drivers/clocksource/bcm2835_timer.c

   1 /*
   2  * Copyright 2012 Simon Arlott
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17  */
  18
  19 #include <linux/bitops.h>
  20 #include <linux/clockchips.h>
  21 #include <linux/clocksource.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/irqreturn.h>
  24 #include <linux/kernel.h>
  25 #include <linux/module.h>
  26 #include <linux/of_address.h>
  27 #include <linux/of_irq.h>
  28 #include <linux/of_platform.h>
  29 #include <linux/slab.h>
  30 #include <linux/string.h>
  31 #include <linux/sched_clock.h>
  32
  33 #include <asm/irq.h>
  34
  35 #define REG_CONTROL     0x00
  36 #define REG_COUNTER_LO  0x04
  37 #define REG_COUNTER_HI  0x08
  38 #define REG_COMPARE(n)  (0x0c + (n) * 4)
  39 #define MAX_TIMER       3
  40 #define DEFAULT_TIMER   3
  41
  42 struct bcm2835_timer {
  43         void __iomem *control;
  44         void __iomem *compare;
  45         int match_mask;
  46         struct clock_event_device evt;
  47         struct irqaction act;
  48 };
  49
  50 static void __iomem *system_clock __read_mostly;
  51
  52 static u64 notrace bcm2835_sched_read(void)
  53 {
  54         return readl_relaxed(system_clock);
  55 }
  56
  57 static int bcm2835_time_set_next_event(unsigned long event,
  58         struct clock_event_device *evt_dev)
  59 {
  60         struct bcm2835_timer *timer = container_of(evt_dev,
  61                 struct bcm2835_timer, evt);
  62         writel_relaxed(readl_relaxed(system_clock) + event,
  63                 timer->compare);
  64         return 0;
  65 }
  66
  67 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
  68 {
  69         struct bcm2835_timer *timer = dev_id;
  70         void (*event_handler)(struct clock_event_device *);
  71         if (readl_relaxed(timer->control) & timer->match_mask) {
  72                 writel_relaxed(timer->match_mask, timer->control);
  73
  74                 event_handler = ACCESS_ONCE(timer->evt.event_handler);
  75                 if (event_handler)
  76                         event_handler(&timer->evt);
  77                 return IRQ_HANDLED;
  78         } else {
  79                 return IRQ_NONE;
  80         }
  81 }
  82
  83 static void __init bcm2835_timer_init(struct device_node *node)
  84 {
  85         void __iomem *base;
  86         u32 freq;
  87         int irq;
  88         struct bcm2835_timer *timer;
  89
  90         base = of_iomap(node, 0);
  91         if (!base)
  92                 panic("Can't remap registers");
  93
  94         if (of_property_read_u32(node, "clock-frequency", &freq))
  95                 panic("Can't read clock-frequency");
  96
  97         system_clock = base + REG_COUNTER_LO;
  98         sched_clock_register(bcm2835_sched_read, 32, freq);
  99
 100         clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
 101                 freq, 300, 32, clocksource_mmio_readl_up);
 102
 103         irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
 104         if (irq <= 0)
 105                 panic("Can't parse IRQ");
 106
 107         timer = kzalloc(sizeof(*timer), GFP_KERNEL);
 108         if (!timer)
 109                 panic("Can't allocate timer struct\n");
 110
 111         timer->control = base + REG_CONTROL;
 112         timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
 113         timer->match_mask = BIT(DEFAULT_TIMER);
 114         timer->evt.name = node->name;
 115         timer->evt.rating = 300;
 116         timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
 117         timer->evt.set_next_event = bcm2835_time_set_next_event;
 118         timer->evt.cpumask = cpumask_of(0);
 119         timer->act.name = node->name;
 120         timer->act.flags = IRQF_TIMER | IRQF_SHARED;
 121         timer->act.dev_id = timer;
 122         timer->act.handler = bcm2835_time_interrupt;
 123
 124         if (setup_irq(irq, &timer->act))
 125                 panic("Can't set up timer IRQ\n");
 126
 127         clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
 128
 129         pr_info("bcm2835: system timer (irq = %d)\n", irq);
 130 }
 131 CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
 132                         bcm2835_timer_init);