Hi Greg and stable team,
please drop this patch from all stable trees, since it results in screen flicker for one user at least, see: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14558
The original issue the patch fixed needs a different solution, taking into account the panel in issues/14558 as well, I'll follow up with any such fix instead of this one later.
So far I got a notification that the patch got queued for the 6.1, 6.6, 6.12, 6.15 stable trees, it should be removed from all.
Sorry for the trouble this caused.
Thanks, Imre
On Thu, Jul 03, 2025 at 04:42:44PM +0200, Greg Kroah-Hartman wrote:
6.1-stable review patch. If anyone has any objections, please let me know.
From: Imre Deak imre.deak@intel.com
commit a3ef3c2da675a8a564c8bea1a511cdd0a2a9aa49 upstream.
Reading DPCD registers has side-effects in general. In particular accessing registers outside of the link training register range (0x102-0x106, 0x202-0x207, 0x200c-0x200f, 0x2216) is explicitly forbidden by the DP v2.1 Standard, see
3.6.5.1 DPTX AUX Transaction Handling Mandates 3.6.7.4 128b/132b DP Link Layer LTTPR Link Training Mandates
Based on my tests, accessing the DPCD_REV register during the link training of an UHBR TBT DP tunnel sink leads to link training failures.
Solve the above by using the DP_LANE0_1_STATUS (0x202) register for the DPCD register access quirk.
Cc: stable@vger.kernel.org Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Jani Nikula jani.nikula@linux.intel.com Acked-by: Jani Nikula jani.nikula@intel.com Signed-off-by: Imre Deak imre.deak@intel.com Link: https://lore.kernel.org/r/20250605082850.65136-2-imre.deak@intel.com (cherry picked from commit a40c5d727b8111b5db424a1e43e14a1dcce1e77f) Signed-off-by: Joonas Lahtinen joonas.lahtinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
drivers/gpu/drm/display/drm_dp_helper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -663,7 +663,7 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_a * monitor doesn't power down exactly after the throw away read. */ if (!aux->is_remote) {
ret = drm_dp_dpcd_probe(aux, DP_DPCD_REV);
ret = drm_dp_dpcd_probe(aux, DP_LANE0_1_STATUS);