1/* 2 * linux/arch/arm/kernel/smp_twd.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#include <linux/clockchips.h> 18#include <linux/irq.h> 19#include <linux/io.h> 20 21#include <asm/smp_twd.h> 22#include <asm/hardware/gic.h> 23 24/* set up by the platform code */ 25void __iomem *twd_base; 26 27static unsigned long twd_timer_rate; 28 29static void twd_set_mode(enum clock_event_mode mode, 30 struct clock_event_device *clk) 31{ 32 unsigned long ctrl; 33 34 switch (mode) { 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; 39 break; 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; 43 break; 44 case CLOCK_EVT_MODE_UNUSED: 45 case CLOCK_EVT_MODE_SHUTDOWN: 46 default: 47 ctrl = 0; 48 } 49 50 __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL); 51} 52 53static int twd_set_next_event(unsigned long evt, 54 struct clock_event_device *unused) 55{ 56 unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL); 57 58 ctrl |= TWD_TIMER_CONTROL_ENABLE; 59 60 __raw_writel(evt, twd_base + TWD_TIMER_COUNTER); 61 __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL); 62 63 return 0; 64} 65 66/* 67 * local_timer_ack: checks for a local timer interrupt. 68 * 69 * If a local timer interrupt has occurred, acknowledge and return 1. 70 * Otherwise, return 0. 71 */ 72int twd_timer_ack(void) 73{ 74 if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) { 75 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT); 76 return 1; 77 } 78 79 return 0; 80} 81 82static void __cpuinit twd_calibrate_rate(void) 83{ 84 unsigned long load, count; 85 u64 waitjiffies; 86 87 /* 88 * If this is the first time round, we need to work out how fast 89 * the timer ticks 90 */ 91 if (twd_timer_rate == 0) { 92 printk(KERN_INFO "Calibrating local timer... "); 93 94 /* Wait for a tick to start */ 95 waitjiffies = get_jiffies_64() + 1; 96 97 while (get_jiffies_64() < waitjiffies) 98 udelay(10); 99 100 /* OK, now the tick has started, let's get the timer going */ 101 waitjiffies += 8; 102 103 /* enable, no interrupt or reload */ 104 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL); 105 106 /* maximum value */ 107 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER); 108 109 while (get_jiffies_64() < waitjiffies) 110 udelay(10); 111 112 count = __raw_readl(twd_base + TWD_TIMER_COUNTER); 113 114 twd_timer_rate = ((u64)(0xFFFFFFFFUL - count) * HZ) / 8; 115 116 printk("%lu.%03luMHz.\n", twd_timer_rate / 1000000, 117 (twd_timer_rate / 1000) % 1000); 118 } 119 120 load = twd_timer_rate / HZ; 121 122 __raw_writel(load, twd_base + TWD_TIMER_LOAD); 123} 124 125/* 126 * Setup the local clock events for a CPU. 127 */ 128void __cpuinit twd_timer_setup(struct clock_event_device *clk) 129{ 130 unsigned long flags; 131 132 twd_calibrate_rate(); 133 134 clk->name = "local_timer"; 135 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | 136 CLOCK_EVT_FEAT_C3STOP; 137 clk->rating = 350; 138 clk->set_mode = twd_set_mode; 139 clk->set_next_event = twd_set_next_event; 140 clk->shift = 20; 141 clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift); 142 clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk); 143 clk->min_delta_ns = clockevent_delta2ns(0xf, clk); 144 145 clockevents_register_device(clk); 146 147 /* Make sure our local interrupt controller has this enabled */ 148 local_irq_save(flags); 149 irq_to_desc(clk->irq)->status |= IRQ_NOPROBE; 150 get_irq_chip(clk->irq)->unmask(clk->irq); 151 local_irq_restore(flags); 152} 153 154#ifdef CONFIG_HOTPLUG_CPU 155/* 156 * take a local timer down 157 */ 158void twd_timer_stop(void) 159{ 160 __raw_writel(0, twd_base + TWD_TIMER_CONTROL); 161} 162#endif 163