time.c

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/*
 * Time related functions for Hexagon architecture
 *
 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 and
 * only version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#include <linux/init.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/ioport.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/module.h>

#include <asm/timer-regs.h>
#include <asm/hexagon_vm.h>

/*
 * For the clocksource we need:
 *  pcycle frequency (600MHz)
 * For the loops_per_jiffy we need:
 *  thread/cpu frequency (100MHz)
 * And for the timer, we need:
 *  sleep clock rate
 */

cycles_t    pcycle_freq_mhz;
cycles_t    thread_freq_mhz;
cycles_t    sleep_clk_freq;

static struct resource rtos_timer_resources[] = {
    {
        .start  = RTOS_TIMER_REGS_ADDR,
        .end    = RTOS_TIMER_REGS_ADDR+PAGE_SIZE-1,
        .flags  = IORESOURCE_MEM,
    },
};

static struct platform_device rtos_timer_device = {
    .name       = "rtos_timer",
    .id     = -1,
    .num_resources  = ARRAY_SIZE(rtos_timer_resources),
    .resource   = rtos_timer_resources,
};

/*  A lot of this stuff should move into a platform specific section.  */
struct adsp_hw_timer_struct {
    u32 match;   /*  Match value  */
    u32 count;
    u32 enable;  /*  [1] - CLR_ON_MATCH_EN, [0] - EN  */
    u32 clear;   /*  one-shot register that clears the count  */
};

/*  Look for "TCX0" for related constants.  */
static __iomem struct adsp_hw_timer_struct *rtos_timer;

static cycle_t timer_get_cycles(struct clocksource *cs)
{
    return (cycle_t) __vmgettime();
}

static struct clocksource hexagon_clocksource = {
    .name       = "pcycles",
    .rating     = 250,
    .read       = timer_get_cycles,
    .mask       = CLOCKSOURCE_MASK(64),
    .flags      = CLOCK_SOURCE_IS_CONTINUOUS,
};

static int set_next_event(unsigned long delta, struct clock_event_device *evt)
{
    /*  Assuming the timer will be disabled when we enter here.  */

    iowrite32(1, &rtos_timer->clear);
    iowrite32(0, &rtos_timer->clear);

    iowrite32(delta, &rtos_timer->match);
    iowrite32(1 << TIMER_ENABLE, &rtos_timer->enable);
    return 0;
}

/*
 * Sets the mode (periodic, shutdown, oneshot, etc) of a timer.
 */
static void set_mode(enum clock_event_mode mode,
    struct clock_event_device *evt)
{
    switch (mode) {
    case CLOCK_EVT_MODE_SHUTDOWN:
        /* XXX implement me */
    default:
        break;
    }
}

#ifdef CONFIG_SMP
/*  Broadcast mechanism  */
static void broadcast(const struct cpumask *mask)
{
    send_ipi(mask, IPI_TIMER);
}
#endif

static struct clock_event_device hexagon_clockevent_dev = {
    .name       = "clockevent",
    .features   = CLOCK_EVT_FEAT_ONESHOT,
    .rating     = 400,
    .irq        = RTOS_TIMER_INT,
    .set_next_event = set_next_event,
    .set_mode   = set_mode,
#ifdef CONFIG_SMP
    .broadcast  = broadcast,
#endif
};

#ifdef CONFIG_SMP
static DEFINE_PER_CPU(struct clock_event_device, clock_events);

void setup_percpu_clockdev(void)
{
    int cpu = smp_processor_id();
    struct clock_event_device *ce_dev = &hexagon_clockevent_dev;
    struct clock_event_device *dummy_clock_dev =
        &per_cpu(clock_events, cpu);

    memcpy(dummy_clock_dev, ce_dev, sizeof(*dummy_clock_dev));
    INIT_LIST_HEAD(&dummy_clock_dev->list);

    dummy_clock_dev->features = CLOCK_EVT_FEAT_DUMMY;
    dummy_clock_dev->cpumask = cpumask_of(cpu);
    dummy_clock_dev->mode = CLOCK_EVT_MODE_UNUSED;

    clockevents_register_device(dummy_clock_dev);
}

/*  Called from smp.c for each CPU's timer ipi call  */
void ipi_timer(void)
{
    int cpu = smp_processor_id();
    struct clock_event_device *ce_dev = &per_cpu(clock_events, cpu);

    ce_dev->event_handler(ce_dev);
}
#endif /* CONFIG_SMP */

static irqreturn_t timer_interrupt(int irq, void *devid)
{
    struct clock_event_device *ce_dev = &hexagon_clockevent_dev;

    iowrite32(0, &rtos_timer->enable);
    ce_dev->event_handler(ce_dev);

    return IRQ_HANDLED;
}

/*  This should also be pulled from devtree  */
static struct irqaction rtos_timer_intdesc = {
    .handler = timer_interrupt,
    .flags = IRQF_TIMER | IRQF_TRIGGER_RISING,
    .name = "rtos_timer"
};

/*
 * time_init_deferred - called by start_kernel to set up timer/clock source
 *
 * Install the IRQ handler for the clock, setup timers.
 * This is done late, as that way, we can use ioremap().
 *
 * This runs just before the delay loop is calibrated, and
 * is used for delay calibration.
 */
void __init time_init_deferred(void)
{
    struct resource *resource = NULL;
    struct clock_event_device *ce_dev = &hexagon_clockevent_dev;
    struct device_node *dn;
    struct resource r;
    int err;

    ce_dev->cpumask = cpu_all_mask;

    if (!resource)
        resource = rtos_timer_device.resource;

    /*  ioremap here means this has to run later, after paging init  */
    rtos_timer = ioremap(resource->start, resource_size(resource));

    if (!rtos_timer) {
        release_mem_region(resource->start, resource_size(resource));
    }
    clocksource_register_khz(&hexagon_clocksource, pcycle_freq_mhz * 1000);

    /*  Note: the sim generic RTOS clock is apparently really 18750Hz  */

    /*
     * Last arg is some guaranteed seconds for which the conversion will
     * work without overflow.
     */
    clockevents_calc_mult_shift(ce_dev, sleep_clk_freq, 4);

    ce_dev->max_delta_ns = clockevent_delta2ns(0x7fffffff, ce_dev);
    ce_dev->min_delta_ns = clockevent_delta2ns(0xf, ce_dev);

#ifdef CONFIG_SMP
    setup_percpu_clockdev();
#endif

    clockevents_register_device(ce_dev);
    setup_irq(ce_dev->irq, &rtos_timer_intdesc);
}

void __init time_init(void)
{
    late_time_init = time_init_deferred;
}

/*
 * This could become parametric or perhaps even computed at run-time,
 * but for now we take the observed simulator jitter.
 */
static long long fudgefactor = 350;  /* Maybe lower if kernel optimized. */

void __udelay(unsigned long usecs)
{
    unsigned long long start = __vmgettime();
    unsigned long long finish = (pcycle_freq_mhz * usecs) - fudgefactor;

    while ((__vmgettime() - start) < finish)
        cpu_relax(); /*  not sure how this improves readability  */
}
EXPORT_SYMBOL(__udelay);