linux-kernel - [PATCH v1 6/6] x86/boot: Support nocfg parameter for earlyprintk

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Date:   Sun, 14 Jan 2018 16:32:54 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v1 6/6] x86/boot: Support nocfg parameter for earlyprintk

If by BIOS or by other means 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@...ux.intel.com>
---
 arch/x86/boot/early_serial_console.c | 31 +++++++++++++++++++++----------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
index ef10926ab9e5..f4759f485d8e 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -67,7 +67,7 @@ static void early_serial_configure(unsigned long port, int baud)
 	serial_out(port, LCR, c & ~DLAB);
 }
 
-static void early_serial_init(unsigned long port, int baud)
+static void early_serial_init(unsigned long port, int baud, bool configure)
 {
 	/* Assign serial I/O accessors */
 	if (port > IO_SPACE_LIMIT) {
@@ -82,7 +82,8 @@ static void early_serial_init(unsigned long port, int baud)
 		return;
 	}
 
-	early_serial_configure(port, baud);
+	if (configure)
+		early_serial_configure(port, baud);
 
 	early_serial_base = port;
 }
@@ -93,6 +94,7 @@ static void parse_earlyprintk(void)
 	char arg[64];
 	int pos = 0;
 	unsigned long port = 0;
+	bool configure = true;
 
 	if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
 		char *e;
@@ -133,12 +135,16 @@ static void parse_earlyprintk(void)
 		if (arg[pos] == ',')
 			pos++;
 
-		baud = simple_strtoull(arg + pos, &e, 0);
-		if (baud == 0 || arg + pos == e)
-			baud = DEFAULT_BAUD;
+		if (strncmp(arg + pos, "nocfg", 5)) {
+			baud = simple_strtoull(arg + pos, &e, 0);
+			if (baud == 0 || arg + pos == e)
+				baud = DEFAULT_BAUD;
+		} else {
+			configure = false;
+		}
 	}
 
-	early_serial_init(port, baud);
+	early_serial_init(port, baud, configure);
 }
 
 #define BASE_BAUD (1843200/16)
@@ -162,6 +168,7 @@ 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
@@ -179,12 +186,16 @@ static void parse_console_uart8250(void)
 	else
 		return;
 
-	if (options && (options[0] == ','))
-		baud = simple_strtoull(options + 1, &options, 0);
-	else
+	if (options[0] == ',') {
+		if (strncmp(options + 1, "nocfg", 5))
+			baud = simple_strtoull(options + 1, &options, 0);
+		else
+			configure = false;
+	} else {
 		baud = probe_baud(port);
+	}
 
-	early_serial_init(port, baud);
+	early_serial_init(port, baud, configure);
 }
 
 void console_init(void)
-- 
2.15.1