drivers/clocksource/vt8500_timer.c

   1 /*
   2  *  arch/arm/mach-vt8500/timer.c
   3  *
   4  *  Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
   5  *  Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  20  */
  21
  22 /*
  23  * This file is copied and modified from the original timer.c provided by
  24  * Alexey Charkov. Minor changes have been made for Device Tree Support.
  25  */
  26
  27 #include <linux/io.h>
  28 #include <linux/irq.h>
  29 #include <linux/interrupt.h>
  30 #include <linux/clocksource.h>
  31 #include <linux/clockchips.h>
  32 #include <linux/delay.h>
  33 #include <asm/mach/time.h>
  34
  35 #include <linux/of.h>
  36 #include <linux/of_address.h>
  37 #include <linux/of_irq.h>
  38
  39 #define VT8500_TIMER_OFFSET     0x0100
  40 #define VT8500_TIMER_HZ         3000000
  41 #define TIMER_MATCH_VAL         0x0000
  42 #define TIMER_COUNT_VAL         0x0010
  43 #define TIMER_STATUS_VAL        0x0014
  44 #define TIMER_IER_VAL           0x001c          /* interrupt enable */
  45 #define TIMER_CTRL_VAL          0x0020
  46 #define TIMER_AS_VAL            0x0024          /* access status */
  47 #define TIMER_COUNT_R_ACTIVE    (1 << 5)        /* not ready for read */
  48 #define TIMER_COUNT_W_ACTIVE    (1 << 4)        /* not ready for write */
  49 #define TIMER_MATCH_W_ACTIVE    (1 << 0)        /* not ready for write */
  50
  51 #define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
  52
  53 static void __iomem *regbase;
  54
  55 static cycle_t vt8500_timer_read(struct clocksource *cs)
  56 {
  57         int loops = msecs_to_loops(10);
  58         writel(3, regbase + TIMER_CTRL_VAL);
  59         while ((readl((regbase + TIMER_AS_VAL)) & TIMER_COUNT_R_ACTIVE)
  60                                                 && --loops)
  61                 cpu_relax();
  62         return readl(regbase + TIMER_COUNT_VAL);
  63 }
  64
  65 static struct clocksource clocksource = {
  66         .name           = "vt8500_timer",
  67         .rating         = 200,
  68         .read           = vt8500_timer_read,
  69         .mask           = CLOCKSOURCE_MASK(32),
  70         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  71 };
  72
  73 static int vt8500_timer_set_next_event(unsigned long cycles,
  74                                     struct clock_event_device *evt)
  75 {
  76         int loops = msecs_to_loops(10);
  77         cycle_t alarm = clocksource.read(&clocksource) + cycles;
  78         while ((readl(regbase + TIMER_AS_VAL) & TIMER_MATCH_W_ACTIVE)
  79                                                 && --loops)
  80                 cpu_relax();
  81         writel((unsigned long)alarm, regbase + TIMER_MATCH_VAL);
  82
  83         if ((signed)(alarm - clocksource.read(&clocksource)) <= 16)
  84                 return -ETIME;
  85
  86         writel(1, regbase + TIMER_IER_VAL);
  87
  88         return 0;
  89 }
  90
  91 static int vt8500_shutdown(struct clock_event_device *evt)
  92 {
  93         writel(readl(regbase + TIMER_CTRL_VAL) | 1, regbase + TIMER_CTRL_VAL);
  94         writel(0, regbase + TIMER_IER_VAL);
  95         return 0;
  96 }
  97
  98 static struct clock_event_device clockevent = {
  99         .name                   = "vt8500_timer",
 100         .features               = CLOCK_EVT_FEAT_ONESHOT,
 101         .rating                 = 200,
 102         .set_next_event         = vt8500_timer_set_next_event,
 103         .set_state_shutdown     = vt8500_shutdown,
 104         .set_state_oneshot      = vt8500_shutdown,
 105 };
 106
 107 static irqreturn_t vt8500_timer_interrupt(int irq, void *dev_id)
 108 {
 109         struct clock_event_device *evt = dev_id;
 110         writel(0xf, regbase + TIMER_STATUS_VAL);
 111         evt->event_handler(evt);
 112
 113         return IRQ_HANDLED;
 114 }
 115
 116 static struct irqaction irq = {
 117         .name    = "vt8500_timer",
 118         .flags   = IRQF_TIMER | IRQF_IRQPOLL,
 119         .handler = vt8500_timer_interrupt,
 120         .dev_id  = &clockevent,
 121 };
 122
 123 static void __init vt8500_timer_init(struct device_node *np)
 124 {
 125         int timer_irq;
 126
 127         regbase = of_iomap(np, 0);
 128         if (!regbase) {
 129                 pr_err("%s: Missing iobase description in Device Tree\n",
 130                                                                 __func__);
 131                 return;
 132         }
 133         timer_irq = irq_of_parse_and_map(np, 0);
 134         if (!timer_irq) {
 135                 pr_err("%s: Missing irq description in Device Tree\n",
 136                                                                 __func__);
 137                 return;
 138         }
 139
 140         writel(1, regbase + TIMER_CTRL_VAL);
 141         writel(0xf, regbase + TIMER_STATUS_VAL);
 142         writel(~0, regbase + TIMER_MATCH_VAL);
 143
 144         if (clocksource_register_hz(&clocksource, VT8500_TIMER_HZ))
 145                 pr_err("%s: vt8500_timer_init: clocksource_register failed for %s\n",
 146                                         __func__, clocksource.name);
 147
 148         clockevent.cpumask = cpumask_of(0);
 149
 150         if (setup_irq(timer_irq, &irq))
 151                 pr_err("%s: setup_irq failed for %s\n", __func__,
 152                                                         clockevent.name);
 153         clockevents_config_and_register(&clockevent, VT8500_TIMER_HZ,
 154                                         4, 0xf0000000);
 155 }
 156
 157 CLOCKSOURCE_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);