drm/amd/display: switch to guid_gen() to generate valid GUIDs

Instead of just smashing jiffies into a GUID, use guid_gen() to generate
RFC 4122 compliant GUIDs.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Acked-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240812122312.1567046-3-jani.nikula@intel.comSigned-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -2568,9 +2568,9 @@ static int dm_late_init(void *handle)
 
 static void resume_mst_branch_status(struct drm_dp_mst_topology_mgr *mgr)
 {
+	u8 buf[UUID_SIZE];
+	guid_t guid;
 	int ret;
-	u8 guid[16];
-	u64 tmp64;
 
 	mutex_lock(&mgr->lock);
 	if (!mgr->mst_primary)
@@ -2591,26 +2591,27 @@ static void resume_mst_branch_status(struct drm_dp_mst_topology_mgr *mgr)
 	}
 
 	/* Some hubs forget their guids after they resume */
-	ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, guid, 16);
-	if (ret != 16) {
+	ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, buf, sizeof(buf));
+	if (ret != sizeof(buf)) {
 		drm_dbg_kms(mgr->dev, "dpcd read failed - undocked during suspend?\n");
 		goto out_fail;
 	}
 
-	if (memchr_inv(guid, 0, 16) == NULL) {
-		tmp64 = get_jiffies_64();
-		memcpy(&guid[0], &tmp64, sizeof(u64));
-		memcpy(&guid[8], &tmp64, sizeof(u64));
+	import_guid(&guid, buf);
 
-		ret = drm_dp_dpcd_write(mgr->aux, DP_GUID, guid, 16);
+	if (guid_is_null(&guid)) {
+		guid_gen(&guid);
+		export_guid(buf, &guid);
 
-		if (ret != 16) {
+		ret = drm_dp_dpcd_write(mgr->aux, DP_GUID, buf, sizeof(buf));
+
+		if (ret != sizeof(buf)) {
 			drm_dbg_kms(mgr->dev, "check mstb guid failed - undocked during suspend?\n");
 			goto out_fail;
 		}
 	}
 
-	import_guid(&mgr->mst_primary->guid, guid);
+	guid_copy(&mgr->mst_primary->guid, &guid);
 
 out_fail:
 	mutex_unlock(&mgr->lock);