linux-kernel - [PATCH 5.19 0088/1157] drm/dp/mst: Read the extended DPCD capabilities during system resume

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Message-Id: <20220815180443.089201685@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 19:50:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lyude Paul <lyude@...hat.com>,
        Imre Deak <imre.deak@...el.com>,
        Jani Nikula <jani.nikula@...el.com>
Subject: [PATCH 5.19 0088/1157] drm/dp/mst: Read the extended DPCD capabilities during system resume

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

commit 7a710a8bc909313951eb9252d8419924c771d7c2 upstream.

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@...hat.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5292
Signed-off-by: Imre Deak <imre.deak@...el.com>
Reviewed-by: Jani Nikula <jani.nikula@...el.com>
Cc: <stable@...r.kernel.org> # v5.14+
Reviewed-by: Lyude Paul <lyude@...hat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220614094537.885472-1-imre.deak@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpu/drm/display/drm_dp_mst_topology.c |    7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

--- 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(struc
 	if (!mgr->mst_primary)
 		goto out_fail;
 
-	ret = drm_dp_dpcd_read(mgr->aux, DP_DPCD_REV, mgr->dpcd,
-			       DP_RECEIVER_CAP_SIZE);
-	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
 		u8 buf[DP_PAYLOAD_TABLE_SIZE];
 		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;
 		}