[PATCH 5.10 209/306] drm/msm/dp: return correct edid checksum after corrupted edid checksum read

[Greg Kroah-Hartman]

From: Kuogee Hsieh <khsieh@xxxxxxxxxxxxxx>

[ Upstream commit 7948fe12d47a946fb8025a0534c900e3dd4b5839 ]

Response with correct edid checksum saved at connector after corrupted edid
checksum read. This fixes Link Layer CTS cases 4.2.2.3, 4.2.2.6.

Signed-off-by: Kuogee Hsieh <khsieh@xxxxxxxxxxxxxx>
Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/1628196295-7382-6-git-send-email-khsieh@xxxxxxxxxxxxxx
Signed-off-by: Rob Clark <robdclark@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/gpu/drm/msm/dp/dp_panel.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
index 18cec4fc5e0b..2768d1d306f0 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -261,7 +261,7 @@ static u8 dp_panel_get_edid_checksum(struct edid *edid)
 {
 	struct edid *last_block;
 	u8 *raw_edid;
-	bool is_edid_corrupt;
+	bool is_edid_corrupt = false;
 
 	if (!edid) {
 		DRM_ERROR("invalid edid input\n");
@@ -293,7 +293,12 @@ void dp_panel_handle_sink_request(struct dp_panel *dp_panel)
 	panel = container_of(dp_panel, struct dp_panel_private, dp_panel);
 
 	if (panel->link->sink_request & DP_TEST_LINK_EDID_READ) {
-		u8 checksum = dp_panel_get_edid_checksum(dp_panel->edid);
+		u8 checksum;
+
+		if (dp_panel->edid)
+			checksum = dp_panel_get_edid_checksum(dp_panel->edid);
+		else
+			checksum = dp_panel->connector->real_edid_checksum;
 
 		dp_link_send_edid_checksum(panel->link, checksum);
 		dp_link_send_test_response(panel->link);
-- 
2.30.2