check-sof-logger: nudge the DMA trace when it's empty

See bug thesofproject/sof#4333

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

test-case/check-sof-logger.sh

@@ -106,6 +106,15 @@ print_logs_exit()
     # goes wrong and we don't make it until the end.
     test -z "$errmsg" || dloge "$errmsg"
 
+    # If the DMA trace is empty (ignoring the first header line) then
+    # try to nudge it a bit. See bug
+    # https://github.com/thesofproject/sof/issues/4333
+    tail -n +2  "${LOG_ROOT}"/logger.data.txt | grep -q . || (
+        dloge "Empty or stuck DMA trace? Let's try to nudge it:"
+        set -x
+        timeout -k 5  2  sudo "$loggerBin" -l "${ldcFile}" -F info=pga -t || true
+    )
+
     local bname
     for ftype in data etrace error etrace_stderr; do
         printf '\n\n'