commit 117ed5c2d0f865894dd930d877f0ec28bc23d951
Author: Miroslav Lichvar <mlichvar@redhat.com>
Date:   Tue Jan 17 14:17:41 2017 +0100

    timemaster: check support for SW time stamping.
    
    When an interface doesn't support HW time stamping, before falling back
    to SW time stamping, check if it's actually supported and exit with an
    error message if not.
    
    Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>

diff --git a/timemaster.c b/timemaster.c
index 880b2ab..cda2d90 100644
--- a/timemaster.c
+++ b/timemaster.c
@@ -674,13 +674,15 @@ static int add_ptp_source(struct ptp_domain *source,
 {
 	struct config_file *config_file;
 	char **command, *uds_path, **interfaces, *message_tag;
-	int i, j, num_interfaces, *phc, *phcs, hw_ts;
+	int i, j, num_interfaces, *phc, *phcs, hw_ts, sw_ts;
 	struct sk_ts_info ts_info;
 
 	pr_debug("adding PTP domain %d", source->domain);
 
 	hw_ts = SOF_TIMESTAMPING_TX_HARDWARE | SOF_TIMESTAMPING_RX_HARDWARE |
 		SOF_TIMESTAMPING_RAW_HARDWARE;
+	sw_ts = SOF_TIMESTAMPING_TX_SOFTWARE | SOF_TIMESTAMPING_RX_SOFTWARE |
+		SOF_TIMESTAMPING_SOFTWARE;
 
 	for (num_interfaces = 0;
 	     source->interfaces[num_interfaces]; num_interfaces++)
@@ -702,9 +704,14 @@ static int add_ptp_source(struct ptp_domain *source,
 			return 1;
 		}
 
-		if (!ts_info.valid ||
-		    ((ts_info.so_timestamping & hw_ts) != hw_ts)) {
+		if (((ts_info.so_timestamping & hw_ts) != hw_ts)) {
 			pr_debug("interface %s: no PHC", source->interfaces[i]);
+			if ((ts_info.so_timestamping & sw_ts) != sw_ts) {
+				pr_err("time stamping not supported on %s",
+				       source->interfaces[i]);
+				free(phcs);
+				return 1;
+			}
 			continue;
 		}