linux-kernel - [PATCH AUTOSEL 5.1 028/186] drm/nouveau/disp/dp: respect sink limits when selecting failsafe link configuration

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Date:   Sat,  1 Jun 2019 09:14:04 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ben Skeggs <bskeggs@...hat.com>, Sasha Levin <sashal@...nel.org>,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.1 028/186] drm/nouveau/disp/dp: respect sink limits when selecting failsafe link configuration

From: Ben Skeggs <bskeggs@...hat.com>

[ Upstream commit 13d03e9daf70dab032c03dc172e75bb98ad899c4 ]

Where possible, we want the failsafe link configuration (one which won't
hang the OR during modeset because of not enough bandwidth for the mode)
to also be supported by the sink.

This prevents "link rate unsupported by sink" messages when link training
fails.

Signed-off-by: Ben Skeggs <bskeggs@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c b/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c
index 5f301e632599b..818d21bd28d31 100644
--- a/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c
+++ b/drivers/gpu/drm/nouveau/nvkm/engine/disp/dp.c
@@ -365,8 +365,15 @@ nvkm_dp_train(struct nvkm_dp *dp, u32 dataKBps)
 	 * and it's better to have a failed modeset than that.
 	 */
 	for (cfg = nvkm_dp_rates; cfg->rate; cfg++) {
-		if (cfg->nr <= outp_nr && cfg->nr <= outp_bw)
-			failsafe = cfg;
+		if (cfg->nr <= outp_nr && cfg->nr <= outp_bw) {
+			/* Try to respect sink limits too when selecting
+			 * lowest link configuration.
+			 */
+			if (!failsafe ||
+			    (cfg->nr <= sink_nr && cfg->bw <= sink_bw))
+				failsafe = cfg;
+		}
+
 		if (failsafe && cfg[1].rate < dataKBps)
 			break;
 	}
-- 
2.20.1