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ls_uart.c

/*
 * AVR power-management chip interface for the Buffalo Linkstation /
 * Kurobox Platform.
 *
 * Author: 2006 (c) G. Liakhovetski
 *     g.liakhovetski@gmx.de
 *
 * 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);

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