linux-kernel - [PATCH AUTOSEL 5.15 08/20] drm/msm/dp: skip validity check for DP CTS EDID checksum

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Message-ID: <20231107122940.3762228-8-sashal@kernel.org>
Date:   Tue,  7 Nov 2023 07:29:02 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jani Nikula <jani.nikula@...el.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Kuogee Hsieh <khsieh@...eaurora.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Sasha Levin <sashal@...nel.org>, airlied@...il.com,
        daniel@...ll.ch, quic_vpolimer@...cinc.com,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 5.15 08/20] drm/msm/dp: skip validity check for DP CTS EDID checksum

From: Jani Nikula <jani.nikula@...el.com>

[ Upstream commit a251c9d8e30833b260101edb9383b176ee2b7cb1 ]

The DP CTS test for EDID last block checksum expects the checksum for
the last block, invalid or not. Skip the validity check.

For the most part (*), the EDIDs returned by drm_get_edid() will be
valid anyway, and there's the CTS workaround to get the checksum for
completely invalid EDIDs. See commit 7948fe12d47a ("drm/msm/dp: return
correct edid checksum after corrupted edid checksum read").

This lets us remove one user of drm_edid_block_valid() with hopes the
function can be removed altogether in the future.

(*) drm_get_edid() ignores checksum errors on CTA extensions.

Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Kuogee Hsieh <khsieh@...eaurora.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>
Cc: Rob Clark <robdclark@...il.com>
Cc: Sean Paul <sean@...rly.run>
Cc: Stephen Boyd <swboyd@...omium.org>
Cc: linux-arm-msm@...r.kernel.org
Cc: freedreno@...ts.freedesktop.org
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/555361/
Link: https://lore.kernel.org/r/20230901142034.580802-1-jani.nikula@intel.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/msm/dp/dp_panel.c | 21 ++-------------------
 1 file changed, 2 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
index 62b742e701d2c..f9d31069f4848 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -263,26 +263,9 @@ int dp_panel_get_modes(struct dp_panel *dp_panel,
 
 static u8 dp_panel_get_edid_checksum(struct edid *edid)
 {
-	struct edid *last_block;
-	u8 *raw_edid;
-	bool is_edid_corrupt = false;
+	edid += edid->extensions;
 
-	if (!edid) {
-		DRM_ERROR("invalid edid input\n");
-		return 0;
-	}
-
-	raw_edid = (u8 *)edid;
-	raw_edid += (edid->extensions * EDID_LENGTH);
-	last_block = (struct edid *)raw_edid;
-
-	/* block type extension */
-	drm_edid_block_valid(raw_edid, 1, false, &is_edid_corrupt);
-	if (!is_edid_corrupt)
-		return last_block->checksum;
-
-	DRM_ERROR("Invalid block, no checksum\n");
-	return 0;
+	return edid->checksum;
 }
 
 void dp_panel_handle_sink_request(struct dp_panel *dp_panel)
-- 
2.42.0