[PATCH 15/20] drm/amd/display: Correct DPCD revision for eDP v1.4

[Stylon Wang]

From: Zhan Liu <zhan.liu at amd.com>

[Why]
eDP version and DPCD revision are different. Per VESA
spec, "The DPCD revision for eDP v1.4 is 13h".

SUPPORTED_LINK_RATES is valid since eDP v1.4 (DPCD_REV_13).

[How]
Correct DPCD_REV for eDP v1.4.

Signed-off-by: Zhan Liu <zhan.liu at amd.com>
Reviewed-by: Nikola Cornij <Nikola.Cornij at amd.com>
Acked-by: Stylon Wang <stylon.wang at amd.com>
---
 drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

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 e860d7cd4fc6..9e08410bfdfd 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
@@ -2595,7 +2595,11 @@ bool decide_edp_link_settings(struct dc_link *link, struct dc_link_settings *lin
 	struct dc_link_settings current_link_setting;
 	uint32_t link_bw;
 
-	if (link->dpcd_caps.dpcd_rev.raw < DPCD_REV_14 ||
+	/*
+	 * edp_supported_link_rates_count is only valid for eDP v1.4 or higher.
+	 * Per VESA eDP spec, "The DPCD revision for eDP v1.4 is 13h"
+	 */
+	if (link->dpcd_caps.dpcd_rev.raw < DPCD_REV_13 ||
 			link->dpcd_caps.edp_supported_link_rates_count == 0) {
 		*link_setting = link->verified_link_cap;
 		return true;
@@ -4018,7 +4022,11 @@ void detect_edp_sink_caps(struct dc_link *link)
 	link->dpcd_caps.edp_supported_link_rates_count = 0;
 	memset(supported_link_rates, 0, sizeof(supported_link_rates));
 
-	if (link->dpcd_caps.dpcd_rev.raw >= DPCD_REV_14 &&
+	/*
+	 * edp_supported_link_rates_count is only valid for eDP v1.4 or higher.
+	 * Per VESA eDP spec, "The DPCD revision for eDP v1.4 is 13h"
+	 */
+	if (link->dpcd_caps.dpcd_rev.raw >= DPCD_REV_13 &&
 			(link->dc->debug.optimize_edp_link_rate ||
 			link->reported_link_cap.link_rate == LINK_RATE_UNKNOWN)) {
 		// Read DPCD 00010h - 0001Fh 16 bytes at one shot
-- 
2.25.1