arch/m68k/coldfire/sltimers.c

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