heartbeat.c

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/*
 * Copyright (C) 2007-2009 Michal Simek <[email protected]>
 * 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 *prop;
    int j;
    const char * const gpio_list[] = {
        "xlnx,xps-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;
    }

    if (gpio) {
        base_addr = be32_to_cpup(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);

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