drm/nouveau/disp/dp: respect sink limits when selecting failsafe link configuration

[ Upstream commit 13d03e9d ]

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@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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;
 	}