don't switch from system clock to PHC with SW timestamping (#2179041)

Resolves: #2179041

linuxptp-vlanbond.patch

@@ -420,3 +420,32 @@ index ae9c4d3..96e097a 100644
  
  	/*
  	 * A port going down can affect the BMCA result.
+commit 8cf63218e4cc33d63bb783bf322d4a0d2f4be73e
+Author: Miroslav Lichvar <mlichvar@redhat.com>
+Date:   Wed Mar 15 11:24:16 2023 +0100
+
+    port: Don't switch to PHC with SW timestamping.
+    
+    When ptp4l was configured to use SW timestamping, but the interface
+    supported also HW timestamping, ptp4l detected a change of the PHC on
+    start, switched to it from the system clock, and tried to control the
+    PHC using SW timestamps.
+    
+    Don't switch the PHC if the current PHC index is -1, which is expected
+    with SW timestamping and in the free-running mode.
+    
+    Fixes: afeabf3c90ed ("ptp4l: add VLAN over bond support")
+    Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
+
+diff --git a/port.c b/port.c
+index 96e097a..32ee83b 100644
+--- a/port.c
++++ b/port.c
+@@ -2570,6 +2570,7 @@ static void port_change_phc(struct port *p)
+ 	/* Try to switch only if the interface is up, it has HW time stamping
+ 	   using a non-vclock PHC, and the PHC actually changed. */
+ 	if (!(p->link_status & LINK_UP) ||
++	    p->phc_index < 0 ||
+ 	    !interface_tsinfo_valid(p->iface) ||
+ 	    interface_get_vclock(p->iface) >= 0 ||
+ 	    interface_phc_index(p->iface) < 0 ||