[PATCH 2/2][SRU][U] drm/dp/mst: Read the extended DPCD capabilities during system resume

Koba Ko koba.ko at canonical.com
Tue Jun 21 05:34:01 UTC 2022

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

BugLink: https://bugs.launchpad.net/bugs/1979267

The WD22TB4 Thunderbolt dock at least will revert its DP_MAX_LINK_RATE
from HBR3 to HBR2 after system suspend/resume if the DP_DP13_DPCD_REV
registers are not read subsequently also as required.

Fix this by reading DP_DP13_DPCD_REV registers as well, matching what is
done during connector detection. While at it also fix up the same call
in drm_dp_mst_dump_topology().

Cc: Lyude Paul <lyude at redhat.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5292
Signed-off-by: Imre Deak <imre.deak at intel.com>
Reviewed-by: Jani Nikula <jani.nikula at intel.com>
Reviewed-by: Lyude Paul <lyude at redhat.com>
Ref: https://patchwork.freedesktop.org/patch/489424/?series=105101&rev=1
Signed-off-by: Koba Ko <koba.ko at canonical.com>
 drivers/gpu/drm/display/drm_dp_mst_topology.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
index 67b3b9697da7f..18f2b6075b780 100644
--- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
@@ -3860,9 +3860,7 @@ int drm_dp_mst_topology_mgr_resume(struct drm_dp_mst_topology_mgr *mgr,
 	if (!mgr->mst_primary)
 		goto out_fail;
-	ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd,
-	if (ret != DP_RECEIVER_CAP_SIZE) {
+	if (drm_dp_read_dpcd_caps(mgr->aux, mgr->dpcd) < 0) {
 		drm_dbg_kms(mgr->dev, "dpcd read failed - undocked during suspend?\n");
 		goto out_fail;
@@ -4911,8 +4909,7 @@ void drm_dp_mst_dump_topology(struct seq_file *m,
 		int ret;
-		ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, buf, DP_RECEIVER_CAP_SIZE);
-		if (ret) {
+		if (drm_dp_read_dpcd_caps(mgr->aux, buf) < 0) {
 			seq_printf(m, "dpcd read failed\n");
 			goto out;

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