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authorSimon Arlott <simon@fire.lp0.eu>2012-09-11 00:38:35 -0400
committerStephen Warren <swarren@wwwdotorg.org>2012-09-19 21:08:46 -0400
commitee4af5696720bb5b9de2e3b18be42089bed1e638 (patch)
treedae604e551100648c6bf42a9b4de6a9ca2cd34b7 /drivers/clocksource
parent89214f009c1d38568456dcf997d93977928fe2c3 (diff)
ARM: bcm2835: add system timer
The System Timer peripheral provides four 32-bit timer channels and a single 64-bit free running counter. Each channel has an output compare register, which is compared against the 32 least significant bits of the free running counter values, and generates an interrupt. Timer 3 is used as the Linux timer. The BCM2835 also contains an SP804-based timer module. However, it apparently has significant differences from the standard SP804 IP block, and Broadcom's documentation recommends using the system timer instead. This patch was extracted from git://github.com/lp0/linux.git branch rpi-split as of 2012/09/08, and modified as follows: * s/bcm2708/bcm2835/. * Modified device tree vendor prefix. * Moved to drivers/clocksource/. This looks like the desired location for such code now. * Added DT binding docs. * Moved struct sys_timer bcm2835_timer into time.c to encapsulate it more. * Simplified bcm2835_time_init() to find one matching node and operate on it, rather than looping over all matching nodes. This seems more consistent with other clocksource code. * Simplified bcm2835_time_init() using of_iomap(). * Renamed struct bcm2835_timer.index to match_mask to better represent its purpose. * s/printk(PR_INFO/pr_info(/ Signed-off-by: Chris Boot <bootc@bootc.net> Signed-off-by: Simon Arlott <simon@fire.lp0.eu> Signed-off-by: Dom Cobley <popcornmix@gmail.com> Signed-off-by: Dom Cobley <dc4@broadcom.com> Signed-off-by: Stephen Warren <swarren@wwwdotorg.org> Acked-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'drivers/clocksource')
-rw-r--r--drivers/clocksource/Makefile1
-rw-r--r--drivers/clocksource/bcm2835_timer.c161
2 files changed, 162 insertions, 0 deletions
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index b65d0c56ab35..d496a55f6bb0 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -13,3 +13,4 @@ obj-$(CONFIG_DW_APB_TIMER) += dw_apb_timer.o
13obj-$(CONFIG_DW_APB_TIMER_OF) += dw_apb_timer_of.o 13obj-$(CONFIG_DW_APB_TIMER_OF) += dw_apb_timer_of.o
14obj-$(CONFIG_CLKSRC_DBX500_PRCMU) += clksrc-dbx500-prcmu.o 14obj-$(CONFIG_CLKSRC_DBX500_PRCMU) += clksrc-dbx500-prcmu.o
15obj-$(CONFIG_ARMADA_370_XP_TIMER) += time-armada-370-xp.o 15obj-$(CONFIG_ARMADA_370_XP_TIMER) += time-armada-370-xp.o
16obj-$(CONFIG_ARCH_BCM2835) += bcm2835_timer.o
diff --git a/drivers/clocksource/bcm2835_timer.c b/drivers/clocksource/bcm2835_timer.c
new file mode 100644
index 000000000000..bc19f12c20ce
--- /dev/null
+++ b/drivers/clocksource/bcm2835_timer.c
@@ -0,0 +1,161 @@
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/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>
32
33#include <asm/sched_clock.h>
34#include <asm/irq.h>
35
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)
40#define MAX_TIMER 3
41#define DEFAULT_TIMER 3
42
43struct bcm2835_timer {
44 void __iomem *control;
45 void __iomem *compare;
46 int match_mask;
47 struct clock_event_device evt;
48 struct irqaction act;
49};
50
51static void __iomem *system_clock __read_mostly;
52
53static u32 notrace bcm2835_sched_read(void)
54{
55 return readl_relaxed(system_clock);
56}
57
58static void bcm2835_time_set_mode(enum clock_event_mode mode,
59 struct clock_event_device *evt_dev)
60{
61 switch (mode) {
62 case CLOCK_EVT_MODE_ONESHOT:
63 case CLOCK_EVT_MODE_UNUSED:
64 case CLOCK_EVT_MODE_SHUTDOWN:
65 case CLOCK_EVT_MODE_RESUME:
66 break;
67 default:
68 WARN(1, "%s: unhandled event mode %d\n", __func__, mode);
69 break;
70 }
71}
72
73static int bcm2835_time_set_next_event(unsigned long event,
74 struct clock_event_device *evt_dev)
75{
76 struct bcm2835_timer *timer = container_of(evt_dev,
77 struct bcm2835_timer, evt);
78 writel_relaxed(readl_relaxed(system_clock) + event,
79 timer->compare);
80 return 0;
81}
82
83static irqreturn_t bcm2835_time_interrupt(int irq, void *dev_id)
84{
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);
89
90 event_handler = ACCESS_ONCE(timer->evt.event_handler);
91 if (event_handler)
92 event_handler(&timer->evt);
93 return IRQ_HANDLED;
94 } else {
95 return IRQ_NONE;
96 }
97}
98
99static struct of_device_id bcm2835_time_match[] __initconst = {
100 { .compatible = "brcm,bcm2835-system-timer" },
101 {}
102};
103
104static void __init bcm2835_time_init(void)
105{
106 struct device_node *node;
107 void __iomem *base;
108 u32 freq;
109 int irq;
110 struct bcm2835_timer *timer;
111
112 node = of_find_matching_node(NULL, bcm2835_time_match);
113 if (!node)
114 panic("No bcm2835 timer node");
115
116 base = of_iomap(node, 0);
117 if (!base)
118 panic("Can't remap registers");
119
120 if (of_property_read_u32(node, "clock-frequency", &freq))
121 panic("Can't read clock-frequency");
122
123 system_clock = base + REG_COUNTER_LO;
124 setup_sched_clock(bcm2835_sched_read, 32, freq);
125
126 clocksource_mmio_init(base + REG_COUNTER_LO, node->name,
127 freq, 300, 32, clocksource_mmio_readl_up);
128
129 irq = irq_of_parse_and_map(node, DEFAULT_TIMER);
130 if (irq <= 0)
131 panic("Can't parse IRQ");
132
133 timer = kzalloc(sizeof(*timer), GFP_KERNEL);
134 if (!timer)
135 panic("Can't allocate timer struct\n");
136
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;
150
151 if (setup_irq(irq, &timer->act))
152 panic("Can't set up timer IRQ\n");
153
154 clockevents_config_and_register(&timer->evt, freq, 0xf, 0xffffffff);
155
156 pr_info("bcm2835: system timer (irq = %d)\n", irq);
157}
158
159struct sys_timer bcm2835_timer = {
160 .init = bcm2835_time_init,
161};