arch/m68k/coldfire/pit.c

   1 /***************************************************************************/
   2
   3 /*
   4  *      pit.c -- Freescale ColdFire PIT timer. Currently this type of
   5  *               hardware timer only exists in the Freescale ColdFire
   6  *               5270/5271, 5282 and 5208 CPUs. No doubt newer ColdFire
   7  *               family members will probably use it too.
   8  *
   9  *      Copyright (C) 1999-2008, Greg Ungerer (gerg@snapgear.com)
  10  *      Copyright (C) 2001-2004, SnapGear Inc. (www.snapgear.com)
  11  */
  12
  13 /***************************************************************************/
  14
  15 #include <linux/kernel.h>
  16 #include <linux/sched.h>
  17 #include <linux/param.h>
  18 #include <linux/init.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/irq.h>
  21 #include <linux/clockchips.h>
  22 #include <asm/machdep.h>
  23 #include <asm/io.h>
  24 #include <asm/coldfire.h>
  25 #include <asm/mcfpit.h>
  26 #include <asm/mcfsim.h>
  27
  28 /***************************************************************************/
  29
  30 /*
  31  *      By default use timer1 as the system clock timer.
  32  */
  33 #define FREQ    ((MCF_CLK / 2) / 64)
  34 #define TA(a)   (MCFPIT_BASE1 + (a))
  35 #define PIT_CYCLES_PER_JIFFY (FREQ / HZ)
  36
  37 static u32 pit_cnt;
  38
  39 /*
  40  * Initialize the PIT timer.
  41  *
  42  * This is also called after resume to bring the PIT into operation again.
  43  */
  44
  45 static int cf_pit_set_periodic(struct clock_event_device *evt)
  46 {
  47         __raw_writew(MCFPIT_PCSR_DISABLE, TA(MCFPIT_PCSR));
  48         __raw_writew(PIT_CYCLES_PER_JIFFY, TA(MCFPIT_PMR));
  49         __raw_writew(MCFPIT_PCSR_EN | MCFPIT_PCSR_PIE |
  50                      MCFPIT_PCSR_OVW | MCFPIT_PCSR_RLD |
  51                      MCFPIT_PCSR_CLK64, TA(MCFPIT_PCSR));
  52         return 0;
  53 }
  54
  55 static int cf_pit_set_oneshot(struct clock_event_device *evt)
  56 {
  57         __raw_writew(MCFPIT_PCSR_DISABLE, TA(MCFPIT_PCSR));
  58         __raw_writew(MCFPIT_PCSR_EN | MCFPIT_PCSR_PIE |
  59                      MCFPIT_PCSR_OVW | MCFPIT_PCSR_CLK64, TA(MCFPIT_PCSR));
  60         return 0;
  61 }
  62
  63 static int cf_pit_shutdown(struct clock_event_device *evt)
  64 {
  65         __raw_writew(MCFPIT_PCSR_DISABLE, TA(MCFPIT_PCSR));
  66         return 0;
  67 }
  68
  69 /*
  70  * Program the next event in oneshot mode
  71  *
  72  * Delta is given in PIT ticks
  73  */
  74 static int cf_pit_next_event(unsigned long delta,
  75                 struct clock_event_device *evt)
  76 {
  77         __raw_writew(delta, TA(MCFPIT_PMR));
  78         return 0;
  79 }
  80
  81 struct clock_event_device cf_pit_clockevent = {
  82         .name                   = "pit",
  83         .features               = CLOCK_EVT_FEAT_PERIODIC |
  84                                   CLOCK_EVT_FEAT_ONESHOT,
  85         .set_state_shutdown     = cf_pit_shutdown,
  86         .set_state_periodic     = cf_pit_set_periodic,
  87         .set_state_oneshot      = cf_pit_set_oneshot,
  88         .set_next_event         = cf_pit_next_event,
  89         .shift                  = 32,
  90         .irq                    = MCF_IRQ_PIT1,
  91 };
  92
  93
  94
  95 /***************************************************************************/
  96
  97 static irqreturn_t pit_tick(int irq, void *dummy)
  98 {
  99         struct clock_event_device *evt = &cf_pit_clockevent;
 100         u16 pcsr;
 101
 102         /* Reset the ColdFire timer */
 103         pcsr = __raw_readw(TA(MCFPIT_PCSR));
 104         __raw_writew(pcsr | MCFPIT_PCSR_PIF, TA(MCFPIT_PCSR));
 105
 106         pit_cnt += PIT_CYCLES_PER_JIFFY;
 107         evt->event_handler(evt);
 108         return IRQ_HANDLED;
 109 }
 110
 111 /***************************************************************************/
 112
 113 static struct irqaction pit_irq = {
 114         .name    = "timer",
 115         .flags   = IRQF_TIMER,
 116         .handler = pit_tick,
 117 };
 118
 119 /***************************************************************************/
 120
 121 static cycle_t pit_read_clk(struct clocksource *cs)
 122 {
 123         unsigned long flags;
 124         u32 cycles;
 125         u16 pcntr;
 126
 127         local_irq_save(flags);
 128         pcntr = __raw_readw(TA(MCFPIT_PCNTR));
 129         cycles = pit_cnt;
 130         local_irq_restore(flags);
 131
 132         return cycles + PIT_CYCLES_PER_JIFFY - pcntr;
 133 }
 134
 135 /***************************************************************************/
 136
 137 static struct clocksource pit_clk = {
 138         .name   = "pit",
 139         .rating = 100,
 140         .read   = pit_read_clk,
 141         .mask   = CLOCKSOURCE_MASK(32),
 142 };
 143
 144 /***************************************************************************/
 145
 146 void hw_timer_init(irq_handler_t handler)
 147 {
 148         cf_pit_clockevent.cpumask = cpumask_of(smp_processor_id());
 149         cf_pit_clockevent.mult = div_sc(FREQ, NSEC_PER_SEC, 32);
 150         cf_pit_clockevent.max_delta_ns =
 151                 clockevent_delta2ns(0xFFFF, &cf_pit_clockevent);
 152         cf_pit_clockevent.min_delta_ns =
 153                 clockevent_delta2ns(0x3f, &cf_pit_clockevent);
 154         clockevents_register_device(&cf_pit_clockevent);
 155
 156         setup_irq(MCF_IRQ_PIT1, &pit_irq);
 157
 158         clocksource_register_hz(&pit_clk, FREQ);
 159 }
 160
 161 /***************************************************************************/