time.c

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/*
 * Copyright (C) 2008-2009 Manuel Lauss <[email protected]>
 *
 * Previous incarnations were:
 * Copyright (C) 2001, 2006, 2008 MontaVista Software, <[email protected]>
 * Copied and modified Carsten Langgaard's time.c
 *
 * Carsten Langgaard, [email protected]
 * Copyright (C) 1999,2000 MIPS Technologies, Inc.  All rights reserved.
 *
 * ########################################################################
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * ########################################################################
 *
 * Clocksource/event using the 32.768kHz-clocked Counter1 ('RTC' in the
 * databooks).  Firmware/Board init code must enable the counters in the
 * counter control register, otherwise the CP0 counter clocksource/event
 * will be installed instead (and use of 'wait' instruction is prohibited).
 */

#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>

#include <asm/processor.h>
#include <asm/time.h>
#include <asm/mach-au1x00/au1000.h>

/* 32kHz clock enabled and detected */
#define CNTR_OK (SYS_CNTRL_E0 | SYS_CNTRL_32S)

static cycle_t au1x_counter1_read(struct clocksource *cs)
{
    return au_readl(SYS_RTCREAD);
}

static struct clocksource au1x_counter1_clocksource = {
    .name       = "alchemy-counter1",
    .read       = au1x_counter1_read,
    .mask       = CLOCKSOURCE_MASK(32),
    .flags      = CLOCK_SOURCE_IS_CONTINUOUS,
    .rating     = 100,
};

static int au1x_rtcmatch2_set_next_event(unsigned long delta,
                     struct clock_event_device *cd)
{
    delta += au_readl(SYS_RTCREAD);
    /* wait for register access */
    while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_M21)
        ;
    au_writel(delta, SYS_RTCMATCH2);
    au_sync();

    return 0;
}

static void au1x_rtcmatch2_set_mode(enum clock_event_mode mode,
                    struct clock_event_device *cd)
{
}

static irqreturn_t au1x_rtcmatch2_irq(int irq, void *dev_id)
{
    struct clock_event_device *cd = dev_id;
    cd->event_handler(cd);
    return IRQ_HANDLED;
}

static struct clock_event_device au1x_rtcmatch2_clockdev = {
    .name       = "rtcmatch2",
    .features   = CLOCK_EVT_FEAT_ONESHOT,
    .rating     = 100,
    .set_next_event = au1x_rtcmatch2_set_next_event,
    .set_mode   = au1x_rtcmatch2_set_mode,
    .cpumask    = cpu_all_mask,
};

static struct irqaction au1x_rtcmatch2_irqaction = {
    .handler    = au1x_rtcmatch2_irq,
    .flags      = IRQF_TIMER,
    .name       = "timer",
    .dev_id     = &au1x_rtcmatch2_clockdev,
};

static int __init alchemy_time_init(unsigned int m2int)
{
    struct clock_event_device *cd = &au1x_rtcmatch2_clockdev;
    unsigned long t;

    au1x_rtcmatch2_clockdev.irq = m2int;

    /* Check if firmware (YAMON, ...) has enabled 32kHz and clock
     * has been detected.  If so install the rtcmatch2 clocksource,
     * otherwise don't bother.  Note that both bits being set is by
     * no means a definite guarantee that the counters actually work
     * (the 32S bit seems to be stuck set to 1 once a single clock-
     * edge is detected, hence the timeouts).
     */
    if (CNTR_OK != (au_readl(SYS_COUNTER_CNTRL) & CNTR_OK))
        goto cntr_err;

    /*
     * setup counter 1 (RTC) to tick at full speed
     */
    t = 0xffffff;
    while ((au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_T1S) && --t)
        asm volatile ("nop");
    if (!t)
        goto cntr_err;

    au_writel(0, SYS_RTCTRIM);  /* 32.768 kHz */
    au_sync();

    t = 0xffffff;
    while ((au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C1S) && --t)
        asm volatile ("nop");
    if (!t)
        goto cntr_err;
    au_writel(0, SYS_RTCWRITE);
    au_sync();

    t = 0xffffff;
    while ((au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C1S) && --t)
        asm volatile ("nop");
    if (!t)
        goto cntr_err;

    /* register counter1 clocksource and event device */
    clocksource_register_hz(&au1x_counter1_clocksource, 32768);

    cd->shift = 32;
    cd->mult = div_sc(32768, NSEC_PER_SEC, cd->shift);
    cd->max_delta_ns = clockevent_delta2ns(0xffffffff, cd);
    cd->min_delta_ns = clockevent_delta2ns(9, cd);  /* ~0.28ms */
    clockevents_register_device(cd);
    setup_irq(m2int, &au1x_rtcmatch2_irqaction);

    printk(KERN_INFO "Alchemy clocksource installed\n");

    return 0;

cntr_err:
    return -1;
}

static void __init alchemy_setup_c0timer(void)
{
    /*
     * MIPS kernel assigns 'au1k_wait' to 'cpu_wait' before this
     * function is called.  Because the Alchemy counters are unusable
     * the C0 timekeeping code is installed and use of the 'wait'
     * instruction must be prohibited, which is done most easily by
     * assigning NULL to cpu_wait.
     */
    cpu_wait = NULL;
    r4k_clockevent_init();
    init_r4k_clocksource();
}

static int alchemy_m2inttab[] __initdata = {
    AU1000_RTC_MATCH2_INT,
    AU1500_RTC_MATCH2_INT,
    AU1100_RTC_MATCH2_INT,
    AU1550_RTC_MATCH2_INT,
    AU1200_RTC_MATCH2_INT,
    AU1300_RTC_MATCH2_INT,
};

void __init plat_time_init(void)
{
    int t;

    t = alchemy_get_cputype();
    if (t == ALCHEMY_CPU_UNKNOWN)
        alchemy_setup_c0timer();
    else if (alchemy_time_init(alchemy_m2inttab[t]))
        alchemy_setup_c0timer();
}