ls_uart.c

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/*
 * AVR power-management chip interface for the Buffalo Linkstation /
 * Kurobox Platform.
 *
 * Author: 2006 (c) G. Liakhovetski
 *   [email protected]
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2.  This program is licensed "as is" without any warranty of
 * any kind, whether express or implied.
 */
#include <linux/workqueue.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/serial_reg.h>
#include <linux/serial_8250.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/termbits.h>

#include "mpc10x.h"

static void __iomem *avr_addr;
static unsigned long avr_clock;

static struct work_struct wd_work;

static void wd_stop(struct work_struct *unused)
{
    const char string[] = "AAAAFFFFJJJJ>>>>VVVV>>>>ZZZZVVVVKKKK";
    int i = 0, rescue = 8;
    int len = strlen(string);

    while (rescue--) {
        int j;
        char lsr = in_8(avr_addr + UART_LSR);

        if (lsr & (UART_LSR_THRE | UART_LSR_TEMT)) {
            for (j = 0; j < 16 && i < len; j++, i++)
                out_8(avr_addr + UART_TX, string[i]);
            if (i == len) {
                /* Read "OK" back: 4ms for the last "KKKK"
                   plus a couple bytes back */
                msleep(7);
                printk("linkstation: disarming the AVR watchdog: ");
                while (in_8(avr_addr + UART_LSR) & UART_LSR_DR)
                    printk("%c", in_8(avr_addr + UART_RX));
                break;
            }
        }
        msleep(17);
    }
    printk("\n");
}

#define AVR_QUOT(clock) ((clock) + 8 * 9600) / (16 * 9600)

void avr_uart_configure(void)
{
    unsigned char cval = UART_LCR_WLEN8;
    unsigned int quot = AVR_QUOT(avr_clock);

    if (!avr_addr || !avr_clock)
        return;

    out_8(avr_addr + UART_LCR, cval);           /* initialise UART */
    out_8(avr_addr + UART_MCR, 0);
    out_8(avr_addr + UART_IER, 0);

    cval |= UART_LCR_STOP | UART_LCR_PARITY | UART_LCR_EPAR;

    out_8(avr_addr + UART_LCR, cval);           /* Set character format */

    out_8(avr_addr + UART_LCR, cval | UART_LCR_DLAB);   /* set DLAB */
    out_8(avr_addr + UART_DLL, quot & 0xff);        /* LS of divisor */
    out_8(avr_addr + UART_DLM, quot >> 8);          /* MS of divisor */
    out_8(avr_addr + UART_LCR, cval);           /* reset DLAB */
    out_8(avr_addr + UART_FCR, UART_FCR_ENABLE_FIFO);   /* enable FIFO */
}

void avr_uart_send(const char c)
{
    if (!avr_addr || !avr_clock)
        return;

    out_8(avr_addr + UART_TX, c);
    out_8(avr_addr + UART_TX, c);
    out_8(avr_addr + UART_TX, c);
    out_8(avr_addr + UART_TX, c);
}

static void __init ls_uart_init(void)
{
    local_irq_disable();

#ifndef CONFIG_SERIAL_8250
    out_8(avr_addr + UART_FCR, UART_FCR_ENABLE_FIFO);   /* enable FIFO */
    out_8(avr_addr + UART_FCR, UART_FCR_ENABLE_FIFO |
          UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);   /* clear FIFOs */
    out_8(avr_addr + UART_FCR, 0);
    out_8(avr_addr + UART_IER, 0);

    /* Clear up interrupts */
    (void) in_8(avr_addr + UART_LSR);
    (void) in_8(avr_addr + UART_RX);
    (void) in_8(avr_addr + UART_IIR);
    (void) in_8(avr_addr + UART_MSR);
#endif
    avr_uart_configure();

    local_irq_enable();
}

static int __init ls_uarts_init(void)
{
    struct device_node *avr;
    phys_addr_t phys_addr;
    int len;

    avr = of_find_node_by_path("/soc10x/serial@80004500");
    if (!avr)
        return -EINVAL;

    avr_clock = *(u32*)of_get_property(avr, "clock-frequency", &len);
    phys_addr = ((u32*)of_get_property(avr, "reg", &len))[0];

    if (!avr_clock || !phys_addr)
        return -EINVAL;

    avr_addr = ioremap(phys_addr, 32);
    if (!avr_addr)
        return -EFAULT;

    ls_uart_init();

    INIT_WORK(&wd_work, wd_stop);
    schedule_work(&wd_work);

    return 0;
}

machine_late_initcall(linkstation, ls_uarts_init);