[PATCH 5.4 23/23] Revert "drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS"

[PATCH 5.4 23/23] Revert "drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS"

[Greg Kroah-Hartman]

5.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Imre Deak <imre.deak@intel.com>

This reverts commit 2402adce8da4e7396b63b5ffa71e1fa16e5fe5c4 which is
commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f upstream.

The upstream commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f ("drm/dp:
Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS") the
reverted commit backported causes a regression, on one eDP panel at
least resulting in display flickering, described in detail at the Link:
below. The issue fixed by the upstream commit will need a different
solution, revert the backport for now.

Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Cc: Sasha Levin <sashal@kernel.org>
Link: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14558
Signed-off-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/drm_dp_helper.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -280,7 +280,7 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_a
 	 * We just have to do it before any DPCD access and hope that the
 	 * monitor doesn't power down exactly after the throw away read.
 	 */
-	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_LANE0_1_STATUS, buffer,
+	ret = drm_dp_dpcd_access(aux, DP_AUX_NATIVE_READ, DP_DPCD_REV, buffer,
 				 1);
 	if (ret != 1)
 		goto out;