powerpc/xmon: Dump ftrace buffers for the current CPU only

Current xmon 'dt' command dumps the tracing buffer for all the CPUs,
which makes it very hard to read due to the fact that most of
powerpc machines currently have many CPUs. Other than that, the CPU
lines are interleaved in the ftrace log.

This new option just dumps the ftrace buffer for the current CPU.
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/xmon/xmon.c

@@ -234,6 +234,7 @@ Commands:\n\
   "\
   dr	dump stream of raw bytes\n\
   dt	dump the tracing buffers (uses printk)\n\
+  dtc	dump the tracing buffers for current CPU (uses printk)\n\
 "
 #ifdef CONFIG_PPC_POWERNV
 "  dx#   dump xive on CPU #\n\
@@ -2231,6 +2232,19 @@ static void xmon_rawdump (unsigned long adrs, long ndump)
 	printf("\n");
 }
 
+static void dump_tracing(void)
+{
+	int c;
+
+	c = inchar();
+	if (c == 'c')
+		ftrace_dump(DUMP_ORIG);
+	else
+		ftrace_dump(DUMP_ALL);
+
+	tracing_on();
+}
+
 #ifdef CONFIG_PPC64
 static void dump_one_paca(int cpu)
 {
@@ -2507,6 +2521,11 @@ dump(void)
 	}
 #endif
 
+	if (c == 't') {
+		dump_tracing();
+		return;
+	}
+
 	if (c == '\n')
 		termch = c;
 
@@ -2525,9 +2544,6 @@ dump(void)
 		dump_log_buf();
 	} else if (c == 'o') {
 		dump_opal_msglog();
-	} else if (c == 't') {
-		ftrace_dump(DUMP_ALL);
-		tracing_on();
 	} else if (c == 'r') {
 		scanhex(&ndump);
 		if (ndump == 0)