time.c

Go to the documentation of this file.

/*
 *  linux/arch/cris/arch-v32/kernel/time.c
 *
 *  Copyright (C) 2003-2010 Axis Communications AB
 *
 */

#include <linux/timex.h>
#include <linux/time.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/swap.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/threads.h>
#include <linux/cpufreq.h>
#include <asm/types.h>
#include <asm/signal.h>
#include <asm/io.h>
#include <asm/delay.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>

#include <hwregs/reg_map.h>
#include <hwregs/reg_rdwr.h>
#include <hwregs/timer_defs.h>
#include <hwregs/intr_vect_defs.h>
#ifdef CONFIG_CRIS_MACH_ARTPEC3
#include <hwregs/clkgen_defs.h>
#endif

/* Watchdog defines */
#define ETRAX_WD_KEY_MASK   0x7F /* key is 7 bit */
#define ETRAX_WD_HZ     763 /* watchdog counts at 763 Hz */
/* Number of 763 counts before watchdog bites */
#define ETRAX_WD_CNT        ((2*ETRAX_WD_HZ)/HZ + 1)

/* Register the continuos readonly timer available in FS and ARTPEC-3.  */
static cycle_t read_cont_rotime(struct clocksource *cs)
{
    return (u32)REG_RD(timer, regi_timer0, r_time);
}

static struct clocksource cont_rotime = {
    .name   = "crisv32_rotime",
    .rating = 300,
    .read   = read_cont_rotime,
    .mask   = CLOCKSOURCE_MASK(32),
    .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int __init etrax_init_cont_rotime(void)
{
    clocksource_register_khz(&cont_rotime, 100000);
    return 0;
}
arch_initcall(etrax_init_cont_rotime);


unsigned long timer_regs[NR_CPUS] =
{
    regi_timer0,
#ifdef CONFIG_SMP
    regi_timer2
#endif
};

extern int set_rtc_mmss(unsigned long nowtime);

#ifdef CONFIG_CPU_FREQ
static int
cris_time_freq_notifier(struct notifier_block *nb, unsigned long val,
            void *data);

static struct notifier_block cris_time_freq_notifier_block = {
    .notifier_call = cris_time_freq_notifier,
};
#endif

unsigned long get_ns_in_jiffie(void)
{
    reg_timer_r_tmr0_data data;
    unsigned long ns;

    data = REG_RD(timer, regi_timer0, r_tmr0_data);
    ns = (TIMER0_DIV - data) * 10;
    return ns;
}


/* From timer MDS describing the hardware watchdog:
 * 4.3.1 Watchdog Operation
 * The watchdog timer is an 8-bit timer with a configurable start value.
 * Once started the watchdog counts downwards with a frequency of 763 Hz
 * (100/131072 MHz). When the watchdog counts down to 1, it generates an
 * NMI (Non Maskable Interrupt), and when it counts down to 0, it resets the
 * chip.
 */
/* This gives us 1.3 ms to do something useful when the NMI comes */

/* Right now, starting the watchdog is the same as resetting it */
#define start_watchdog reset_watchdog

#if defined(CONFIG_ETRAX_WATCHDOG)
static short int watchdog_key = 42;  /* arbitrary 7 bit number */
#endif

/* Number of pages to consider "out of memory". It is normal that the memory
 * is used though, so set this really low. */
#define WATCHDOG_MIN_FREE_PAGES 8

void reset_watchdog(void)
{
#if defined(CONFIG_ETRAX_WATCHDOG)
    reg_timer_rw_wd_ctrl wd_ctrl = { 0 };

    /* Only keep watchdog happy as long as we have memory left! */
    if(nr_free_pages() > WATCHDOG_MIN_FREE_PAGES) {
        /* Reset the watchdog with the inverse of the old key */
        /* Invert key, which is 7 bits */
        watchdog_key ^= ETRAX_WD_KEY_MASK;
        wd_ctrl.cnt = ETRAX_WD_CNT;
        wd_ctrl.cmd = regk_timer_start;
        wd_ctrl.key = watchdog_key;
        REG_WR(timer, regi_timer0, rw_wd_ctrl, wd_ctrl);
    }
#endif
}

/* stop the watchdog - we still need the correct key */

void stop_watchdog(void)
{
#if defined(CONFIG_ETRAX_WATCHDOG)
    reg_timer_rw_wd_ctrl wd_ctrl = { 0 };
    watchdog_key ^= ETRAX_WD_KEY_MASK; /* invert key, which is 7 bits */
    wd_ctrl.cnt = ETRAX_WD_CNT;
    wd_ctrl.cmd = regk_timer_stop;
    wd_ctrl.key = watchdog_key;
    REG_WR(timer, regi_timer0, rw_wd_ctrl, wd_ctrl);
#endif
}

extern void show_registers(struct pt_regs *regs);

void handle_watchdog_bite(struct pt_regs *regs)
{
#if defined(CONFIG_ETRAX_WATCHDOG)
    extern int cause_of_death;

    oops_in_progress = 1;
    printk(KERN_WARNING "Watchdog bite\n");

    /* Check if forced restart or unexpected watchdog */
    if (cause_of_death == 0xbedead) {
#ifdef CONFIG_CRIS_MACH_ARTPEC3
        /* There is a bug in Artpec-3 (voodoo TR 78) that requires
         * us to go to lower frequency for the reset to be reliable
         */
        reg_clkgen_rw_clk_ctrl ctrl =
            REG_RD(clkgen, regi_clkgen, rw_clk_ctrl);
        ctrl.pll = 0;
        REG_WR(clkgen, regi_clkgen, rw_clk_ctrl, ctrl);
#endif
        while(1);
    }

    /* Unexpected watchdog, stop the watchdog and dump registers. */
    stop_watchdog();
    printk(KERN_WARNING "Oops: bitten by watchdog\n");
    show_registers(regs);
    oops_in_progress = 0;
#ifndef CONFIG_ETRAX_WATCHDOG_NICE_DOGGY
    reset_watchdog();
#endif
    while(1) /* nothing */;
#endif
}

/*
 * timer_interrupt() needs to keep up the real-time clock,
 * as well as call the "xtime_update()" routine every clocktick.
 */
extern void cris_do_profile(struct pt_regs *regs);

static inline irqreturn_t timer_interrupt(int irq, void *dev_id)
{
    struct pt_regs *regs = get_irq_regs();
    int cpu = smp_processor_id();
    reg_timer_r_masked_intr masked_intr;
    reg_timer_rw_ack_intr ack_intr = { 0 };

    /* Check if the timer interrupt is for us (a tmr0 int) */
    masked_intr = REG_RD(timer, timer_regs[cpu], r_masked_intr);
    if (!masked_intr.tmr0)
        return IRQ_NONE;

    /* Acknowledge the timer irq. */
    ack_intr.tmr0 = 1;
    REG_WR(timer, timer_regs[cpu], rw_ack_intr, ack_intr);

    /* Reset watchdog otherwise it resets us! */
    reset_watchdog();

        /* Update statistics. */
    update_process_times(user_mode(regs));

    cris_do_profile(regs); /* Save profiling information */

    /* The master CPU is responsible for the time keeping. */
    if (cpu != 0)
        return IRQ_HANDLED;

    /* Call the real timer interrupt handler */
    xtime_update(1);
        return IRQ_HANDLED;
}

/* Timer is IRQF_SHARED so drivers can add stuff to the timer irq chain.
 * It needs to be IRQF_DISABLED to make the jiffies update work properly.
 */
static struct irqaction irq_timer = {
    .handler = timer_interrupt,
    .flags = IRQF_SHARED | IRQF_DISABLED,
    .name = "timer"
};

void __init cris_timer_init(void)
{
    int cpu = smp_processor_id();
    reg_timer_rw_tmr0_ctrl tmr0_ctrl = { 0 };
    reg_timer_rw_tmr0_div tmr0_div = TIMER0_DIV;
    reg_timer_rw_intr_mask timer_intr_mask;

    /* Setup the etrax timers.
     * Base frequency is 100MHz, divider 1000000 -> 100 HZ
     * We use timer0, so timer1 is free.
     * The trig timer is used by the fasttimer API if enabled.
     */

    tmr0_ctrl.op = regk_timer_ld;
    tmr0_ctrl.freq = regk_timer_f100;
    REG_WR(timer, timer_regs[cpu], rw_tmr0_div, tmr0_div);
    REG_WR(timer, timer_regs[cpu], rw_tmr0_ctrl, tmr0_ctrl); /* Load */
    tmr0_ctrl.op = regk_timer_run;
    REG_WR(timer, timer_regs[cpu], rw_tmr0_ctrl, tmr0_ctrl); /* Start */

    /* Enable the timer irq. */
    timer_intr_mask = REG_RD(timer, timer_regs[cpu], rw_intr_mask);
    timer_intr_mask.tmr0 = 1;
    REG_WR(timer, timer_regs[cpu], rw_intr_mask, timer_intr_mask);
}

void __init time_init(void)
{
    reg_intr_vect_rw_mask intr_mask;

    /* Probe for the RTC and read it if it exists.
     * Before the RTC can be probed the loops_per_usec variable needs
     * to be initialized to make usleep work. A better value for
     * loops_per_usec is calculated by the kernel later once the
     * clock has started.
     */
    loops_per_usec = 50;

    /* Start CPU local timer. */
    cris_timer_init();

    /* Enable the timer irq in global config. */
    intr_mask = REG_RD_VECT(intr_vect, regi_irq, rw_mask, 1);
    intr_mask.timer0 = 1;
    REG_WR_VECT(intr_vect, regi_irq, rw_mask, 1, intr_mask);

    /* Now actually register the timer irq handler that calls
     * timer_interrupt(). */
    setup_irq(TIMER0_INTR_VECT, &irq_timer);

    /* Enable watchdog if we should use one. */

#if defined(CONFIG_ETRAX_WATCHDOG)
    printk(KERN_INFO "Enabling watchdog...\n");
    start_watchdog();

    /* If we use the hardware watchdog, we want to trap it as an NMI
     * and dump registers before it resets us.  For this to happen, we
     * must set the "m" NMI enable flag (which once set, is unset only
     * when an NMI is taken). */
    {
        unsigned long flags;
        local_save_flags(flags);
        flags |= (1<<30); /* NMI M flag is at bit 30 */
        local_irq_restore(flags);
    }
#endif

#ifdef CONFIG_CPU_FREQ
    cpufreq_register_notifier(&cris_time_freq_notifier_block,
        CPUFREQ_TRANSITION_NOTIFIER);
#endif
}

#ifdef CONFIG_CPU_FREQ
static int
cris_time_freq_notifier(struct notifier_block *nb, unsigned long val,
            void *data)
{
    struct cpufreq_freqs *freqs = data;
    if (val == CPUFREQ_POSTCHANGE) {
        reg_timer_r_tmr0_data data;
        reg_timer_rw_tmr0_div div = (freqs->new * 500) / HZ;
        do {
            data = REG_RD(timer, timer_regs[freqs->cpu],
                r_tmr0_data);
        } while (data > 20);
        REG_WR(timer, timer_regs[freqs->cpu], rw_tmr0_div, div);
    }
    return 0;
}
#endif