Re: [Intel-gfx] [PATCH v2] drm/i915: Update memory bandwidth formulae

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

On Tue, 28 Sep 2021, Radhakrishna Sripada <radhakrishna.sripada@intel.com> wrote:
> The formulae has been updated to include more variables. Make
> sure the code carries the same.
>
> Bspec: 64631
>
> v2: Make GEN11 follow the default route and fix calculation of
>     maxdebw(RK)
>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Suggested-by: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bw.c | 71 +++++++++++++++++++------
>  1 file changed, 55 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
> index 4b94256d7319..d24b2000bc3f 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.c
> +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> @@ -27,6 +27,9 @@ struct intel_qgv_info {
>  	u8 num_points;
>  	u8 num_psf_points;
>  	u8 t_bl;
> +	u8 max_numchannels;
> +	u8 channel_width;
> +	u8 deinterleave;
>  };
>  
>  static int dg1_mchbar_read_qgv_point_info(struct drm_i915_private *dev_priv,
> @@ -137,6 +140,7 @@ static int icl_get_qgv_points(struct drm_i915_private *dev_priv,
>  {
>  	const struct dram_info *dram_info = &dev_priv->dram_info;
>  	int i, ret;
> +	bool is_y_tile = true; /* assume y tile may be used */
>  
>  	qi->num_points = dram_info->num_qgv_points;
>  	qi->num_psf_points = dram_info->num_psf_gv_points;
> @@ -144,10 +148,31 @@ static int icl_get_qgv_points(struct drm_i915_private *dev_priv,
>  	if (DISPLAY_VER(dev_priv) == 12)
>  		switch (dram_info->type) {
>  		case INTEL_DRAM_DDR4:
> -			qi->t_bl = 4;
> +			qi->t_bl = is_y_tile ? 8 : 4;
> +			qi->max_numchannels = 2;
> +			qi->channel_width = 64;
> +			qi->deinterleave = is_y_tile ? 1 : 2;
>  			break;
>  		case INTEL_DRAM_DDR5:
> -			qi->t_bl = 8;
> +			qi->t_bl = is_y_tile ? 16 : 8;
> +			qi->max_numchannels = 4;
> +			qi->channel_width = 32;
> +			qi->deinterleave = is_y_tile ? 1 : 2;
> +			break;
> +		case INTEL_DRAM_LPDDR4:
> +			if (IS_ROCKETLAKE(dev_priv)) {
> +				qi->t_bl = 8;
> +				qi->max_numchannels = 4;
> +				qi->channel_width = 32;
> +				qi->deinterleave = 2;
> +				break;
> +			}
> +		fallthrough;

Just a drive-by comment, the fallthrough; line needs more indent.

BR,
Jani.

> +		case INTEL_DRAM_LPDDR5:
> +			qi->t_bl = 16;
> +			qi->max_numchannels = 8;
> +			qi->channel_width = 16;
> +			qi->deinterleave = is_y_tile ? 2 : 4;
>  			break;
>  		default:
>  			qi->t_bl = 16;
> @@ -263,12 +288,13 @@ static const struct intel_sa_info adlp_sa_info = {
>  static int icl_get_bw_info(struct drm_i915_private *dev_priv, const struct intel_sa_info *sa)
>  {
>  	struct intel_qgv_info qi = {};
> -	bool is_y_tile = true; /* assume y tile may be used */
> +	const struct dram_info *dram_info = &dev_priv->dram_info;
>  	int num_channels = max_t(u8, 1, dev_priv->dram_info.num_channels);
> -	int deinterleave;
>  	int ipqdepth, ipqdepthpch;
>  	int dclk_max;
> -	int maxdebw;
> +	int maxdebw, peakbw;
> +	int clperchgroup;
> +	int num_groups = ARRAY_SIZE(dev_priv->max_bw);
>  	int i, ret;
>  
>  	ret = icl_get_qgv_points(dev_priv, &qi);
> @@ -278,22 +304,38 @@ static int icl_get_bw_info(struct drm_i915_private *dev_priv, const struct intel
>  		return ret;
>  	}
>  
> -	deinterleave = DIV_ROUND_UP(num_channels, is_y_tile ? 4 : 2);
> -	dclk_max = icl_sagv_max_dclk(&qi);
> +	if (dram_info->type == INTEL_DRAM_LPDDR4 || dram_info->type == INTEL_DRAM_LPDDR5)
> +		num_channels *= 2;
> +
> +	if (num_channels < qi.max_numchannels && DISPLAY_VER(dev_priv) >= 12)
> +		qi.deinterleave = DIV_ROUND_UP(qi.deinterleave, 2);
> +
> +	num_channels = min_t(u8, num_channels, qi.max_numchannels);
> +	dclk_max = icl_calc_bw(icl_sagv_max_dclk(&qi), 16, 1);
>  
>  	ipqdepthpch = 16;
>  
> -	maxdebw = min(sa->deprogbwlimit * 1000,
> -		      icl_calc_bw(dclk_max, 16, 1) * 6 / 10); /* 60% */
> +	peakbw = num_channels * DIV_ROUND_UP(qi.deinterleave, 8) * dclk_max;
> +	maxdebw = min(sa->deprogbwlimit * 1000, peakbw * 6 / 10); /* 60% */
>  	ipqdepth = min(ipqdepthpch, sa->displayrtids / num_channels);
> +	/*
> +	 * clperchgroup = 4kpagespermempage * clperchperblock,
> +	 * clperchperblock = 8 /num_channels * interleave
> +	 */
> +	clperchgroup = 4 * DIV_ROUND_UP(8, num_channels) * qi.deinterleave;
>  
> -	for (i = 0; i < ARRAY_SIZE(dev_priv->max_bw); i++) {
> +	for (i = 0; i < num_groups; i++) {
>  		struct intel_bw_info *bi = &dev_priv->max_bw[i];
>  		int clpchgroup;
>  		int j;
>  
> -		clpchgroup = (sa->deburst * deinterleave / num_channels) << i;
> -		bi->num_planes = (ipqdepth - clpchgroup) / clpchgroup + 1;
> +		clpchgroup = (sa->deburst * qi.deinterleave / num_channels) << i;
> +
> +		if ((i < num_groups - 1 && clpchgroup < clperchgroup) ||
> +		    DISPLAY_VER(dev_priv) == 11)
> +			bi->num_planes = (ipqdepth - clpchgroup) / clpchgroup + 1;
> +		else
> +			bi->num_planes = 0;
>  
>  		bi->num_qgv_points = qi.num_points;
>  		bi->num_psf_gv_points = qi.num_psf_points;
> @@ -329,9 +371,6 @@ static int icl_get_bw_info(struct drm_i915_private *dev_priv, const struct intel
>  				    "BW%d / PSF GV %d: num_planes=%d bw=%u\n",
>  				    i, j, bi->num_planes, bi->psf_bw[j]);
>  		}
> -
> -		if (bi->num_planes == 1)
> -			break;
>  	}
>  
>  	/*
> @@ -339,7 +378,7 @@ static int icl_get_bw_info(struct drm_i915_private *dev_priv, const struct intel
>  	 * SAGV point, but we can't send PCode commands to restrict it
>  	 * as it will fail and pointless anyway.
>  	 */
> -	if (qi.num_points == 1)
> +	if (qi.num_points >= 1)
>  		dev_priv->sagv_status = I915_SAGV_NOT_CONTROLLED;
>  	else
>  		dev_priv->sagv_status = I915_SAGV_ENABLED;

-- 
Jani Nikula, Intel Open Source Graphics Center