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* [PATCH 1/2] drm/i915/dp: Reject HBR3 when sink doesn't support TPS4
@ 2025-03-03 12:39 Ville Syrjala
  2025-03-03 12:39 ` [PATCH 2/2] drm/i915: Program CURSOR_PROGRAM and COEFF_POLARITY for icl+ combo PHYs Ville Syrjala
                   ` (8 more replies)
  0 siblings, 9 replies; 12+ messages in thread
From: Ville Syrjala @ 2025-03-03 12:39 UTC (permalink / raw)
  To: intel-gfx; +Cc: stable

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

According to the DP spec TPS4 is mandatory for HBR3. We have
however seen some broken eDP sinks that violate this and
declare support for HBR3 without TPS4 support.

At least in the case of the icl Dell XPS 13 7390 this results
in an unstable output.

Reject HBR3 when TPS4 supports is unavailable on the sink.

Cc: stable@vger.kernel.org
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/5969
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp.c | 36 ++++++++++++++++++++-----
 1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index 205ec315b413..61a58ff801a5 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -172,10 +172,22 @@ int intel_dp_link_symbol_clock(int rate)
 
 static int max_dprx_rate(struct intel_dp *intel_dp)
 {
+	int max_rate;
+
 	if (intel_dp_tunnel_bw_alloc_is_enabled(intel_dp))
-		return drm_dp_tunnel_max_dprx_rate(intel_dp->tunnel);
+		max_rate = drm_dp_tunnel_max_dprx_rate(intel_dp->tunnel);
+	else
+		max_rate = drm_dp_bw_code_to_link_rate(intel_dp->dpcd[DP_MAX_LINK_RATE]);
+
+	/*
+	 * Some broken eDP sinks illegally declare support for
+	 * HBR3 without TPS4, and are unable to produce a stable
+	 * output. Reject HBR3 when TPS4 is not available.
+	 */
+	if (!drm_dp_tps4_supported(intel_dp->dpcd))
+		max_rate = min(max_rate, 540000);
 
-	return drm_dp_bw_code_to_link_rate(intel_dp->dpcd[DP_MAX_LINK_RATE]);
+	return max_rate;
 }
 
 static int max_dprx_lane_count(struct intel_dp *intel_dp)
@@ -4180,10 +4192,7 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp)
 				 sink_rates, sizeof(sink_rates));
 
 		for (i = 0; i < ARRAY_SIZE(sink_rates); i++) {
-			int val = le16_to_cpu(sink_rates[i]);
-
-			if (val == 0)
-				break;
+			int rate;
 
 			/* Value read multiplied by 200kHz gives the per-lane
 			 * link rate in kHz. The source rates are, however,
@@ -4191,7 +4200,20 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp)
 			 * back to symbols is
 			 * (val * 200kHz)*(8/10 ch. encoding)*(1/8 bit to Byte)
 			 */
-			intel_dp->sink_rates[i] = (val * 200) / 10;
+			rate = le16_to_cpu(sink_rates[i]) * 200 / 10;
+
+			if (rate == 0)
+				break;
+
+			/*
+			 * Some broken eDP sinks illegally declare support for
+			 * HBR3 without TPS4, and are unable to produce a stable
+			 * output. Reject HBR3 when TPS4 is not available.
+			 */
+			if (rate >= 810000 && !drm_dp_tps4_supported(intel_dp->dpcd))
+				break;
+
+			intel_dp->sink_rates[i] = rate;
 		}
 		intel_dp->num_sink_rates = i;
 	}
-- 
2.45.3


^ permalink raw reply related	[flat|nested] 12+ messages in thread
end of thread, other threads:[~2025-03-27  7:36 UTC | newest]

Thread overview: 12+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2025-03-03 12:39 [PATCH 1/2] drm/i915/dp: Reject HBR3 when sink doesn't support TPS4 Ville Syrjala
2025-03-03 12:39 ` [PATCH 2/2] drm/i915: Program CURSOR_PROGRAM and COEFF_POLARITY for icl+ combo PHYs Ville Syrjala
2025-03-07  5:51   ` Borah, Chaitanya Kumar
2025-03-03 15:14 ` ✗ Fi.CI.CHECKPATCH: warning for series starting with [1/2] drm/i915/dp: Reject HBR3 when sink doesn't support TPS4 Patchwork
2025-03-03 15:32 ` ✓ i915.CI.BAT: success " Patchwork
2025-03-03 17:53 ` ✓ i915.CI.Full: " Patchwork
2025-03-04  9:05 ` [PATCH 1/2] " Jani Nikula
2025-03-06 21:07 ` [PATCH v2 " Ville Syrjala
2025-03-27  7:35   ` Jani Nikula
2025-03-06 21:56 ` ✗ Fi.CI.CHECKPATCH: warning for series starting with [v2,1/2] drm/i915/dp: Reject HBR3 when sink doesn't support TPS4 (rev2) Patchwork
2025-03-06 22:16 ` ✓ i915.CI.BAT: success " Patchwork
2025-03-06 23:53 ` ✗ i915.CI.Full: failure " Patchwork

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