1/*
2 *  linux/arch/arm/mach-realview/localtimer.c
3 *
4 *  Copyright (C) 2002 ARM Ltd.
5 *  All Rights Reserved
6 *
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.
10 */
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
18#include <asm/mach/time.h>
19#include <asm/hardware/arm_twd.h>
20#include <asm/hardware/gic.h>
21#include <asm/hardware.h>
22#include <asm/io.h>
23#include <asm/irq.h>
24
25#define TWD_BASE(cpu)	(__io_address(REALVIEW_TWD_BASE) + \
26			 ((cpu) * REALVIEW_TWD_SIZE))
27
28static unsigned long mpcore_timer_rate;
29
30/*
31 * local_timer_ack: checks for a local timer interrupt.
32 *
33 * If a local timer interrupt has occurred, acknowledge and return 1.
34 * Otherwise, return 0.
35 */
36int local_timer_ack(void)
37{
38	void __iomem *base = TWD_BASE(smp_processor_id());
39
40	if (__raw_readl(base + TWD_TIMER_INTSTAT)) {
41		__raw_writel(1, base + TWD_TIMER_INTSTAT);
42		return 1;
43	}
44
45	return 0;
46}
47
48void __cpuinit local_timer_setup(unsigned int cpu)
49{
50	void __iomem *base = TWD_BASE(cpu);
51	unsigned int load, offset;
52	u64 waitjiffies;
53	unsigned int count;
54
55	/*
56	 * If this is the first time round, we need to work out how fast
57	 * the timer ticks
58	 */
59	if (mpcore_timer_rate == 0) {
60		printk("Calibrating local timer... ");
61
62		/* Wait for a tick to start */
63		waitjiffies = get_jiffies_64() + 1;
64
65		while (get_jiffies_64() < waitjiffies)
66			udelay(10);
67
68		/* OK, now the tick has started, let's get the timer going */
69		waitjiffies += 5;
70
71				 /* enable, no interrupt or reload */
72		__raw_writel(0x1, base + TWD_TIMER_CONTROL);
73
74				 /* maximum value */
75		__raw_writel(0xFFFFFFFFU, base + TWD_TIMER_COUNTER);
76
77		while (get_jiffies_64() < waitjiffies)
78			udelay(10);
79
80		count = __raw_readl(base + TWD_TIMER_COUNTER);
81
82		mpcore_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
83
84		printk("%lu.%02luMHz.\n", mpcore_timer_rate / 1000000,
85			(mpcore_timer_rate / 100000) % 100);
86	}
87
88	load = mpcore_timer_rate / HZ;
89
90	__raw_writel(load, base + TWD_TIMER_LOAD);
91	__raw_writel(0x7,  base + TWD_TIMER_CONTROL);
92
93	/*
94	 * Now maneuver our local tick into the right part of the jiffy.
95	 * Start by working out where within the tick our local timer
96	 * interrupt should go.
97	 */
98	offset = ((mpcore_timer_rate / HZ) / (NR_CPUS + 1)) * (cpu + 1);
99
100	/*
101	 * gettimeoffset() will return a number of us since the last tick.
102	 * Convert this number of us to a local timer tick count.
103	 * Be careful of integer overflow whilst keeping maximum precision.
104	 *
105	 * with HZ=100 and 1MHz (fpga) ~ 1GHz processor:
106	 * load = 1 ~ 10,000
107	 * mpcore_timer_rate/10000 = 100 ~ 100,000
108	 *
109	 * so the multiply value will be less than 10^9 always.
110	 */
111	load = (system_timer->offset() * (mpcore_timer_rate / 10000)) / 100;
112
113	/* Add on our offset to get the load value */
114	load = (load + offset) % (mpcore_timer_rate / HZ);
115
116	__raw_writel(load, base + TWD_TIMER_COUNTER);
117
118	/* Make sure our local interrupt controller has this enabled */
119	__raw_writel(1 << IRQ_LOCALTIMER,
120		     __io_address(REALVIEW_GIC_DIST_BASE) + GIC_DIST_ENABLE_SET);
121}
122
123/*
124 * take a local timer down
125 */
126void __cpuexit local_timer_stop(unsigned int cpu)
127{
128	__raw_writel(0, TWD_BASE(cpu) + TWD_TIMER_CONTROL);
129}
130