diff options
| author | Imre Deak <imre.deak@intel.com> | 2025-06-05 11:28:46 +0300 |
|---|---|---|
| committer | Joonas Lahtinen <joonas.lahtinen@linux.intel.com> | 2025-06-23 15:53:42 +0300 |
| commit | a3ef3c2da675a8a564c8bea1a511cdd0a2a9aa49 (patch) | |
| tree | 795285f59b21d63a5761ec8373960113181931e8 | |
| parent | 9205999e9f13a07cb29d5a8836c25afdca186007 (diff) | |
drm/dp: Change AUX DPCD probe address from DPCD_REV to LANE0_1_STATUS
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>
| -rw-r--r-- | drivers/gpu/drm/display/drm_dp_helper.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c index f2a6559a2710..dc622c78db9d 100644 --- a/drivers/gpu/drm/display/drm_dp_helper.c +++ b/drivers/gpu/drm/display/drm_dp_helper.c @@ -725,7 +725,7 @@ ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, * 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); if (ret < 0) return ret; } |