [Intel-gfx] [PATCH v2 9/9] drm/i915: Add "maximum pipe read bandwidth" checks

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Thu, Mar 03, 2022 at 09:12:07PM +0200, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> Make sure the CDCLK is high enough to support the so called
> "maximum pipe read bandwidth" limitation. Specified as
> 51.2 x CDCLK.

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>

> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bw.c | 36 +++++++++++++++++++++----
>  drivers/gpu/drm/i915/display/intel_bw.h |  1 +
>  2 files changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
> index ed86f3e3c66c..e5e772c4fcfb 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.c
> +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> @@ -599,6 +599,18 @@ static unsigned int intel_bw_crtc_data_rate(const struct intel_crtc_state *crtc_
>  	return data_rate;
>  }
>  
> +/* "Maximum Pipe Read Bandwidth" */
> +static int intel_bw_crtc_min_cdclk(const struct intel_crtc_state *crtc_state)
> +{
> +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> +	struct drm_i915_private *i915 = to_i915(crtc->base.dev);
> +
> +	if (DISPLAY_VER(i915) < 12)
> +		return 0;
> +
> +	return DIV_ROUND_UP_ULL(mul_u32_u32(intel_bw_crtc_data_rate(crtc_state), 10), 512);
> +}
> +
>  void intel_bw_crtc_update(struct intel_bw_state *bw_state,
>  			  const struct intel_crtc_state *crtc_state)
>  {
> @@ -696,6 +708,9 @@ static bool intel_bw_state_changed(struct drm_i915_private *i915,
>  			    old_crtc_bw->active_planes[slice] != new_crtc_bw->active_planes[slice])
>  				return true;
>  		}
> +
> +		if (old_bw_state->min_cdclk[pipe] != new_bw_state->min_cdclk[pipe])
> +			return true;
>  	}
>  
>  	return false;
> @@ -788,7 +803,15 @@ intel_bw_dbuf_min_cdclk(struct drm_i915_private *i915,
>  int intel_bw_min_cdclk(struct drm_i915_private *i915,
>  		       const struct intel_bw_state *bw_state)
>  {
> -	return intel_bw_dbuf_min_cdclk(i915, bw_state);
> +	enum pipe pipe;
> +	int min_cdclk;
> +
> +	min_cdclk = intel_bw_dbuf_min_cdclk(i915, bw_state);
> +
> +	for_each_pipe(i915, pipe)
> +		min_cdclk = max(bw_state->min_cdclk[pipe], min_cdclk);
> +
> +	return min_cdclk;
>  }
>  
>  int intel_bw_calc_min_cdclk(struct intel_atomic_state *state,
> @@ -814,6 +837,9 @@ int intel_bw_calc_min_cdclk(struct intel_atomic_state *state,
>  		old_bw_state = intel_atomic_get_old_bw_state(state);
>  
>  		skl_crtc_calc_dbuf_bw(new_bw_state, crtc_state);
> +
> +		new_bw_state->min_cdclk[crtc->pipe] =
> +			intel_bw_crtc_min_cdclk(crtc_state);
>  	}
>  
>  	if (!old_bw_state)
> @@ -830,9 +856,9 @@ int intel_bw_calc_min_cdclk(struct intel_atomic_state *state,
>  
>  	/*
>  	 * No need to check against the cdclk state if
> -	 * the min cdclk for the dbuf doesn't increase.
> +	 * the min cdclk doesn't increase.
>  	 *
> -	 * Ie. we only ever increase the cdclk due to dbuf
> +	 * Ie. we only ever increase the cdclk due to bandwidth
>  	 * requirements. This can reduce back and forth
>  	 * display blinking due to constant cdclk changes.
>  	 */
> @@ -845,9 +871,9 @@ int intel_bw_calc_min_cdclk(struct intel_atomic_state *state,
>  
>  	/*
>  	 * No need to recalculate the cdclk state if
> -	 * the min cdclk for the dbuf doesn't increase.
> +	 * the min cdclk doesn't increase.
>  	 *
> -	 * Ie. we only ever increase the cdclk due to dbuf
> +	 * Ie. we only ever increase the cdclk due to bandwidth
>  	 * requirements. This can reduce back and forth
>  	 * display blinking due to constant cdclk changes.
>  	 */
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.h b/drivers/gpu/drm/i915/display/intel_bw.h
> index 92fc09a8c824..cb7ee3a24a58 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.h
> +++ b/drivers/gpu/drm/i915/display/intel_bw.h
> @@ -41,6 +41,7 @@ struct intel_bw_state {
>  	 */
>  	u16 qgv_points_mask;
>  
> +	int min_cdclk[I915_MAX_PIPES];
>  	unsigned int data_rate[I915_MAX_PIPES];
>  	u8 num_active_planes[I915_MAX_PIPES];
>  };
> -- 
> 2.34.1
>