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Linux/arch/arm/kernel/smp_twd.c

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  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/localtimer.h>
 23 #include <asm/hardware/gic.h>
 24 
 25 /* set up by the platform code */
 26 void __iomem *twd_base;
 27 
 28 static unsigned long twd_timer_rate;
 29 
 30 static struct clock_event_device __percpu **twd_evt;
 31 
 32 static void twd_set_mode(enum clock_event_mode mode,
 33                         struct clock_event_device *clk)
 34 {
 35         unsigned long ctrl;
 36 
 37         switch (mode) {
 38         case CLOCK_EVT_MODE_PERIODIC:
 39                 /* timer load already set up */
 40                 ctrl = TWD_TIMER_CONTROL_ENABLE | TWD_TIMER_CONTROL_IT_ENABLE
 41                         | TWD_TIMER_CONTROL_PERIODIC;
 42                 __raw_writel(twd_timer_rate / HZ, twd_base + TWD_TIMER_LOAD);
 43                 break;
 44         case CLOCK_EVT_MODE_ONESHOT:
 45                 /* period set, and timer enabled in 'next_event' hook */
 46                 ctrl = TWD_TIMER_CONTROL_IT_ENABLE | TWD_TIMER_CONTROL_ONESHOT;
 47                 break;
 48         case CLOCK_EVT_MODE_UNUSED:
 49         case CLOCK_EVT_MODE_SHUTDOWN:
 50         default:
 51                 ctrl = 0;
 52         }
 53 
 54         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
 55 }
 56 
 57 static int twd_set_next_event(unsigned long evt,
 58                         struct clock_event_device *unused)
 59 {
 60         unsigned long ctrl = __raw_readl(twd_base + TWD_TIMER_CONTROL);
 61 
 62         ctrl |= TWD_TIMER_CONTROL_ENABLE;
 63 
 64         __raw_writel(evt, twd_base + TWD_TIMER_COUNTER);
 65         __raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
 66 
 67         return 0;
 68 }
 69 
 70 /*
 71  * local_timer_ack: checks for a local timer interrupt.
 72  *
 73  * If a local timer interrupt has occurred, acknowledge and return 1.
 74  * Otherwise, return 0.
 75  */
 76 int twd_timer_ack(void)
 77 {
 78         if (__raw_readl(twd_base + TWD_TIMER_INTSTAT)) {
 79                 __raw_writel(1, twd_base + TWD_TIMER_INTSTAT);
 80                 return 1;
 81         }
 82 
 83         return 0;
 84 }
 85 
 86 void twd_timer_stop(struct clock_event_device *clk)
 87 {
 88         twd_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
 89         disable_percpu_irq(clk->irq);
 90 }
 91 
 92 static void __cpuinit twd_calibrate_rate(void)
 93 {
 94         unsigned long count;
 95         u64 waitjiffies;
 96 
 97         /*
 98          * If this is the first time round, we need to work out how fast
 99          * the timer ticks
100          */
101         if (twd_timer_rate == 0) {
102                 printk(KERN_INFO "Calibrating local timer... ");
103 
104                 /* Wait for a tick to start */
105                 waitjiffies = get_jiffies_64() + 1;
106 
107                 while (get_jiffies_64() < waitjiffies)
108                         udelay(10);
109 
110                 /* OK, now the tick has started, let's get the timer going */
111                 waitjiffies += 5;
112 
113                                  /* enable, no interrupt or reload */
114                 __raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
115 
116                                  /* maximum value */
117                 __raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
118 
119                 while (get_jiffies_64() < waitjiffies)
120                         udelay(10);
121 
122                 count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
123 
124                 twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
125 
126                 printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
127                         (twd_timer_rate / 10000) % 100);
128         }
129 }
130 
131 static irqreturn_t twd_handler(int irq, void *dev_id)
132 {
133         struct clock_event_device *evt = *(struct clock_event_device **)dev_id;
134 
135         if (twd_timer_ack()) {
136                 evt->event_handler(evt);
137                 return IRQ_HANDLED;
138         }
139 
140         return IRQ_NONE;
141 }
142 
143 /*
144  * Setup the local clock events for a CPU.
145  */
146 void __cpuinit twd_timer_setup(struct clock_event_device *clk)
147 {
148         struct clock_event_device **this_cpu_clk;
149 
150         if (!twd_evt) {
151                 int err;
152 
153                 twd_evt = alloc_percpu(struct clock_event_device *);
154                 if (!twd_evt) {
155                         pr_err("twd: can't allocate memory\n");
156                         return;
157                 }
158 
159                 err = request_percpu_irq(clk->irq, twd_handler,
160                                          "twd", twd_evt);
161                 if (err) {
162                         pr_err("twd: can't register interrupt %d (%d)\n",
163                                clk->irq, err);
164                         return;
165                 }
166         }
167 
168         twd_calibrate_rate();
169 
170         clk->name = "local_timer";
171         clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
172                         CLOCK_EVT_FEAT_C3STOP;
173         clk->rating = 350;
174         clk->set_mode = twd_set_mode;
175         clk->set_next_event = twd_set_next_event;
176         clk->shift = 20;
177         clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
178         clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
179         clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
180 
181         this_cpu_clk = __this_cpu_ptr(twd_evt);
182         *this_cpu_clk = clk;
183 
184         clockevents_register_device(clk);
185 
186         enable_percpu_irq(clk->irq, 0);
187 }
188 

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