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heartbeat.c

/*
 * Copyright (C) 2007-2009 Michal Simek <monstr@monstr.eu>
 * Copyright (C) 2007-2009 PetaLogix
 * Copyright (C) 2006 Atmark Techno, Inc.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License. See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#include <linux/sched.h>
#include <linux/io.h>

#include <asm/setup.h>
#include <asm/page.h>
#include <asm/prom.h>

static unsigned int base_addr;

void heartbeat(void)
{
      static unsigned int cnt, period, dist;

      if (base_addr) {
            if (cnt == 0 || cnt == dist)
                  out_be32(base_addr, 1);
            else if (cnt == 7 || cnt == dist + 7)
                  out_be32(base_addr, 0);

            if (++cnt > period) {
                  cnt = 0;
                  /*
                   * The hyperbolic function below modifies the heartbeat
                   * period length in dependency of the current (5min)
                   * load. It goes through the points f(0)=126, f(1)=86,
                   * f(5)=51, f(inf)->30.
                   */
                  period = ((672 << FSHIFT) / (5 * avenrun[0] +
                                    (7 << FSHIFT))) + 30;
                  dist = period / 4;
            }
      }
}

void setup_heartbeat(void)
{
      struct device_node *gpio = NULL;
      int j;
      char *gpio_list[] = {
                        "xlnx,xps-gpio-1.00.a",
                        "xlnx,opb-gpio-1.00.a",
                        NULL
                  };

      for (j = 0; gpio_list[j] != NULL; j++) {
            gpio = of_find_compatible_node(NULL, NULL, gpio_list[j]);
            if (gpio)
                  break;
      }

      base_addr = *(int *) of_get_property(gpio, "reg", NULL);
      base_addr = (unsigned long) ioremap(base_addr, PAGE_SIZE);
      printk(KERN_NOTICE "Heartbeat GPIO at 0x%x\n", base_addr);

      if (*(int *) of_get_property(gpio, "xlnx,is-bidir", NULL))
            out_be32(base_addr + 4, 0); /* GPIO is configured as output */
}

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