linux-kernel - [PATCH 5.14 292/432] drm/msm/dp: return correct edid checksum after corrupted edid checksum read

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Message-Id: <20210916155820.722956261@linuxfoundation.org>
Date:   Thu, 16 Sep 2021 18:00:41 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kuogee Hsieh <khsieh@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Rob Clark <robdclark@...omium.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.14 292/432] drm/msm/dp: return correct edid checksum after corrupted edid checksum read

From: Kuogee Hsieh <khsieh@...eaurora.org>

[ 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@...eaurora.org>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
Link: https://lore.kernel.org/r/1628196295-7382-6-git-send-email-khsieh@codeaurora.org
Signed-off-by: Rob Clark <robdclark@...omium.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 440b32753430..2181b60e1d1d 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -271,7 +271,7 @@ 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");
@@ -303,7 +303,12 @@ 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