x86, setup: Make the setup code also accept console=uart8250

Make the boot code also accept the console=uart8250,io,0x2f8,115200n
form of early console.

Also add back simple_guess_base(), otherwise those simple_strtoull(,,0)
are not going to work.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <4C3CCE05.4090505@kernel.org>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 58 insertions, 1 deletions

diff --git a/arch/x86/boot/tty.c b/arch/x86/boot/tty.c
index f3ceee20ff12..f6d52e65f97a 100644
--- a/arch/x86/boot/tty.c
+++ b/arch/x86/boot/tty.c
@@ -170,7 +170,7 @@ static void early_serial_init(int baud)
         outb(c & ~DLAB, early_serial_base + LCR);
 }
 
-void console_init(void)
+static int parse_earlyprintk(void)
 {
         int baud = DEFAULT_BAUD;
         char arg[32];
@@ -208,6 +208,63 @@ void console_init(void)
                         baud = DEFAULT_BAUD;
         }
 
+        return baud;
+}
+
+#define BASE_BAUD (1843200/16)
+static unsigned int probe_baud(int port)
+{
+        unsigned char lcr, dll, dlh;
+        unsigned int quot;
+
+        lcr = inb(port + LCR);
+        outb(lcr | DLAB, port + LCR);
+        dll = inb(port + DLL);
+        dlh = inb(port + DLH);
+        outb(lcr, port + LCR);
+        quot = (dlh << 8) | dll;
+
+        return BASE_BAUD / quot;
+}
+
+static int parse_console_uart8250(void)
+{
+        char optstr[64], *options;
+        int baud = DEFAULT_BAUD;
+
+        /*
+         * console=uart8250,io,0x3f8,115200n8
+         * need to make sure it is last one console !
+         */
+        if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
+                return baud;
+
+        options = optstr;
+
+        if (!strncmp(options, "uart8250,io,", 12))
+                early_serial_base = simple_strtoull(options + 12, &options, 0);
+        else if (!strncmp(options, "uart,io,", 8))
+                early_serial_base = simple_strtoull(options + 8, &options, 0);
+        else
+                return baud;
+
+        if (options && (options[0] == ','))
+                baud = simple_strtoull(options + 1, &options, 0);
+        else
+                baud = probe_baud(early_serial_base);
+
+        return baud;
+}
+
+void console_init(void)
+{
+        int baud;
+
+        baud = parse_earlyprintk();
+
+        if (!early_serial_base)
+                baud = parse_console_uart8250();
+
         if (early_serial_base != 0)
                 early_serial_init(baud);
 }