arch/arm/mach-realview/localtimer.c

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