2 * linux/arch/arm/kernel/smp_twd.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/clockchips.h>
18 #include <linux/irq.h>
21 #include <asm/smp_twd.h>
22 #include <asm/hardware/gic.h>
24 /* set up by the platform code */
25 void __iomem *twd_base;
27 static unsigned long twd_timer_rate;
29 static void twd_set_mode(enum clock_event_mode mode,
30 struct clock_event_device *clk)
35 case CLOCK_EVT_MODE_PERIODIC:
36 /* timer load already set up */
37 ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
38 | TWD_TIMER_CONTROL_PERIODIC;
40 case CLOCK_EVT_MODE_ONESHOT:
41 /* period set, and timer enabled in 'next_event' hook */
42 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
44 case CLOCK_EVT_MODE_UNUSED:
45 case CLOCK_EVT_MODE_SHUTDOWN:
50 __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
53 static int twd_set_next_event(unsigned long evt,
54 struct clock_event_device *unused)
56 unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
58 ctrl |= TWD_TIMER_CONTROL_ENABLE;
60 __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
61 __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
67 * local_timer_ack: checks for a local timer interrupt.
69 * If a local timer interrupt has occurred, acknowledge and return 1.
70 * Otherwise, return 0.
72 int twd_timer_ack(void)
74 if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
75 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
82 static void __cpuinit twd_calibrate_rate(void)
84 unsigned long load, count;
88 * If this is the first time round, we need to work out how fast
91 if (twd_timer_rate == 0) {
92 printk(KERN_INFO "Calibrating local timer... ");
94 /* Wait for a tick to start */
95 waitjiffies = get_jiffies_64() + 1;
97 while (get_jiffies_64() < waitjiffies)
100 /* OK, now the tick has started, let's get the timer going */
103 /* enable, no interrupt or reload */
104 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
107 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
109 while (get_jiffies_64() < waitjiffies)
112 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
114 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
116 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
117 (twd_timer_rate / 1000000) % 100);
120 load = twd_timer_rate / HZ;
122 __raw_writel(load, twd_base + TWD_TIMER_LOAD);
126 * Setup the local clock events for a CPU.
128 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
130 twd_calibrate_rate();
132 clk->name = "local_timer";
133 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
134 CLOCK_EVT_FEAT_C3STOP;
136 clk->set_mode = twd_set_mode;
137 clk->set_next_event = twd_set_next_event;
139 clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
140 clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
141 clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
143 /* Make sure our local interrupt controller has this enabled */
144 gic_enable_ppi(clk->irq);
146 clockevents_register_device(clk);