linux-kernel - [PATCH 4/4] drm/dp_mst: Print errors on ACT timeouts

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Date:   Fri,  3 Apr 2020 16:07:56 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Sean Paul <sean@...rly.run>,
        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 4/4] drm/dp_mst: Print errors on ACT timeouts

Although it's not unexpected for drm_dp_check_act_status() to fail due
to DPCD read failures (as the hub may have just been unplugged
suddenly), timeouts are a bit more worrying as they either mean we need
a longer timeout value, or we aren't setting up payload allocations
properly. So, let's start printing errors on timeouts.

Signed-off-by: Lyude Paul <lyude@...hat.com>
Cc: Sean Paul <sean@...rly.run>
---
 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 f313407374ed..3d0d373f6f91 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -4494,6 +4494,10 @@ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr)
 					DP_PAYLOAD_TABLE_UPDATE_STATUS,
 					&status);
 		if (ret < 0) {
+			/*
+			 * Failure here isn't unexpected - the hub may have
+			 * just been unplugged
+			 */
 			DRM_DEBUG_KMS("failed to read payload table status %d\n",
 				      ret);
 			return ret;
@@ -4505,8 +4509,8 @@ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr)
 	} while (jiffies < timeout);
 
 	if (!(status & DP_PAYLOAD_ACT_HANDLED)) {
-		DRM_DEBUG_KMS("failed to get ACT bit %d after %dms\n",
-			      status, timeout_ms);
+		DRM_ERROR("Failed to get ACT after %dms, last status: %02x\n",
+			  timeout_ms, status);
 		return -EINVAL;
 	}
 	return 0;
-- 
2.25.1