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
 42struct 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
 50static void __iomem *system_clock __read_mostly;
 51
 52static u64 notrace bcm2835_sched_read(void)
 53{
 54	return readl_relaxed(system_clock);
 55}
 56
 57static void bcm2835_time_set_mode(enum clock_event_mode mode,
 58	struct clock_event_device *evt_dev)
 59{
 60	switch (mode) {
 61	case CLOCK_EVT_MODE_ONESHOT:
 62	case CLOCK_EVT_MODE_UNUSED:
 63	case CLOCK_EVT_MODE_SHUTDOWN:
 64	case CLOCK_EVT_MODE_RESUME:
 65		break;
 66	default:
 67		WARN(1, "%s: unhandled event mode %d\n", __func__, mode);
 68		break;
 69	}
 70}
 71
 72static int bcm2835_time_set_next_event(unsigned long event,
 73	struct clock_event_device *evt_dev)
 74{
 75	struct bcm2835_timer *timer = container_of(evt_dev,
 76		struct bcm2835_timer, evt);
 77	writel_relaxed(readl_relaxed(system_clock) + event,
 78		timer->compare);
 79	return 0;
 80}
 81
 82static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
 83{
 84	struct bcm2835_timer *timer = dev_id;
 85	void (*event_handler)(struct clock_event_device *);
 86	if (readl_relaxed(timer->control) & timer->match_mask) {
 87		writel_relaxed(timer->match_mask, timer->control);
 88
 89		event_handler = ACCESS_ONCE(timer->evt.event_handler);
 90		if (event_handler)
 91			event_handler(&timer->evt);
 92		return IRQ_HANDLED;
 93	} else {
 94		return IRQ_NONE;
 95	}
 96}
 97
 98static void __init bcm2835_timer_init(struct device_node *node)
 99{
100	void __iomem *base;
101	u32 freq;
102	int irq;
103	struct bcm2835_timer *timer;
104
105	base = of_iomap(node, 0);
106	if (!base)
107		panic("Can't remap registers");
108
109	if (of_property_read_u32(node, "clock-frequency", &freq))
110		panic("Can't read clock-frequency");
111
112	system_clock = base + REG_COUNTER_LO;
113	sched_clock_register(bcm2835_sched_read, 32, freq);
114
115	clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
116		freq, 300, 32, clocksource_mmio_readl_up);
117
118	irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
119	if (irq <= 0)
120		panic("Can't parse IRQ");
121
122	timer = kzalloc(sizeof(*timer), GFP_KERNEL);
123	if (!timer)
124		panic("Can't allocate timer struct\n");
125
126	timer->control = base + REG_CONTROL;
127	timer->compare = base + REG_COMPARE(DEFAULT_TIMER);
128	timer->match_mask = BIT(DEFAULT_TIMER);
129	timer->evt.name = node->name;
130	timer->evt.rating = 300;
131	timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
132	timer->evt.set_mode = bcm2835_time_set_mode;
133	timer->evt.set_next_event = bcm2835_time_set_next_event;
134	timer->evt.cpumask = cpumask_of(0);
135	timer->act.name = node->name;
136	timer->act.flags = IRQF_TIMER | IRQF_SHARED;
137	timer->act.dev_id = timer;
138	timer->act.handler = bcm2835_time_interrupt;
139
140	if (setup_irq(irq, &timer->act))
141		panic("Can't set up timer IRQ\n");
142
143	clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
144
145	pr_info("bcm2835: system timer (irq = %d)\n", irq);
146}
147CLOCKSOURCE_OF_DECLARE(bcm2835, "brcm,bcm2835-system-timer",
148			bcm2835_timer_init);