sltimers.c

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/***************************************************************************/

/*
 *  sltimers.c -- generic ColdFire slice timer support.
 *
 *  Copyright (C) 2009-2010, Philippe De Muyter <[email protected]>
 *  based on
 *  timers.c -- generic ColdFire hardware timer support.
 *  Copyright (C) 1999-2008, Greg Ungerer <[email protected]>
 */

/***************************************************************************/

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/profile.h>
#include <linux/clocksource.h>
#include <asm/io.h>
#include <asm/traps.h>
#include <asm/machdep.h>
#include <asm/coldfire.h>
#include <asm/mcfslt.h>
#include <asm/mcfsim.h>

/***************************************************************************/

#ifdef CONFIG_HIGHPROFILE

/*
 *  By default use Slice Timer 1 as the profiler clock timer.
 */
#define PA(a)   (MCFSLT_TIMER1 + (a))

/*
 *  Choose a reasonably fast profile timer. Make it an odd value to
 *  try and get good coverage of kernel operations.
 */
#define PROFILEHZ   1013

irqreturn_t mcfslt_profile_tick(int irq, void *dummy)
{
    /* Reset Slice Timer 1 */
    __raw_writel(MCFSLT_SSR_BE | MCFSLT_SSR_TE, PA(MCFSLT_SSR));
    if (current->pid)
        profile_tick(CPU_PROFILING);
    return IRQ_HANDLED;
}

static struct irqaction mcfslt_profile_irq = {
    .name    = "profile timer",
    .flags   = IRQF_DISABLED | IRQF_TIMER,
    .handler = mcfslt_profile_tick,
};

void mcfslt_profile_init(void)
{
    printk(KERN_INFO "PROFILE: lodging TIMER 1 @ %dHz as profile timer\n",
           PROFILEHZ);

    setup_irq(MCF_IRQ_PROFILER, &mcfslt_profile_irq);

    /* Set up TIMER 2 as high speed profile clock */
    __raw_writel(MCF_BUSCLK / PROFILEHZ - 1, PA(MCFSLT_STCNT));
    __raw_writel(MCFSLT_SCR_RUN | MCFSLT_SCR_IEN | MCFSLT_SCR_TEN,
                                PA(MCFSLT_SCR));

}

#endif  /* CONFIG_HIGHPROFILE */

/***************************************************************************/

/*
 *  By default use Slice Timer 0 as the system clock timer.
 */
#define TA(a)   (MCFSLT_TIMER0 + (a))

static u32 mcfslt_cycles_per_jiffy;
static u32 mcfslt_cnt;

static irq_handler_t timer_interrupt;

static irqreturn_t mcfslt_tick(int irq, void *dummy)
{
    /* Reset Slice Timer 0 */
    __raw_writel(MCFSLT_SSR_BE | MCFSLT_SSR_TE, TA(MCFSLT_SSR));
    mcfslt_cnt += mcfslt_cycles_per_jiffy;
    return timer_interrupt(irq, dummy);
}

static struct irqaction mcfslt_timer_irq = {
    .name    = "timer",
    .flags   = IRQF_DISABLED | IRQF_TIMER,
    .handler = mcfslt_tick,
};

static cycle_t mcfslt_read_clk(struct clocksource *cs)
{
    unsigned long flags;
    u32 cycles, scnt;

    local_irq_save(flags);
    scnt = __raw_readl(TA(MCFSLT_SCNT));
    cycles = mcfslt_cnt;
    if (__raw_readl(TA(MCFSLT_SSR)) & MCFSLT_SSR_TE) {
        cycles += mcfslt_cycles_per_jiffy;
        scnt = __raw_readl(TA(MCFSLT_SCNT));
    }
    local_irq_restore(flags);

    /* subtract because slice timers count down */
    return cycles + ((mcfslt_cycles_per_jiffy - 1) - scnt);
}

static struct clocksource mcfslt_clk = {
    .name   = "slt",
    .rating = 250,
    .read   = mcfslt_read_clk,
    .mask   = CLOCKSOURCE_MASK(32),
    .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

void hw_timer_init(irq_handler_t handler)
{
    mcfslt_cycles_per_jiffy = MCF_BUSCLK / HZ;
    /*
     *  The coldfire slice timer (SLT) runs from STCNT to 0 included,
     *  then STCNT again and so on.  It counts thus actually
     *  STCNT + 1 steps for 1 tick, not STCNT.  So if you want
     *  n cycles, initialize STCNT with n - 1.
     */
    __raw_writel(mcfslt_cycles_per_jiffy - 1, TA(MCFSLT_STCNT));
    __raw_writel(MCFSLT_SCR_RUN | MCFSLT_SCR_IEN | MCFSLT_SCR_TEN,
                                TA(MCFSLT_SCR));
    /* initialize mcfslt_cnt knowing that slice timers count down */
    mcfslt_cnt = mcfslt_cycles_per_jiffy;

    timer_interrupt = handler;
    setup_irq(MCF_IRQ_TIMER, &mcfslt_timer_irq);

    clocksource_register_hz(&mcfslt_clk, MCF_BUSCLK);

#ifdef CONFIG_HIGHPROFILE
    mcfslt_profile_init();
#endif
}