linux/arch/m68k/coldfire/sltimers.c
<<
>>
Prefs
   1// SPDX-License-Identifier: GPL-2.0
   2/***************************************************************************/
   3
   4/*
   5 *      sltimers.c -- generic ColdFire slice timer support.
   6 *
   7 *      Copyright (C) 2009-2010, Philippe De Muyter <phdm@macqel.be>
   8 *      based on
   9 *      timers.c -- generic ColdFire hardware timer support.
  10 *      Copyright (C) 1999-2008, Greg Ungerer <gerg@snapgear.com>
  11 */
  12
  13/***************************************************************************/
  14
  15#include <linux/kernel.h>
  16#include <linux/init.h>
  17#include <linux/sched.h>
  18#include <linux/interrupt.h>
  19#include <linux/irq.h>
  20#include <linux/profile.h>
  21#include <linux/clocksource.h>
  22#include <asm/io.h>
  23#include <asm/traps.h>
  24#include <asm/machdep.h>
  25#include <asm/coldfire.h>
  26#include <asm/mcfslt.h>
  27#include <asm/mcfsim.h>
  28
  29/***************************************************************************/
  30
  31#ifdef CONFIG_HIGHPROFILE
  32
  33/*
  34 *      By default use Slice Timer 1 as the profiler clock timer.
  35 */
  36#define PA(a)   (MCFSLT_TIMER1 + (a))
  37
  38/*
  39 *      Choose a reasonably fast profile timer. Make it an odd value to
  40 *      try and get good coverage of kernel operations.
  41 */
  42#define PROFILEHZ       1013
  43
  44irqreturn_t mcfslt_profile_tick(int irq, void *dummy)
  45{
  46        /* Reset Slice Timer 1 */
  47        __raw_writel(MCFSLT_SSR_BE | MCFSLT_SSR_TE, PA(MCFSLT_SSR));
  48        if (current->pid)
  49                profile_tick(CPU_PROFILING);
  50        return IRQ_HANDLED;
  51}
  52
  53void mcfslt_profile_init(void)
  54{
  55        int ret;
  56
  57        printk(KERN_INFO "PROFILE: lodging TIMER 1 @ %dHz as profile timer\n",
  58               PROFILEHZ);
  59
  60        ret = request_irq(MCF_IRQ_PROFILER, mcfslt_profile_tick, IRQF_TIMER,
  61                          "profile timer", NULL);
  62        if (ret) {
  63                pr_err("Failed to request irq %d (profile timer): %pe\n",
  64                       MCF_IRQ_PROFILER, ERR_PTR(ret));
  65        }
  66
  67        /* Set up TIMER 2 as high speed profile clock */
  68        __raw_writel(MCF_BUSCLK / PROFILEHZ - 1, PA(MCFSLT_STCNT));
  69        __raw_writel(MCFSLT_SCR_RUN | MCFSLT_SCR_IEN | MCFSLT_SCR_TEN,
  70                                                                PA(MCFSLT_SCR));
  71
  72}
  73
  74#endif  /* CONFIG_HIGHPROFILE */
  75
  76/***************************************************************************/
  77
  78/*
  79 *      By default use Slice Timer 0 as the system clock timer.
  80 */
  81#define TA(a)   (MCFSLT_TIMER0 + (a))
  82
  83static u32 mcfslt_cycles_per_jiffy;
  84static u32 mcfslt_cnt;
  85
  86static irqreturn_t mcfslt_tick(int irq, void *dummy)
  87{
  88        /* Reset Slice Timer 0 */
  89        __raw_writel(MCFSLT_SSR_BE | MCFSLT_SSR_TE, TA(MCFSLT_SSR));
  90        mcfslt_cnt += mcfslt_cycles_per_jiffy;
  91        legacy_timer_tick(1);
  92        return IRQ_HANDLED;
  93}
  94
  95static u64 mcfslt_read_clk(struct clocksource *cs)
  96{
  97        unsigned long flags;
  98        u32 cycles, scnt;
  99
 100        local_irq_save(flags);
 101        scnt = __raw_readl(TA(MCFSLT_SCNT));
 102        cycles = mcfslt_cnt;
 103        if (__raw_readl(TA(MCFSLT_SSR)) & MCFSLT_SSR_TE) {
 104                cycles += mcfslt_cycles_per_jiffy;
 105                scnt = __raw_readl(TA(MCFSLT_SCNT));
 106        }
 107        local_irq_restore(flags);
 108
 109        /* subtract because slice timers count down */
 110        return cycles + ((mcfslt_cycles_per_jiffy - 1) - scnt);
 111}
 112
 113static struct clocksource mcfslt_clk = {
 114        .name   = "slt",
 115        .rating = 250,
 116        .read   = mcfslt_read_clk,
 117        .mask   = CLOCKSOURCE_MASK(32),
 118        .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 119};
 120
 121void hw_timer_init(void)
 122{
 123        int r;
 124
 125        mcfslt_cycles_per_jiffy = MCF_BUSCLK / HZ;
 126        /*
 127         *      The coldfire slice timer (SLT) runs from STCNT to 0 included,
 128         *      then STCNT again and so on.  It counts thus actually
 129         *      STCNT + 1 steps for 1 tick, not STCNT.  So if you want
 130         *      n cycles, initialize STCNT with n - 1.
 131         */
 132        __raw_writel(mcfslt_cycles_per_jiffy - 1, TA(MCFSLT_STCNT));
 133        __raw_writel(MCFSLT_SCR_RUN | MCFSLT_SCR_IEN | MCFSLT_SCR_TEN,
 134                                                                TA(MCFSLT_SCR));
 135        /* initialize mcfslt_cnt knowing that slice timers count down */
 136        mcfslt_cnt = mcfslt_cycles_per_jiffy;
 137
 138        r = request_irq(MCF_IRQ_TIMER, mcfslt_tick, IRQF_TIMER, "timer", NULL);
 139        if (r) {
 140                pr_err("Failed to request irq %d (timer): %pe\n", MCF_IRQ_TIMER,
 141                       ERR_PTR(r));
 142        }
 143
 144        clocksource_register_hz(&mcfslt_clk, MCF_BUSCLK);
 145
 146#ifdef CONFIG_HIGHPROFILE
 147        mcfslt_profile_init();
 148#endif
 149}
 150