From: jsg <jsg@openbsd.org>
Date: Fri, 16 Sep 2022 02:29:47 +0000 (+0000)
Subject: drm/i915: Implement WaEdpLinkRateDataReload
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=f7cabdec391f1d65c4d4b1c24c3a24ac573cee1f;p=openbsd

drm/i915: Implement WaEdpLinkRateDataReload

From Ville Syrjala
d2ca79dd0b5487991dac52c6b679915dbd70ee4c in linux 5.15.y/5.15.68
672d6ca758651f0ec12cd0d59787067a5bde1c96 in mainline linux
---

diff --git a/sys/dev/pci/drm/i915/display/intel_dp_link_training.c b/sys/dev/pci/drm/i915/display/intel_dp_link_training.c
index 508a514c5e3..d77d91c0a03 100644
--- a/sys/dev/pci/drm/i915/display/intel_dp_link_training.c
+++ b/sys/dev/pci/drm/i915/display/intel_dp_link_training.c
@@ -475,6 +475,28 @@ intel_dp_prepare_link_train(struct intel_dp *intel_dp,
 	intel_dp_compute_rate(intel_dp, crtc_state->port_clock,
 			      &link_bw, &rate_select);
 
+	/*
+	 * WaEdpLinkRateDataReload
+	 *
+	 * Parade PS8461E MUX (used on varius TGL+ laptops) needs
+	 * to snoop the link rates reported by the sink when we
+	 * use LINK_RATE_SET in order to operate in jitter cleaning
+	 * mode (as opposed to redriver mode). Unfortunately it
+	 * loses track of the snooped link rates when powered down,
+	 * so we need to make it re-snoop often. Without this high
+	 * link rates are not stable.
+	 */
+	if (!link_bw) {
+		struct intel_connector *connector = intel_dp->attached_connector;
+		__le16 sink_rates[DP_MAX_SUPPORTED_RATES];
+
+		drm_dbg_kms(&i915->drm, "[CONNECTOR:%d:%s] Reloading eDP link rates\n",
+			    connector->base.base.id, connector->base.name);
+
+		drm_dp_dpcd_read(&intel_dp->aux, DP_SUPPORTED_LINK_RATES,
+				 sink_rates, sizeof(sink_rates));
+	}
+
 	if (link_bw)
 		drm_dbg_kms(&i915->drm,
 			    "Using LINK_BW_SET value %02x\n", link_bw);