drm/i915: Update memory bandwidth parameters

Earlier while calculating derated bw we would use 90% of the calculated
bw. Starting ADL-P we use a non standard derating. Updating the formulae
to reflect the same.

Bspec: 64631

v2: Use the new derating value only for ADL-P(MattR)

Fixes: 4d32fe2f14 ("drm/i915/adl_p: Update memory bandwidth parameters")
Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210914220744.16042-1-radhakrishna.sripada@intel.com

drivers/gpu/drm/i915/display/intel_bw.c

@@ -222,31 +222,42 @@ static int icl_sagv_max_dclk(const struct intel_qgv_info *qi)
 
 struct intel_sa_info {
 	u16 displayrtids;
-	u8 deburst, deprogbwlimit;
+	u8 deburst, deprogbwlimit, derating;
 };
 
 static const struct intel_sa_info icl_sa_info = {
 	.deburst = 8,
 	.deprogbwlimit = 25, /* GB/s */
 	.displayrtids = 128,
+	.derating = 10,
 };
 
 static const struct intel_sa_info tgl_sa_info = {
 	.deburst = 16,
 	.deprogbwlimit = 34, /* GB/s */
 	.displayrtids = 256,
+	.derating = 10,
 };
 
 static const struct intel_sa_info rkl_sa_info = {
 	.deburst = 16,
 	.deprogbwlimit = 20, /* GB/s */
 	.displayrtids = 128,
+	.derating = 10,
 };
 
 static const struct intel_sa_info adls_sa_info = {
 	.deburst = 16,
 	.deprogbwlimit = 38, /* GB/s */
 	.displayrtids = 256,
+	.derating = 10,
+};
+
+static const struct intel_sa_info adlp_sa_info = {
+	.deburst = 16,
+	.deprogbwlimit = 38, /* GB/s */
+	.displayrtids = 256,
+	.derating = 20,
 };
 
 static int icl_get_bw_info(struct drm_i915_private *dev_priv, const struct intel_sa_info *sa)
@@ -302,7 +313,7 @@ static int icl_get_bw_info(struct drm_i915_private *dev_priv, const struct intel
 			bw = icl_calc_bw(sp->dclk, clpchgroup * 32 * num_channels, ct);
 
 			bi->deratedbw[j] = min(maxdebw,
-					       bw * 9 / 10); /* 90% */
+					       bw * (100 - sa->derating) / 100);
 
 			drm_dbg_kms(&dev_priv->drm,
 				    "BW%d / QGV %d: num_planes=%d deratedbw=%u\n",
@@ -400,7 +411,9 @@ void intel_bw_init_hw(struct drm_i915_private *dev_priv)
 
 	if (IS_DG2(dev_priv))
 		dg2_get_bw_info(dev_priv);
-	else if (IS_ALDERLAKE_S(dev_priv) || IS_ALDERLAKE_P(dev_priv))
+	else if (IS_ALDERLAKE_P(dev_priv))
+		icl_get_bw_info(dev_priv, &adlp_sa_info);
+	else if (IS_ALDERLAKE_S(dev_priv))
 		icl_get_bw_info(dev_priv, &adls_sa_info);
 	else if (IS_ROCKETLAKE(dev_priv))
 		icl_get_bw_info(dev_priv, &rkl_sa_info);