[PATCH v2 7/7] x86/boot: Support nocfg parameter for earlyprintk

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

If by BIOS or by other means the serial port is configured
user might want to skip reconfiguration in the boot code.

Add support of 'nocfg' parameter to earlyprintk.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 arch/x86/boot/early_serial_console.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
index cfc9e55cd68a..5b4a81bf5d0e 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -80,9 +80,10 @@ static void early_serial_use_mmio_accessors(void)
 	serial_out = mem8_serial_out;
 }
 
-static void early_serial_init(unsigned long port, int baud)
+static void early_serial_init(unsigned long port, int baud, bool configure)
 {
-	early_serial_configure(port, baud);
+	if (configure)
+		early_serial_configure(port, baud);
 
 	early_serial_base = port;
 }
@@ -101,12 +102,22 @@ static unsigned long parse_serial_port(const char *arg, int off, int *pos)
 	return port;
 }
 
+static bool parse_serial_configure(const char *arg, int off, int *pos)
+{
+	if (strncmp(arg + off, "nocfg", 5))
+		return true;
+
+	*pos = off + 5;
+	return false;
+}
+
 static void parse_earlyprintk(void)
 {
 	int baud = DEFAULT_BAUD;
 	char arg[64];
 	int pos = 0;
 	unsigned long port = 0;
+	bool configure = true;
 
 	if (cmdline_find_option("earlyprintk", arg, sizeof(arg)) > 0) {
 		char *e;
@@ -146,6 +157,11 @@ static void parse_earlyprintk(void)
 			early_serial_use_io_accessors();
 		}
 
+		if (arg[pos] == ',')
+			pos++;
+
+		configure = parse_serial_configure(arg, pos, &pos);
+
 		if (arg[pos] == ',')
 			pos++;
 
@@ -155,7 +171,7 @@ static void parse_earlyprintk(void)
 	}
 
 	if (port)
-		early_serial_init(port, baud);
+		early_serial_init(port, baud, configure);
 }
 
 #define BASE_BAUD (1843200/16)
@@ -179,6 +195,7 @@ static void parse_console_uart8250(void)
 	char optstr[64], *options;
 	int baud = DEFAULT_BAUD;
 	unsigned long port = 0;
+	bool configure = true;
 
 	/*
 	 * console=uart8250,io,0x3f8,115200n8
@@ -204,7 +221,7 @@ static void parse_console_uart8250(void)
 		baud = probe_baud(port);
 
 	if (port)
-		early_serial_init(port, baud);
+		early_serial_init(port, baud, configure);
 }
 
 void console_init(void)
-- 
2.20.1