Commit 94b6ada4 authored Mar 06, 2020 by Lyude Paul

drm/dp_mst: Fix drm_dp_check_mstb_guid() return code



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: cb897542 ("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>

parent 4c0a9b62

drivers/gpu/drm/drm_dp_mst_topology.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -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);

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