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 */ 25 void __iomem *twd_base; 26 27 static unsigned long twd_timer_rate; 28 29 static 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 __raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD); 40 break; 41 case CLOCK_EVT_MODE_ONESHOT: 42 /* period set, and timer enabled in 'next_event' hook */ 43 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT; 44 break; 45 case CLOCK_EVT_MODE_UNUSED: 46 case CLOCK_EVT_MODE_SHUTDOWN: 47 default: 48 ctrl = 0; 49 } 50 51 __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL); 52 } 53 54 static int twd_set_next_event(unsigned long evt, 55 struct clock_event_device *unused) 56 { 57 unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL); 58 59 ctrl |= TWD_TIMER_CONTROL_ENABLE; 60 61 __raw_writel(evt, twd_base + TWD_TIMER_COUNTER); 62 __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL); 63 64 return 0; 65 } 66 67 /* 68 * local_timer_ack: checks for a local timer interrupt. 69 * 70 * If a local timer interrupt has occurred, acknowledge and return 1. 71 * Otherwise, return 0. 72 */ 73 int twd_timer_ack(void) 74 { 75 if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) { 76 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT); 77 return 1; 78 } 79 80 return 0; 81 } 82 83 static void __cpuinit twd_calibrate_rate(void) 84 { 85 unsigned long count; 86 u64 waitjiffies; 87 88 /* 89 * If this is the first time round, we need to work out how fast 90 * the timer ticks 91 */ 92 if (twd_timer_rate == 0) { 93 printk(KERN_INFO "Calibrating local timer... "); 94 95 /* Wait for a tick to start */ 96 waitjiffies = get_jiffies_64() + 1; 97 98 while (get_jiffies_64() < waitjiffies) 99 udelay(10); 100 101 /* OK, now the tick has started, let's get the timer going */ 102 waitjiffies += 5; 103 104 /* enable, no interrupt or reload */ 105 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL); 106 107 /* maximum value */ 108 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER); 109 110 while (get_jiffies_64() < waitjiffies) 111 udelay(10); 112 113 count = __raw_readl(twd_base + TWD_TIMER_COUNTER); 114 115 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5); 116 117 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000, 118 (twd_timer_rate / 10000) % 100); 119 } 120 } 121 122 /* 123 * Setup the local clock events for a CPU. 124 */ 125 void __cpuinit twd_timer_setup(struct clock_event_device *clk) 126 { 127 twd_calibrate_rate(); 128 129 clk->name = "local_timer"; 130 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | 131 CLOCK_EVT_FEAT_C3STOP; 132 clk->rating = 350; 133 clk->set_mode = twd_set_mode; 134 clk->set_next_event = twd_set_next_event; 135 clk->shift = 20; 136 clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift); 137 clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk); 138 clk->min_delta_ns = clockevent_delta2ns(0xf, clk); 139 140 /* Make sure our local interrupt controller has this enabled */ 141 gic_enable_ppi(clk->irq); 142 143 clockevents_register_device(clk); 144 } 145