2 * Copyright 2012 Simon Arlott
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.
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.
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
19 #include <linux/bcm2835_timer.h>
20 #include <linux/bitops.h>
21 #include <linux/clockchips.h>
22 #include <linux/clocksource.h>
23 #include <linux/interrupt.h>
24 #include <linux/irqreturn.h>
25 #include <linux/kernel.h>
26 #include <linux/module.h>
27 #include <linux/of_address.h>
28 #include <linux/of_irq.h>
29 #include <linux/of_platform.h>
30 #include <linux/slab.h>
31 #include <linux/string.h>
33 #include <asm/sched_clock.h>
36 #define REG_CONTROL 0x00
37 #define REG_COUNTER_LO 0x04
38 #define REG_COUNTER_HI 0x08
39 #define REG_COMPARE(n) (0x0c + (n) * 4)
41 #define DEFAULT_TIMER 3
43 struct bcm2835_timer
{
44 void __iomem
*control
;
45 void __iomem
*compare
;
47 struct clock_event_device evt
;
51 static void __iomem
*system_clock __read_mostly
;
53 static u32 notrace
bcm2835_sched_read(void)
55 return readl_relaxed(system_clock
);
58 static void bcm2835_time_set_mode(enum clock_event_mode mode
,
59 struct clock_event_device
*evt_dev
)
62 case CLOCK_EVT_MODE_ONESHOT
:
63 case CLOCK_EVT_MODE_UNUSED
:
64 case CLOCK_EVT_MODE_SHUTDOWN
:
65 case CLOCK_EVT_MODE_RESUME
:
68 WARN(1, "%s: unhandled event mode %d\n", __func__
, mode
);
73 static int bcm2835_time_set_next_event(unsigned long event
,
74 struct clock_event_device
*evt_dev
)
76 struct bcm2835_timer
*timer
= container_of(evt_dev
,
77 struct bcm2835_timer
, evt
);
78 writel_relaxed(readl_relaxed(system_clock
) + event
,
83 static irqreturn_t
bcm2835_time_interrupt(int irq
, void *dev_id
)
85 struct bcm2835_timer
*timer
= dev_id
;
86 void (*event_handler
)(struct clock_event_device
*);
87 if (readl_relaxed(timer
->control
) & timer
->match_mask
) {
88 writel_relaxed(timer
->match_mask
, timer
->control
);
90 event_handler
= ACCESS_ONCE(timer
->evt
.event_handler
);
92 event_handler(&timer
->evt
);
99 static struct of_device_id bcm2835_time_match
[] __initconst
= {
100 { .compatible
= "brcm,bcm2835-system-timer" },
104 void __init
bcm2835_timer_init(void)
106 struct device_node
*node
;
110 struct bcm2835_timer
*timer
;
112 node
= of_find_matching_node(NULL
, bcm2835_time_match
);
114 panic("No bcm2835 timer node");
116 base
= of_iomap(node
, 0);
118 panic("Can't remap registers");
120 if (of_property_read_u32(node
, "clock-frequency", &freq
))
121 panic("Can't read clock-frequency");
123 system_clock
= base
+ REG_COUNTER_LO
;
124 setup_sched_clock(bcm2835_sched_read
, 32, freq
);
126 clocksource_mmio_init(base
+ REG_COUNTER_LO
, node
->name
,
127 freq
, 300, 32, clocksource_mmio_readl_up
);
129 irq
= irq_of_parse_and_map(node
, DEFAULT_TIMER
);
131 panic("Can't parse IRQ");
133 timer
= kzalloc(sizeof(*timer
), GFP_KERNEL
);
135 panic("Can't allocate timer struct\n");
137 timer
->control
= base
+ REG_CONTROL
;
138 timer
->compare
= base
+ REG_COMPARE(DEFAULT_TIMER
);
139 timer
->match_mask
= BIT(DEFAULT_TIMER
);
140 timer
->evt
.name
= node
->name
;
141 timer
->evt
.rating
= 300;
142 timer
->evt
.features
= CLOCK_EVT_FEAT_ONESHOT
;
143 timer
->evt
.set_mode
= bcm2835_time_set_mode
;
144 timer
->evt
.set_next_event
= bcm2835_time_set_next_event
;
145 timer
->evt
.cpumask
= cpumask_of(0);
146 timer
->act
.name
= node
->name
;
147 timer
->act
.flags
= IRQF_TIMER
| IRQF_SHARED
;
148 timer
->act
.dev_id
= timer
;
149 timer
->act
.handler
= bcm2835_time_interrupt
;
151 if (setup_irq(irq
, &timer
->act
))
152 panic("Can't set up timer IRQ\n");
154 clockevents_config_and_register(&timer
->evt
, freq
, 0xf, 0xffffffff);
156 pr_info("bcm2835: system timer (irq = %d)\n", irq
);