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