drm/i915/dp: Optimize the FRL configuration for HDMI2.1 PCON

Currently the HDMI2.1 PCON's frl link config DPCD registers are
reset and configured even if they are already configured.
Also the HDMI Link Mode does not settle to FRL MODE immediately after
HDMI Link Status is active.

This patch:
-Checks if the PCON is already configured for FRL.
-Include HDMI Link Mode in wait for loop along with HDMI Link status DPCD.

v2: Rebase
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211110072947.171659-2-ankit.k.nautiyal@intel.com

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

@@ -2198,6 +2198,18 @@ static int intel_dp_hdmi_sink_max_frl(struct intel_dp *intel_dp)
 	return max_frl_rate;
 }
 
+static bool
+intel_dp_pcon_is_frl_trained(struct intel_dp *intel_dp,
+			     u8 max_frl_bw_mask, u8 *frl_trained_mask)
+{
+	if (drm_dp_pcon_hdmi_link_active(&intel_dp->aux) &&
+	    drm_dp_pcon_hdmi_link_mode(&intel_dp->aux, frl_trained_mask) == DP_PCON_HDMI_MODE_FRL &&
+	    *frl_trained_mask >= max_frl_bw_mask)
+		return true;
+
+	return false;
+}
+
 static int intel_dp_pcon_start_frl_training(struct intel_dp *intel_dp)
 {
 #define TIMEOUT_FRL_READY_MS 500
@@ -2208,10 +2220,6 @@ static int intel_dp_pcon_start_frl_training(struct intel_dp *intel_dp)
 	u8 max_frl_bw_mask = 0, frl_trained_mask;
 	bool is_active;
 
-	ret = drm_dp_pcon_reset_frl_config(&intel_dp->aux);
-	if (ret < 0)
-		return ret;
-
 	max_pcon_frl_bw = intel_dp->dfp.pcon_max_frl_bw;
 	drm_dbg(&i915->drm, "PCON max rate = %d Gbps\n", max_pcon_frl_bw);
 
@@ -2223,6 +2231,12 @@ static int intel_dp_pcon_start_frl_training(struct intel_dp *intel_dp)
 	if (max_frl_bw <= 0)
 		return -EINVAL;
 
+	max_frl_bw_mask = intel_dp_pcon_set_frl_mask(max_frl_bw);
+	drm_dbg(&i915->drm, "MAX_FRL_BW_MASK = %u\n", max_frl_bw_mask);
+
+	if (intel_dp_pcon_is_frl_trained(intel_dp, max_frl_bw_mask, &frl_trained_mask))
+		goto frl_trained;
+
 	ret = drm_dp_pcon_frl_prepare(&intel_dp->aux, false);
 	if (ret < 0)
 		return ret;
@@ -2232,7 +2246,6 @@ static int intel_dp_pcon_start_frl_training(struct intel_dp *intel_dp)
 	if (!is_active)
 		return -ETIMEDOUT;
 
-	max_frl_bw_mask = intel_dp_pcon_set_frl_mask(max_frl_bw);
 	ret = drm_dp_pcon_frl_configure_1(&intel_dp->aux, max_frl_bw,
 					  DP_PCON_ENABLE_SEQUENTIAL_LINK);
 	if (ret < 0)
@@ -2248,19 +2261,15 @@ static int intel_dp_pcon_start_frl_training(struct intel_dp *intel_dp)
 	 * Wait for FRL to be completed
 	 * Check if the HDMI Link is up and active.
 	 */
-	wait_for(is_active = drm_dp_pcon_hdmi_link_active(&intel_dp->aux) == true, TIMEOUT_HDMI_LINK_ACTIVE_MS);
+	wait_for(is_active =
+		 intel_dp_pcon_is_frl_trained(intel_dp, max_frl_bw_mask, &frl_trained_mask),
+		 TIMEOUT_HDMI_LINK_ACTIVE_MS);
 
 	if (!is_active)
 		return -ETIMEDOUT;
 
-	/* Verify HDMI Link configuration shows FRL Mode */
-	if (drm_dp_pcon_hdmi_link_mode(&intel_dp->aux, &frl_trained_mask) !=
-	    DP_PCON_HDMI_MODE_FRL) {
-		drm_dbg(&i915->drm, "HDMI couldn't be trained in FRL Mode\n");
-		return -EINVAL;
-	}
-	drm_dbg(&i915->drm, "MAX_FRL_MASK = %u, FRL_TRAINED_MASK = %u\n", max_frl_bw_mask, frl_trained_mask);
-
+frl_trained:
+	drm_dbg(&i915->drm, "FRL_TRAINED_MASK = %u\n", frl_trained_mask);
 	intel_dp->frl.trained_rate_gbps = intel_dp_pcon_get_frl_mask(frl_trained_mask);
 	intel_dp->frl.is_trained = true;
 	drm_dbg(&i915->drm, "FRL trained with : %d Gbps\n", intel_dp->frl.trained_rate_gbps);