/*
 * 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.,
 *      earlycon=uart8250,io,0x3f8,9600n8
 *      earlycon=uart8250,mmio,0xff5e0000,115200n8
 *      earlycon=uart8250,mmio32,0xff5e0000,115200n8
 * or
 *      console=uart8250,io,0x3f8,9600n8
 *      console=uart8250,mmio,0xff5e0000,115200n8
 *      console=uart8250,mmio32,0xff5e0000,115200n8
 */

#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 <linux/serial_8250.h>
#include <asm/io.h>
#include <asm/serial.h>
#ifdef CONFIG_FIX_EARLYCON_MEM
#include <asm/pgtable.h>
#include <asm/fixmap.h>
#endif

struct early_serial8250_device {
        struct uart_port port;
        char options[16];               /* e.g., 115200n8 */
        unsigned int baud;
};

static struct early_serial8250_device early_device;

static unsigned int __init serial_in(struct uart_port *port, int offset)
{
        switch (port->iotype) {
        case UPIO_MEM:
                return readb(port->membase + offset);
        case UPIO_MEM32:
                return readl(port->membase + (offset << 2));
        case UPIO_PORT:
                return inb(port->iobase + offset);
        default:
                return 0;
        }
}

static void __init serial_out(struct uart_port *port, int offset, int value)
{
        switch (port->iotype) {
        case UPIO_MEM:
                writeb(value, port->membase + offset);
                break;
        case UPIO_MEM32:
                writel(value, port->membase + (offset << 2));
                break;
        case UPIO_PORT:
                outb(value, port->iobase + offset);
                break;
        }
}

#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 serial_putc(struct uart_port *port, int c)
{
        wait_for_xmitr(port);
        serial_out(port, UART_TX, c);
}

static void __init early_serial8250_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);

        uart_console_write(port, s, count, serial_putc);

        /* 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_serial8250_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_serial8250_device *device,
                                                                char *options)
{
        struct uart_port *port = &device->port;
        int mmio, mmio32, length;

        if (!options)
                return -ENODEV;

        port->uartclk = BASE_BAUD * 16;

        mmio = !strncmp(options, "mmio,", 5);
        mmio32 = !strncmp(options, "mmio32,", 7);
        if (mmio || mmio32) {
                port->iotype = (mmio ? UPIO_MEM : UPIO_MEM32);
                port->mapbase = simple_strtoul(options + (mmio ? 5 : 7),
                                               &options, 0);
                if (mmio32)
                        port->regshift = 2;
#ifdef CONFIG_FIX_EARLYCON_MEM
                set_fixmap_nocache(FIX_EARLYCON_MEM_BASE,
                                        port->mapbase & PAGE_MASK);
                port->membase =
                        (void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);
                port->membase += port->mapbase & ~PAGE_MASK;
#else
                port->membase = ioremap_nocache(port->mapbase, 64);
                if (!port->membase) {
                        printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n",
                                __func__,
                               (unsigned long long) port->mapbase);
                        return -ENOMEM;
                }
#endif
        } else if (!strncmp(options, "io,", 3)) {
                port->iotype = UPIO_PORT;
                port->iobase = simple_strtoul(options + 3, &options, 0);
                mmio = 0;
        } else
                return -EINVAL;

        options = strchr(options, ',');
        if (options) {
                options++;
                device->baud = simple_strtoul(options, NULL, 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);
        }

        if (mmio || mmio32)
                printk(KERN_INFO
                       "Early serial console at MMIO%s 0x%llx (options '%s')\n",
                        mmio32 ? "32" : "",
                        (unsigned long long)port->mapbase,
                        device->options);
        else
                printk(KERN_INFO
                      "Early serial console at I/O port 0x%lx (options '%s')\n",
                        port->iobase,
                        device->options);

        return 0;
}

static struct console early_serial8250_console __initdata = {
        .name   = "uart",
        .write  = early_serial8250_write,
        .flags  = CON_PRINTBUFFER | CON_BOOT,
        .index  = -1,
};

static int __init early_serial8250_setup(char *options)
{
        struct early_serial8250_device *device = &early_device;
        int err;

        if (device->port.membase || device->port.iobase)
                return 0;

        err = parse_options(device, options);
        if (err < 0)
                return err;

        init_port(device);
        return 0;
}

int __init setup_early_serial8250_console(char *cmdline)
{
        char *options;
        int err;

        options = strstr(cmdline, "uart8250,");
        if (!options) {
                options = strstr(cmdline, "uart,");
                if (!options)
                        return 0;
        }

        options = strchr(cmdline, ',') + 1;
        err = early_serial8250_setup(options);
        if (err < 0)
                return err;

        register_console(&early_serial8250_console);

        return 0;
}

int serial8250_find_port_for_earlycon(void)
{
        struct early_serial8250_device *device = &early_device;
        struct uart_port *port = &device->port;
        int line;
        int ret;

        if (!device->port.membase && !device->port.iobase)
                return -ENODEV;

        line = serial8250_find_port(port);
        if (line < 0)
                return -ENODEV;

        ret = update_console_cmdline("uart", 8250,
                             "ttyS", line, device->options);
        if (ret < 0)
                ret = update_console_cmdline("uart", 0,
                                     "ttyS", line, device->options);

        return ret;
}

early_param("earlycon", setup_early_serial8250_console);