[PATCH] drm/amd/display: fix dp kvm can't light up

[Tianci Yin]

From: "Tianci.Yin" <tianci.yin at amd.com>

[why]
The DP KVM failed to light up, since the lttpr_mode is not reset to
default value when failed to read LTTPR capabilities, and the
variable max_link_rate retains a initial value zero, this cause variable
link_rate be assigned to an error value zero, consquently pixel_clock
get wrong value zero, and kvm can't light up.

[how]
Reset lttpr_mode to default value when failed to read LTTPR
capabilities, so that the link_rate fallbacks to the minimum rate that
supported by link encoder and sink.

Signed-off-by: Tianci.Yin <tianci.yin at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
index 5688b15ca9e6..f9ae06103241 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c
@@ -5101,6 +5101,7 @@ bool dp_retrieve_lttpr_cap(struct dc_link *link)
 				sizeof(lttpr_dpcd_data));
 		if (status != DC_OK) {
 			DC_LOG_DP2("%s: Read LTTPR caps data failed.\n", __func__);
+			link->lttpr_mode = LTTPR_MODE_NON_LTTPR;
 			return false;
 		}
 
-- 
2.25.1