x86, setup: Fix earlyprintk=serial,0x3f8,115200

earlyprintk can take and I/O port, so we need to handle this case in
the setup code too, otherwise 0x3f8 will be treated as a baud rate.

Signed-off-by: Yinghai Lu <[e-mail]>
LKML-Reference: <[e-mail]>
Signed-off-by: H. Peter Anvin <[e-mail]>

arch/x86/boot/early_serial_console.c

···
 		if (arg[pos] == ',')
 			pos++;
 
-		if (!strncmp(arg + pos, "ttyS", 4)) {
+		/*
+		 * make sure we have
+		 *	"serial,0x3f8,115200"
+		 *	"serial,ttyS0,115200"
+		 *	"ttyS0,115200"
+		 */
+		if (pos == 7 && !strncmp(arg + pos, "0x", 2)) {
+			port = simple_strtoull(arg + pos, &e, 16);
+			if (port == 0 || arg + pos == e)
+				port = DEFAULT_SERIAL_PORT;
+			else
+				pos = e - arg;
+		} else if (!strncmp(arg + pos, "ttyS", 4)) {
 			static const int bases[] = { 0x3f8, 0x2f8 };
 			int idx = 0;