[PATCH 3/6] drm/msm/dp: Limit voltage swing level to 2 for RA620 bridge

[Graham O'Connor]

The RA620 DP-to-HDMI bridge used on the Radxa Dragon Q6A does not
acknowledge DP link training at voltage swing level 3. The bridge
requests maximum voltage swing but never completes link training
when the driver attempts level 3, causing HDMI output to fail.

Cap DP_TRAIN_LEVEL_MAX at 2 to match the behaviour of the vendor
kernel, where link training completes successfully at level 2.
This allows the RA620 bridge to establish a stable HDMI connection.

Tested on Radxa Dragon Q6A (QCS6490) with RA620 DP-to-HDMI bridge

Signed-off-by: Graham O'Connor <graham.oconnor@xxxxxxxxx>
---
 drivers/gpu/drm/msm/dp/dp_link.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_link.h b/drivers/gpu/drm/msm/dp/dp_link.h
index 76125e9c0..ff0d8e99d 100644
--- a/drivers/gpu/drm/msm/dp/dp_link.h
+++ b/drivers/gpu/drm/msm/dp/dp_link.h
@@ -24,7 +24,7 @@ struct msm_dp_link_info {
 	unsigned long capabilities;
 };
 
-#define DP_TRAIN_LEVEL_MAX	3
+#define DP_TRAIN_LEVEL_MAX	2
 
 struct msm_dp_link_test_video {
 	u32 test_video_pattern;
-- 
2.53.0