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 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 53 static 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 */ 72 int 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 82 static 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 += 5; 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 = (0xFFFFFFFFU - count) * (HZ / 5); 115 116 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000, 117 (twd_timer_rate / 100000) % 100); 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 */ 128 void __cpuinit twd_timer_setup(struct clock_event_device *clk) 129 { 130 twd_calibrate_rate(); 131 132 clk->name = "local_timer"; 133 clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT | 134 CLOCK_EVT_FEAT_C3STOP; 135 clk->rating = 350; 136 clk->set_mode = twd_set_mode; 137 clk->set_next_event = twd_set_next_event; 138 clk->shift = 20; 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); 142 143 /* Make sure our local interrupt controller has this enabled */ 144 gic_enable_ppi(clk->irq); 145 146 clockevents_register_device(clk); 147 } 148