arch/arm/mach-vt8500/timer.c

   1 /*
   2  *  arch/arm/mach-vt8500/timer.c
   3  *
   4  *  Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 #include <linux/io.h>
  22 #include <linux/irq.h>
  23 #include <linux/interrupt.h>
  24 #include <linux/clocksource.h>
  25 #include <linux/clockchips.h>
  26 #include <linux/delay.h>
  27
  28 #include <asm/mach/time.h>
  29
  30 #include "devices.h"
  31
  32 #define VT8500_TIMER_OFFSET     0x0100
  33 #define TIMER_MATCH_VAL         0x0000
  34 #define TIMER_COUNT_VAL         0x0010
  35 #define TIMER_STATUS_VAL        0x0014
  36 #define TIMER_IER_VAL           0x001c          /* interrupt enable */
  37 #define TIMER_CTRL_VAL          0x0020
  38 #define TIMER_AS_VAL            0x0024          /* access status */
  39 #define TIMER_COUNT_R_ACTIVE    (1 << 5)        /* not ready for read */
  40 #define TIMER_COUNT_W_ACTIVE    (1 << 4)        /* not ready for write */
  41 #define TIMER_MATCH_W_ACTIVE    (1 << 0)        /* not ready for write */
  42 #define VT8500_TIMER_HZ         3000000
  43
  44 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
  45
  46 static void __iomem *regbase;
  47
  48 static cycle_t vt8500_timer_read(struct clocksource *cs)
  49 {
  50         int loops = msecs_to_loops(10);
  51         writel(3, regbase + TIMER_CTRL_VAL);
  52         while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
  53                                                 && --loops)
  54                 cpu_relax();
  55         return readl(regbase + TIMER_COUNT_VAL);
  56 }
  57
  58 struct clocksource clocksource = {
  59         .name           = "vt8500_timer",
  60         .rating         = 200,
  61         .read           = vt8500_timer_read,
  62         .mask           = CLOCKSOURCE_MASK(32),
  63         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  64 };
  65
  66 static int vt8500_timer_set_next_event(unsigned long cycles,
  67                                     struct clock_event_device *evt)
  68 {
  69         int loops = msecs_to_loops(10);
  70         cycle_t alarm = clocksource.read(&clocksource) + cycles;
  71         while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
  72                                                 && --loops)
  73                 cpu_relax();
  74         writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
  75
  76         if ((signed)(alarm - clocksource.read(&clocksource)) <= 16)
  77                 return -ETIME;
  78
  79         writel(1, regbase + TIMER_IER_VAL);
  80
  81         return 0;
  82 }
  83
  84 static void vt8500_timer_set_mode(enum clock_event_mode mode,
  85                               struct clock_event_device *evt)
  86 {
  87         switch (mode) {
  88         case CLOCK_EVT_MODE_RESUME:
  89         case CLOCK_EVT_MODE_PERIODIC:
  90                 break;
  91         case CLOCK_EVT_MODE_ONESHOT:
  92         case CLOCK_EVT_MODE_UNUSED:
  93         case CLOCK_EVT_MODE_SHUTDOWN:
  94                 writel(readl(regbase + TIMER_CTRL_VAL) | 1,
  95                         regbase + TIMER_CTRL_VAL);
  96                 writel(0, regbase + TIMER_IER_VAL);
  97                 break;
  98         }
  99 }
 100
 101 struct clock_event_device clockevent = {
 102         .name           = "vt8500_timer",
 103         .features       = CLOCK_EVT_FEAT_ONESHOT,
 104         .rating         = 200,
 105         .set_next_event = vt8500_timer_set_next_event,
 106         .set_mode       = vt8500_timer_set_mode,
 107 };
 108
 109 static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
 110 {
 111         struct clock_event_device *evt = dev_id;
 112         writel(0xf, regbase + TIMER_STATUS_VAL);
 113         evt->event_handler(evt);
 114
 115         return IRQ_HANDLED;
 116 }
 117
 118 struct irqaction irq = {
 119         .name    = "vt8500_timer",
 120         .flags   = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
 121         .handler = vt8500_timer_interrupt,
 122         .dev_id  = &clockevent,
 123 };
 124
 125 static void __init vt8500_timer_init(void)
 126 {
 127         regbase = ioremap(wmt_pmc_base + VT8500_TIMER_OFFSET, 0x28);
 128         if (!regbase)
 129                 printk(KERN_ERR "vt8500_timer_init: failed to map MMIO registers\n");
 130
 131         writel(1, regbase + TIMER_CTRL_VAL);
 132         writel(0xf, regbase + TIMER_STATUS_VAL);
 133         writel(~0, regbase + TIMER_MATCH_VAL);
 134
 135         if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
 136                 printk(KERN_ERR "vt8500_timer_init: clocksource_register failed for %s\n",
 137                                         clocksource.name);
 138
 139         clockevents_calc_mult_shift(&clockevent, VT8500_TIMER_HZ, 4);
 140
 141         /* copy-pasted from mach-msm; no idea */
 142         clockevent.max_delta_ns =
 143                 clockevent_delta2ns(0xf0000000, &clockevent);
 144         clockevent.min_delta_ns = clockevent_delta2ns(4, &clockevent);
 145         clockevent.cpumask = cpumask_of(0);
 146
 147         if (setup_irq(wmt_timer_irq, &irq))
 148                 printk(KERN_ERR "vt8500_timer_init: setup_irq failed for %s\n",
 149                                         clockevent.name);
 150         clockevents_register_device(&clockevent);
 151 }
 152
 153 struct sys_timer vt8500_timer = {
 154         .init = vt8500_timer_init
 155 };