linux-kernel - [PATCH] drm/dp_mst: Don't drop NAKs for down responses

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Date:   Fri,  3 Apr 2020 16:03:25 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Wayne Lin <Wayne.Lin@....com>, Wayne Lin <waynelin@....com>,
        Sean Paul <seanpaul@...omium.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/dp_mst: Don't drop NAKs for down responses

It looks like that when we introduced the ability to handle multiple
down requests at once, we accidentally started dropping NAK replies -
causing sideband messages which got NAK'd to seemingly timeout and cause
all sorts of weirdness.

So, fix this by making sure we don't return from
drm_dp_mst_handle_down_rep() early, but instead treat NAKs like any
other message.

Signed-off-by: Lyude Paul <lyude@...hat.com>
Fixes: fbc821c4a506 ("drm/mst: Support simultaneous down replies")
Cc: Wayne Lin <Wayne.Lin@....com>
Cc: Wayne Lin <waynelin@....com>
Cc: Sean Paul <seanpaul@...omium.org>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 10d0315af513..5449ada3e019 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3813,7 +3813,6 @@ static int drm_dp_mst_handle_down_rep(struct drm_dp_mst_topology_mgr *mgr)
 			      txmsg->reply.u.nak.reason,
 			      drm_dp_mst_nak_reason_str(txmsg->reply.u.nak.reason),
 			      txmsg->reply.u.nak.nak_data);
-		goto out_clear_reply;
 	}
 
 	memset(msg, 0, sizeof(struct drm_dp_sideband_msg_rx));
-- 
2.25.1