2 * linux/arch/arm/mach-realview/localtimer.c
4 * Copyright (C) 2002 ARM Ltd.
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
11 #include <linux/init.h>
12 #include <linux/kernel.h>
13 #include <linux/delay.h>
14 #include <linux/device.h>
15 #include <linux/smp.h>
16 #include <linux/jiffies.h>
17 #include <linux/percpu.h>
18 #include <linux/clockchips.h>
20 #include <asm/mach/time.h>
21 #include <asm/hardware/arm_twd.h>
22 #include <asm/hardware/gic.h>
23 #include <asm/hardware.h>
27 #define TWD_BASE(cpu) (__io_address(REALVIEW_TWD_BASE) + \
28 ((cpu) * REALVIEW_TWD_SIZE))
30 static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
33 * Used on SMP for either the local timer or IPI_TIMER
35 void local_timer_interrupt(void)
37 struct clock_event_device *clk = &__get_cpu_var(local_clockevent);
39 clk->event_handler(clk);
42 #ifdef CONFIG_LOCAL_TIMERS
44 static unsigned long mpcore_timer_rate;
47 * local_timer_ack: checks for a local timer interrupt.
49 * If a local timer interrupt has occurred, acknowledge and return 1.
50 * Otherwise, return 0.
52 int local_timer_ack(void)
54 void __iomem *base = TWD_BASE(smp_processor_id());
56 if (__raw_readl(base + TWD_TIMER_INTSTAT)) {
57 __raw_writel(1, base + TWD_TIMER_INTSTAT);
64 void __cpuinit local_timer_setup(unsigned int cpu)
66 void __iomem *base = TWD_BASE(cpu);
67 unsigned int load, offset;
72 * If this is the first time round, we need to work out how fast
75 if (mpcore_timer_rate == 0) {
76 printk("Calibrating local timer... ");
78 /* Wait for a tick to start */
79 waitjiffies = get_jiffies_64() + 1;
81 while (get_jiffies_64() < waitjiffies)
84 /* OK, now the tick has started, let's get the timer going */
87 /* enable, no interrupt or reload */
88 __raw_writel(0x1, base + TWD_TIMER_CONTROL);
91 __raw_writel(0xFFFFFFFFU, base + TWD_TIMER_COUNTER);
93 while (get_jiffies_64() < waitjiffies)
96 count = __raw_readl(base + TWD_TIMER_COUNTER);
98 mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
100 printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
101 (mpcore_timer_rate / 100000) % 100);
104 load = mpcore_timer_rate / HZ;
106 __raw_writel(load, base + TWD_TIMER_LOAD);
107 __raw_writel(0x7, base + TWD_TIMER_CONTROL);
110 * Now maneuver our local tick into the right part of the jiffy.
111 * Start by working out where within the tick our local timer
112 * interrupt should go.
114 offset = ((mpcore_timer_rate / HZ) / (NR_CPUS + 1)) * (cpu + 1);
117 * gettimeoffset() will return a number of us since the last tick.
118 * Convert this number of us to a local timer tick count.
119 * Be careful of integer overflow whilst keeping maximum precision.
121 * with HZ=100 and 1MHz (fpga) ~ 1GHz processor:
123 * mpcore_timer_rate/10000 = 100 ~ 100,000
125 * so the multiply value will be less than 10^9 always.
127 load = (system_timer->offset() * (mpcore_timer_rate / 10000)) / 100;
129 /* Add on our offset to get the load value */
130 load = (load + offset) % (mpcore_timer_rate / HZ);
132 __raw_writel(load, base + TWD_TIMER_COUNTER);
134 /* Make sure our local interrupt controller has this enabled */
135 __raw_writel(1 << IRQ_LOCALTIMER,
136 __io_address(REALVIEW_GIC_DIST_BASE) + GIC_DIST_ENABLE_SET);
140 * take a local timer down
142 void __cpuexit local_timer_stop(unsigned int cpu)
144 __raw_writel(0, TWD_BASE(cpu) + TWD_TIMER_CONTROL);
147 #else /* CONFIG_LOCAL_TIMERS */
149 static void dummy_timer_set_mode(enum clock_event_mode mode,
150 struct clock_event_device *clk)
154 void __cpuinit local_timer_setup(unsigned int cpu)
156 struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
158 clk->name = "dummy_timer";
159 clk->features = CLOCK_EVT_FEAT_DUMMY;
161 clk->set_mode = dummy_timer_set_mode;
162 clk->broadcast = smp_timer_broadcast;
163 clk->cpumask = cpumask_of_cpu(cpu);
165 clockevents_register_device(clk);
168 #endif /* !CONFIG_LOCAL_TIMERS */