drivers/clocksource/bcm2835_timer.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright 2012 Simon Arlott
   4  */
   5
   6 #include <linux/bitops.h>
   7 #include <linux/clockchips.h>
   8 #include <linux/clocksource.h>
   9 #include <linux/interrupt.h>
  10 #include <linux/irqreturn.h>
  11 #include <linux/kernel.h>
  12 #include <linux/module.h>
  13 #include <linux/of_address.h>
  14 #include <linux/of_irq.h>
  15 #include <linux/of_platform.h>
  16 #include <linux/slab.h>
  17 #include <linux/string.h>
  18 #include <linux/sched_clock.h>
  19
  20 #include <asm/irq.h>
  21
  22 #define REG_CONTROL     0x00
  23 #define REG_COUNTER_LO  0x04
  24 #define REG_COUNTER_HI  0x08
  25 #define REG_COMPARE(n)  (0x0c + (n) * 4)
  26 #define MAX_TIMER       3
  27 #define DEFAULT_TIMER   3
  28
  29 struct bcm2835_timer {
  30         void __iomem *control;
  31         void __iomem *compare;
  32         int match_mask;
  33         struct clock_event_device evt;
  34 };
  35
  36 static void __iomem *system_clock __read_mostly;
  37
  38 static u64 notrace bcm2835_sched_read(void)
  39 {
  40         return readl_relaxed(system_clock);
  41 }
  42
  43 static int bcm2835_time_set_next_event(unsigned long event,
  44         struct clock_event_device *evt_dev)
  45 {
  46         struct bcm2835_timer *timer = container_of(evt_dev,
  47                 struct bcm2835_timer, evt);
  48         writel_relaxed(readl_relaxed(system_clock) + event,
  49                 timer->compare);
  50         return 0;
  51 }
  52
  53 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
  54 {
  55         struct bcm2835_timer *timer = dev_id;
  56         void (*event_handler)(struct clock_event_device *);
  57         if (readl_relaxed(timer->control) & timer->match_mask) {
  58                 writel_relaxed(timer->match_mask, timer->control);
  59
  60                 event_handler = READ_ONCE(timer->evt.event_handler);
  61                 if (event_handler)
  62                         event_handler(&timer->evt);
  63                 return IRQ_HANDLED;
  64         } else {
  65                 return IRQ_NONE;
  66         }
  67 }
  68
  69 static int __init bcm2835_timer_init(struct device_node *node)
  70 {
  71         void __iomem *base;
  72         u32 freq;
  73         int irq, ret;
  74         struct bcm2835_timer *timer;
  75
  76         base = of_iomap(node, 0);
  77         if (!base) {
  78                 pr_err("Can't remap registers\n");
  79                 return -ENXIO;
  80         }
  81
  82         ret = of_property_read_u32(node, "clock-frequency", &freq);
  83         if (ret) {
  84                 pr_err("Can't read clock-frequency\n");
  85                 goto err_iounmap;
  86         }
  87
  88         system_clock = base + REG_COUNTER_LO;
  89         sched_clock_register(bcm2835_sched_read, 32, freq);
  90
  91         clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
  92                 freq, 300, 32, clocksource_mmio_readl_up);
  93
  94         irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
  95         if (irq <= 0) {
  96                 pr_err("Can't parse IRQ\n");
  97                 ret = -EINVAL;
  98                 goto err_iounmap;
  99         }
 100
 101         timer = kzalloc(sizeof(*timer), GFP_KERNEL);
 102         if (!timer) {
 103                 ret = -ENOMEM;
 104                 goto err_iounmap;
 105         }
 106
 107         timer->control = base + REG_CONTROL;
 108         timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
 109         timer->match_mask = BIT(DEFAULT_TIMER);
 110         timer->evt.name = node->name;
 111         timer->evt.rating = 300;
 112         timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
 113         timer->evt.set_next_event = bcm2835_time_set_next_event;
 114         timer->evt.cpumask = cpumask_of(0);
 115
 116         ret = request_irq(irq, bcm2835_time_interrupt, IRQF_TIMER | IRQF_SHARED,
 117                           node->name, timer);
 118         if (ret) {
 119                 pr_err("Can't set up timer IRQ\n");
 120                 goto err_timer_free;
 121         }
 122
 123         clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
 124
 125         pr_info("bcm2835: system timer (irq = %d)\n", irq);
 126
 127         return 0;
 128
 129 err_timer_free:
 130         kfree(timer);
 131
 132 err_iounmap:
 133         iounmap(base);
 134         return ret;
 135 }
 136 TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
 137                         bcm2835_timer_init);