Re: [PATCH v10 2/6] drm/i915/display: Extract code required to calculate max qgv/psf gv point

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

On Fri, Apr 05, 2024 at 02:35:29PM +0300, Vinod Govindapillai wrote:
> From: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> 
> We need that in order to force disable SAGV in next patch.
> Also it is beneficial to separate that code, as in majority cases,
> when SAGV is enabled, we don't even need those calculations.
> Also we probably need to determine max PSF GV point as well, however
> currently we don't do that when we disable SAGV, which might be
> actually causing some issues in that case.
> 
> v2: - Introduce helper adl_qgv_bw(counterpart to adl_psf_bw)
>       (Ville Syrjälä)
>     - Don't restrict psf gv points for SAGV disable case
>       (Ville Syrjälä)
> v3: - Update icl_max_bw_qgv_point_mask to return max qgv point
>       mask (Vinod)
> v4: - Minor changes in icl_find_qgv_points (Vinod)
> 
> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bw.c | 80 +++++++++++++++----------
>  1 file changed, 50 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
> index 77886cc21211..c00094e5f11c 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.c
> +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> @@ -661,6 +661,22 @@ static unsigned int adl_psf_bw(struct drm_i915_private *dev_priv,
>  	return bi->psf_bw[psf_gv_point];
>  }
>  
> +static unsigned int icl_qgv_bw(struct drm_i915_private *i915,
> +			       int num_active_planes, int qgv_point)
> +{
> +	unsigned int idx;
> +
> +	if (DISPLAY_VER(i915) >= 12)
> +		idx = tgl_max_bw_index(i915, num_active_planes, qgv_point);
> +	else
> +		idx = icl_max_bw_index(i915, num_active_planes, qgv_point);
> +
> +	if (idx >= ARRAY_SIZE(i915->display.bw.max))
> +		return 0;
> +
> +	return i915->display.bw.max[idx].deratedbw[qgv_point];
> +}
> +
>  void intel_bw_init_hw(struct drm_i915_private *dev_priv)
>  {
>  	if (!HAS_DISPLAY(dev_priv))
> @@ -806,6 +822,35 @@ intel_atomic_get_bw_state(struct intel_atomic_state *state)
>  	return to_intel_bw_state(bw_state);
>  }
>  
> +static unsigned int icl_max_bw_qgv_point_mask(struct drm_i915_private *i915,
> +					      int num_active_planes)
> +{
> +	unsigned int num_qgv_points = i915->display.bw.max[0].num_qgv_points;
> +	unsigned int max_bw_point_mask = 0;
> +	unsigned int max_bw = 0;
> +	int i;
> +
> +	for (i = 0; i < num_qgv_points; i++) {
> +		unsigned int max_data_rate =
> +			icl_qgv_bw(i915, num_active_planes, i);
> +
> +		/*
> +		 * We need to know which qgv point gives us
> +		 * maximum bandwidth in order to disable SAGV
> +		 * if we find that we exceed SAGV block time
> +		 * with watermarks. By that moment we already
> +		 * have those, as it is calculated earlier in
> +		 * intel_atomic_check,
> +		 */
> +		if (max_data_rate > max_bw) {
> +			max_bw_point_mask = BIT(i);
> +			max_bw = max_data_rate;
> +		}
> +	}
> +
> +	return max_bw_point_mask;
> +}
> +

Wondering, why we just don't call it "max_bw_point", of course "mask"
could be applied to single point as well, however in most cases it still
kind of implies that there are few of those, however we always find
a single one here.

Stan

>  static int mtl_find_qgv_points(struct drm_i915_private *i915,
>  			       unsigned int data_rate,
>  			       unsigned int num_active_planes,
> @@ -883,8 +928,6 @@ static int icl_find_qgv_points(struct drm_i915_private *i915,
>  			       const struct intel_bw_state *old_bw_state,
>  			       struct intel_bw_state *new_bw_state)
>  {
> -	unsigned int max_bw_point = 0;
> -	unsigned int max_bw = 0;
>  	unsigned int num_psf_gv_points = i915->display.bw.max[0].num_psf_gv_points;
>  	unsigned int num_qgv_points = i915->display.bw.max[0].num_qgv_points;
>  	u16 psf_points = 0;
> @@ -897,31 +940,8 @@ static int icl_find_qgv_points(struct drm_i915_private *i915,
>  		return ret;
>  
>  	for (i = 0; i < num_qgv_points; i++) {
> -		unsigned int idx;
> -		unsigned int max_data_rate;
> -
> -		if (DISPLAY_VER(i915) >= 12)
> -			idx = tgl_max_bw_index(i915, num_active_planes, i);
> -		else
> -			idx = icl_max_bw_index(i915, num_active_planes, i);
> -
> -		if (idx >= ARRAY_SIZE(i915->display.bw.max))
> -			continue;
> -
> -		max_data_rate = i915->display.bw.max[idx].deratedbw[i];
> -
> -		/*
> -		 * We need to know which qgv point gives us
> -		 * maximum bandwidth in order to disable SAGV
> -		 * if we find that we exceed SAGV block time
> -		 * with watermarks. By that moment we already
> -		 * have those, as it is calculated earlier in
> -		 * intel_atomic_check,
> -		 */
> -		if (max_data_rate > max_bw) {
> -			max_bw_point = i;
> -			max_bw = max_data_rate;
> -		}
> +		unsigned int max_data_rate = icl_qgv_bw(i915,
> +							num_active_planes, i);
>  		if (max_data_rate >= data_rate)
>  			qgv_points |= BIT(i);
>  
> @@ -965,9 +985,9 @@ static int icl_find_qgv_points(struct drm_i915_private *i915,
>  	 * cause.
>  	 */
>  	if (!intel_can_enable_sagv(i915, new_bw_state)) {
> -		qgv_points = BIT(max_bw_point);
> -		drm_dbg_kms(&i915->drm, "No SAGV, using single QGV point %d\n",
> -			    max_bw_point);
> +		qgv_points = icl_max_bw_qgv_point_mask(i915, num_active_planes);
> +		drm_dbg_kms(&i915->drm, "No SAGV, using single QGV point mask 0x%x\n",
> +			    qgv_points);
>  	}
>  
>  	/*
> -- 
> 2.34.1
>