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@xxxxxxxxxx>
Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
Cc: Benjamin Gaignard <benjamin.gaignard@xxxxxx>
Cc: Sean Paul <sean@xxxxxxxxxx>
Acked-by: Alex Deucher <alexander.deucher@xxxxxxx>
Reviewed-by: Sean Paul <sean@xxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20200424190722.775284-1-lyude@xxxxxxxxxx
---
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 77f6d2cbefac..46920e9be9e6 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3438,8 +3438,12 @@ 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:
--
2.25.3
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