1 files changed, 255 insertions, 0 deletions

diff --git a/drivers/serial/8250_early.c b/drivers/serial/8250_early.c
new file mode 100644
index 000000000000..b7a5dd710228
--- /dev/null
+++ b/drivers/serial/8250_early.c
@@ -0,0 +1,255 @@
+/*
+ * Early serial console for 8250/16550 devices
+ *
+ * (c) Copyright 2004 Hewlett-Packard Development Company, L.P.
+ *      Bjorn Helgaas <bjorn.helgaas@hp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Based on the 8250.c serial driver, Copyright (C) 2001 Russell King,
+ * and on early_printk.c by Andi Kleen.
+ *
+ * This is for use before the serial driver has initialized, in
+ * particular, before the UARTs have been discovered and named.
+ * Instead of specifying the console device as, e.g., "ttyS0",
+ * we locate the device directly by its MMIO or I/O port address.
+ *
+ * The user can specify the device directly, e.g.,
+ *      console=uart,io,0x3f8,9600n8
+ *      console=uart,mmio,0xff5e0000,115200n8
+ * or platform code can call early_uart_console_init() to set
+ * the early UART device.
+ *
+ * After the normal serial driver starts, we try to locate the
+ * matching ttyS device and start a console there.
+ */
+
+#include <linux/tty.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+#include <linux/serial.h>
+#include <asm/io.h>
+#include <asm/serial.h>
+
+struct early_uart_device {
+        struct uart_port port;
+        char options[16];               /* e.g., 115200n8 */
+        unsigned int baud;
+};
+
+static struct early_uart_device early_device __initdata;
+static int early_uart_registered __initdata;
+
+static unsigned int __init serial_in(struct uart_port *port, int offset)
+{
+        if (port->iotype == UPIO_MEM)
+                return readb(port->membase + offset);
+        else
+                return inb(port->iobase + offset);
+}
+
+static void __init serial_out(struct uart_port *port, int offset, int value)
+{
+        if (port->iotype == UPIO_MEM)
+                writeb(value, port->membase + offset);
+        else
+                outb(value, port->iobase + offset);
+}
+
+#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
+
+static void __init wait_for_xmitr(struct uart_port *port)
+{
+        unsigned int status;
+
+        for (;;) {
+                status = serial_in(port, UART_LSR);
+                if ((status & BOTH_EMPTY) == BOTH_EMPTY)
+                        return;
+                cpu_relax();
+        }
+}
+
+static void __init putc(struct uart_port *port, unsigned char c)
+{
+        wait_for_xmitr(port);
+        serial_out(port, UART_TX, c);
+}
+
+static void __init early_uart_write(struct console *console, const char *s, unsigned int count)
+{
+        struct uart_port *port = &early_device.port;
+        unsigned int ier;
+
+        /* Save the IER and disable interrupts */
+        ier = serial_in(port, UART_IER);
+        serial_out(port, UART_IER, 0);
+
+        while (*s && count-- > 0) {
+                putc(port, *s);
+                if (*s == '\n')
+                        putc(port, '\r');
+                s++;
+        }
+
+        /* Wait for transmitter to become empty and restore the IER */
+        wait_for_xmitr(port);
+        serial_out(port, UART_IER, ier);
+}
+
+static unsigned int __init probe_baud(struct uart_port *port)
+{
+        unsigned char lcr, dll, dlm;
+        unsigned int quot;
+
+        lcr = serial_in(port, UART_LCR);
+        serial_out(port, UART_LCR, lcr | UART_LCR_DLAB);
+        dll = serial_in(port, UART_DLL);
+        dlm = serial_in(port, UART_DLM);
+        serial_out(port, UART_LCR, lcr);
+
+        quot = (dlm << 8) | dll;
+        return (port->uartclk / 16) / quot;
+}
+
+static void __init init_port(struct early_uart_device *device)
+{
+        struct uart_port *port = &device->port;
+        unsigned int divisor;
+        unsigned char c;
+
+        serial_out(port, UART_LCR, 0x3);        /* 8n1 */
+        serial_out(port, UART_IER, 0);          /* no interrupt */
+        serial_out(port, UART_FCR, 0);          /* no fifo */
+        serial_out(port, UART_MCR, 0x3);        /* DTR + RTS */
+
+        divisor = port->uartclk / (16 * device->baud);
+        c = serial_in(port, UART_LCR);
+        serial_out(port, UART_LCR, c | UART_LCR_DLAB);
+        serial_out(port, UART_DLL, divisor & 0xff);
+        serial_out(port, UART_DLM, (divisor >> 8) & 0xff);
+        serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
+}
+
+static int __init parse_options(struct early_uart_device *device, char *options)
+{
+        struct uart_port *port = &device->port;
+        int mapsize = 64;
+        int mmio, length;
+
+        if (!options)
+                return -ENODEV;
+
+        port->uartclk = BASE_BAUD * 16;
+        if (!strncmp(options, "mmio,", 5)) {
+                port->iotype = UPIO_MEM;
+                port->mapbase = simple_strtoul(options + 5, &options, 0);
+                port->membase = ioremap(port->mapbase, mapsize);
+                if (!port->membase) {
+                        printk(KERN_ERR "%s: Couldn't ioremap 0x%lx\n",
+                                __FUNCTION__, port->mapbase);
+                        return -ENOMEM;
+                }
+                mmio = 1;
+        } else if (!strncmp(options, "io,", 3)) {
+                port->iotype = UPIO_PORT;
+                port->iobase = simple_strtoul(options + 3, &options, 0);
+                mmio = 0;
+        } else
+                return -EINVAL;
+
+        if ((options = strchr(options, ','))) {
+                options++;
+                device->baud = simple_strtoul(options, 0, 0);
+                length = min(strcspn(options, " "), sizeof(device->options));
+                strncpy(device->options, options, length);
+        } else {
+                device->baud = probe_baud(port);
+                snprintf(device->options, sizeof(device->options), "%u",
+                        device->baud);
+        }
+
+        printk(KERN_INFO "Early serial console at %s 0x%lx (options '%s')\n",
+                mmio ? "MMIO" : "I/O port",
+                mmio ? port->mapbase : (unsigned long) port->iobase,
+                device->options);
+        return 0;
+}
+
+static int __init early_uart_setup(struct console *console, char *options)
+{
+        struct early_uart_device *device = &early_device;
+        int err;
+
+        if (device->port.membase || device->port.iobase)
+                return 0;
+
+        if ((err = parse_options(device, options)) < 0)
+                return err;
+
+        init_port(device);
+        return 0;
+}
+
+static struct console early_uart_console __initdata = {
+        .name   = "uart",
+        .write  = early_uart_write,
+        .setup  = early_uart_setup,
+        .flags  = CON_PRINTBUFFER,
+        .index  = -1,
+};
+
+static int __init early_uart_console_init(void)
+{
+        if (!early_uart_registered) {
+                register_console(&early_uart_console);
+                early_uart_registered = 1;
+        }
+        return 0;
+}
+console_initcall(early_uart_console_init);
+
+int __init early_serial_console_init(char *cmdline)
+{
+        char *options;
+        int err;
+
+        options = strstr(cmdline, "console=uart,");
+        if (!options)
+                return -ENODEV;
+
+        options = strchr(cmdline, ',') + 1;
+        if ((err = early_uart_setup(NULL, options)) < 0)
+                return err;
+        return early_uart_console_init();
+}
+
+static int __init early_uart_console_switch(void)
+{
+        struct early_uart_device *device = &early_device;
+        struct uart_port *port = &device->port;
+        int mmio, line;
+
+        if (!(early_uart_console.flags & CON_ENABLED))
+                return 0;
+
+        /* Try to start the normal driver on a matching line.  */
+        mmio = (port->iotype == UPIO_MEM);
+        line = serial8250_start_console(port, device->options);
+        if (line < 0)
+                printk("No ttyS device at %s 0x%lx for console\n",
+                        mmio ? "MMIO" : "I/O port",
+                        mmio ? port->mapbase :
+                            (unsigned long) port->iobase);
+
+        unregister_console(&early_uart_console);
+        if (mmio)
+                iounmap(port->membase);
+
+        return 0;
+}
+late_initcall(early_uart_console_switch);