From df09321ebc6592443e5fb248766727e127b214f0 Mon Sep 17 00:00:00 2001
From: Lyude Paul <lyude@redhat.com>
Date: Fri, 6 Mar 2020 18:49:22 -0500
Subject: drm/dp_mst: Fix drm_dp_check_mstb_guid() return code
Git-commit: 94b6ada401cbcf2e81f34ac7c5c4ca82154fd22e
Patch-mainline: v5.7-rc1
References: jsc#SLE-12680, jsc#SLE-12880, jsc#SLE-12882, jsc#SLE-12883, jsc#SLE-13496, jsc#SLE-15322
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.gaignard@st.com>
Cc: Sean Paul <sean@poorly.run>
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200306234923.547873-3-lyude@redhat.com
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Patrik Jakobsson <pjakobsson@suse.de>
---
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 9f0bc61e6dc1..9e16ea500a04 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,
@@ -2903,8 +2906,14 @@ 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);
--
2.28.0