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         struct irqaction act;
  35 };
  36
  37 static void __iomem *system_clock __read_mostly;
  38
  39 static u64 notrace bcm2835_sched_read(void)
  40 {
  41         return readl_relaxed(system_clock);
  42 }
  43
  44 static int bcm2835_time_set_next_event(unsigned long event,
  45         struct clock_event_device *evt_dev)
  46 {
  47         struct bcm2835_timer *timer = container_of(evt_dev,
  48                 struct bcm2835_timer, evt);
  49         writel_relaxed(readl_relaxed(system_clock) + event,
  50                 timer->compare);
  51         return 0;
  52 }
  53
  54 static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
  55 {
  56         struct bcm2835_timer *timer = dev_id;
  57         void (*event_handler)(struct clock_event_device *);
  58         if (readl_relaxed(timer->control) & timer->match_mask) {
  59                 writel_relaxed(timer->match_mask, timer->control);
  60
  61                 event_handler = READ_ONCE(timer->evt.event_handler);
  62                 if (event_handler)
  63                         event_handler(&timer->evt);
  64                 return IRQ_HANDLED;
  65         } else {
  66                 return IRQ_NONE;
  67         }
  68 }
  69
  70 static int __init bcm2835_timer_init(struct device_node *node)
  71 {
  72         void __iomem *base;
  73         u32 freq;
  74         int irq, ret;
  75         struct bcm2835_timer *timer;
  76
  77         base = of_iomap(node, 0);
  78         if (!base) {
  79                 pr_err("Can't remap registers\n");
  80                 return -ENXIO;
  81         }
  82
  83         ret = of_property_read_u32(node, "clock-frequency", &freq);
  84         if (ret) {
  85                 pr_err("Can't read clock-frequency\n");
  86                 goto err_iounmap;
  87         }
  88
  89         system_clock = base + REG_COUNTER_LO;
  90         sched_clock_register(bcm2835_sched_read, 32, freq);
  91
  92         clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
  93                 freq, 300, 32, clocksource_mmio_readl_up);
  94
  95         irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
  96         if (irq <= 0) {
  97                 pr_err("Can't parse IRQ\n");
  98                 ret = -EINVAL;
  99                 goto err_iounmap;
 100         }
 101
 102         timer = kzalloc(sizeof(*timer), GFP_KERNEL);
 103         if (!timer) {
 104                 ret = -ENOMEM;
 105                 goto err_iounmap;
 106         }
 107
 108         timer->control = base + REG_CONTROL;
 109         timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
 110         timer->match_mask = BIT(DEFAULT_TIMER);
 111         timer->evt.name = node->name;
 112         timer->evt.rating = 300;
 113         timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
 114         timer->evt.set_next_event = bcm2835_time_set_next_event;
 115         timer->evt.cpumask = cpumask_of(0);
 116         timer->act.name = node->name;
 117         timer->act.flags = IRQF_TIMER | IRQF_SHARED;
 118         timer->act.dev_id = timer;
 119         timer->act.handler = bcm2835_time_interrupt;
 120
 121         ret = setup_irq(irq, &timer->act);
 122         if (ret) {
 123                 pr_err("Can't set up timer IRQ\n");
 124                 goto err_iounmap;
 125         }
 126
 127         clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
 128
 129         pr_info("bcm2835: system timer (irq = %d)\n", irq);
 130
 131         return 0;
 132
 133 err_iounmap:
 134         iounmap(base);
 135         return ret;
 136 }
 137 TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
 138                         bcm2835_timer_init);