1 files changed, 139 insertions, 0 deletions

diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
new file mode 100644
index 000000000000..030f4b93e255
--- /dev/null
+++ b/arch/x86/boot/early_serial_console.c
@@ -0,0 +1,139 @@
+#include "boot.h"
+
+#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */
+
+#define XMTRDY          0x20
+
+#define DLAB            0x80
+
+#define TXR             0       /*  Transmit register (WRITE) */
+#define RXR             0       /*  Receive register  (READ)  */
+#define IER             1       /*  Interrupt Enable          */
+#define IIR             2       /*  Interrupt ID              */
+#define FCR             2       /*  FIFO control              */
+#define LCR             3       /*  Line control              */
+#define MCR             4       /*  Modem control             */
+#define LSR             5       /*  Line Status               */
+#define MSR             6       /*  Modem Status              */
+#define DLL             0       /*  Divisor Latch Low         */
+#define DLH             1       /*  Divisor latch High        */
+
+#define DEFAULT_BAUD 9600
+
+static void early_serial_init(int port, int baud)
+{
+        unsigned char c;
+        unsigned divisor;
+
+        outb(0x3, port + LCR);  /* 8n1 */
+        outb(0, port + IER);    /* no interrupt */
+        outb(0, port + FCR);    /* no fifo */
+        outb(0x3, port + MCR);  /* DTR + RTS */
+
+        divisor = 115200 / baud;
+        c = inb(port + LCR);
+        outb(c | DLAB, port + LCR);
+        outb(divisor & 0xff, port + DLL);
+        outb((divisor >> 8) & 0xff, port + DLH);
+        outb(c & ~DLAB, port + LCR);
+
+        early_serial_base = port;
+}
+
+static void parse_earlyprintk(void)
+{
+        int baud = DEFAULT_BAUD;
+        char arg[32];
+        int pos = 0;
+        int port = 0;
+
+        if (cmdline_find_option("earlyprintk", arg, sizeof arg) > 0) {
+                char *e;
+
+                if (!strncmp(arg, "serial", 6)) {
+                        port = DEFAULT_SERIAL_PORT;
+                        pos += 6;
+                }
+
+                if (arg[pos] == ',')
+                        pos++;
+
+                if (!strncmp(arg, "ttyS", 4)) {
+                        static const int bases[] = { 0x3f8, 0x2f8 };
+                        int idx = 0;
+
+                        if (!strncmp(arg + pos, "ttyS", 4))
+                                pos += 4;
+
+                        if (arg[pos++] == '1')
+                                idx = 1;
+
+                        port = bases[idx];
+                }
+
+                if (arg[pos] == ',')
+                        pos++;
+
+                baud = simple_strtoull(arg + pos, &e, 0);
+                if (baud == 0 || arg + pos == e)
+                        baud = DEFAULT_BAUD;
+        }
+
+        if (port)
+                early_serial_init(port, 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 void parse_console_uart8250(void)
+{
+        char optstr[64], *options;
+        int baud = DEFAULT_BAUD;
+        int port = 0;
+
+        /*
+         * console=uart8250,io,0x3f8,115200n8
+         * need to make sure it is last one console !
+         */
+        if (cmdline_find_option("console", optstr, sizeof optstr) <= 0)
+                return;
+
+        options = optstr;
+
+        if (!strncmp(options, "uart8250,io,", 12))
+                port = simple_strtoull(options + 12, &options, 0);
+        else if (!strncmp(options, "uart,io,", 8))
+                port = simple_strtoull(options + 8, &options, 0);
+        else
+                return;
+
+        if (options && (options[0] == ','))
+                baud = simple_strtoull(options + 1, &options, 0);
+        else
+                baud = probe_baud(port);
+
+        if (port)
+                early_serial_init(port, baud);
+}
+
+void console_init(void)
+{
+        parse_earlyprintk();
+
+        if (!early_serial_base)
+                parse_console_uart8250();
+}