From 78acdd356ec0952718912a85c36879d02bcdbfe1 Mon Sep 17 00:00:00 2001
From: Lyude Paul <lyude@redhat.com>
Date: Fri, 24 Apr 2020 15:07:22 -0400
Subject: drm/dp_mst: Fix drm_dp_send_dpcd_write() return code
Git-commit: dbc05ae3867628abce5619bfab868a43818bdb0d
Patch-mainline: v5.7-rc4
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
drm_dp_mst_wait_tx_reply() returns > 1 if time elapsed in
wait_event_timeout() before check_txmsg_state(mgr, txmsg) evaluated to
true. However, we make the mistake of returning this time from
drm_dp_send_dpcd_write() on success instead of returning the number of
bytes written - causing spontaneous failures during link probing:
[drm:drm_dp_send_link_address [drm_kms_helper]] *ERROR* GUID check on
10:01 failed: 3975
Yikes! So, fix this by returning the number of bytes written on success
instead.
Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Sean Paul <sean@poorly.run>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Sean Paul <sean@poorly.run>
Link: https://patchwork.freedesktop.org/patch/msgid/20200424190722.775284-1-lyude@redhat.com
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 283615e44838..9d89ebf3a749 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3442,8 +3442,12 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
drm_dp_queue_down_tx(mgr, txmsg);
ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
- if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
- ret = -EIO;
+ if (ret > 0) {
+ if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
+ ret = -EIO;
+ else
+ ret = size;
+ }
kfree(txmsg);
fail_put:
--
2.28.0