We actually expect this to return a 0 on success, or negative error code
on failure. In order to do that, we check whether or not we managed to
write the whole GUID and then return 0 if so, otherwise return a
negative error code. Also, let's add an error message here so it's a
little more obvious when this fails in the middle of a link address
probe.
This should fix issues with certain MST hubs seemingly stopping for no
reason in the middle of the link address probe process.
Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
Cc: Benjamin Gaignard <benjamin.gaign...@st.com>
Cc: Sean Paul <s...@poorly.run>
Cc: Hans de Goede <hdego...@redhat.com>
Signed-off-by: Lyude Paul <ly...@redhat.com>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
b/drivers/gpu/drm/drm_dp_mst_topology.c
index e421c2d13267..b2ec6e8634ed 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2092,7 +2092,10 @@ static int drm_dp_check_mstb_guid(struct
drm_dp_mst_branch *mstb, u8 *guid)
}
}
- return ret;
+ if (ret < 16 && ret > 0)
+ return -EPROTO;
+
+ return ret == 16 ? 0 : ret;
}
static void build_mst_prop_path(const struct drm_dp_mst_branch *mstb,
@@ -2907,8 +2910,14 @@ static int drm_dp_send_link_address(struct
drm_dp_mst_topology_mgr *mgr,
drm_dp_dump_link_address(reply);
ret = drm_dp_check_mstb_guid(mstb, reply->guid);
- if (ret)
+ if (ret) {
+ char buf[64];
+
+ drm_dp_mst_rad_to_str(mstb->rad, mstb->lct, buf, sizeof(buf));
+ DRM_ERROR("GUID check on %s failed: %d\n",
+ buf, ret);
goto out;
+ }
for (i = 0; i < reply->nports; i++) {
port_mask |= BIT(reply->ports[i].port_number);
--
2.24.1
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