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
 29struct 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
 37static void __iomem *system_clock __read_mostly;
 38
 39static u64 notrace bcm2835_sched_read(void)
 40{
 41	return readl_relaxed(system_clock);
 42}
 43
 44static 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
 54static 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
 70static 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
133err_iounmap:
134	iounmap(base);
135	return ret;
136}
137TIMER_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
138			bcm2835_timer_init);