target/linux/mcs814x/files-3.3/arch/arm/mach-mcs814x/timer.c

   1 /*
   2  * Moschip MCS814x timer routines
   3  *
   4  * Copyright (C) 2012, Florian Fainelli <florian@openwrt.org>
   5  *
   6  * Licensed under GPLv2
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/interrupt.h>
  10 #include <linux/time.h>
  11 #include <linux/timex.h>
  12 #include <linux/irq.h>
  13 #include <linux/err.h>
  14 #include <linux/clk.h>
  15 #include <linux/io.h>
  16 #include <linux/of.h>
  17 #include <linux/of_address.h>
  18
  19 #include <asm/mach/time.h>
  20 #include <mach/mcs814x.h>
  21
  22 /* Timer block registers */
  23 #define TIMER_VAL       0x00
  24 #define TIMER_CTL       0x04
  25 #define  TIMER_CTL_EN   0x01
  26 #define  TIMER_CTL_DBG  0x02
  27
  28 static u32 last_reload;
  29 static u32 timer_correct;
  30 static u32 clock_rate;
  31 static u32 timer_reload_value;
  32 static void __iomem *mcs814x_timer_base;
  33
  34 static inline unsigned long ticks2usecs(u32 x)
  35 {
  36         return x / (clock_rate / 1000000);
  37 }
  38
  39 /*
  40  * Returns number of ms since last clock interrupt.  Note that interrupts
  41  * will have been disabled by do_gettimeoffset()
  42  */
  43 static unsigned long mcs814x_gettimeoffset(void)
  44 {
  45         u32 ticks = readl_relaxed(mcs814x_timer_base + TIMER_VAL);
  46
  47         if (ticks < last_reload)
  48                 return ticks2usecs(ticks + (u32)(0xffffffff - last_reload));
  49         else
  50                 return ticks2usecs(ticks - last_reload);
  51 }
  52
  53
  54 static irqreturn_t mcs814x_timer_interrupt(int irq, void *dev_id)
  55 {
  56         u32 count = readl_relaxed(mcs814x_timer_base + TIMER_VAL);
  57
  58         /* take into account delay up to this moment */
  59         last_reload = count + timer_correct + timer_reload_value;
  60
  61         if (last_reload < timer_reload_value) {
  62                 last_reload = timer_reload_value;
  63         } else {
  64                 if (timer_correct == 0)
  65                         timer_correct = readl_relaxed(mcs814x_timer_base + TIMER_VAL) - count;
  66         }
  67         writel_relaxed(last_reload, mcs814x_timer_base + TIMER_VAL);
  68
  69         timer_tick();
  70
  71         return IRQ_HANDLED;
  72 }
  73
  74 static struct irqaction mcs814x_timer_irq = {
  75         .name           = "mcs814x-timer",
  76         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  77         .handler        = mcs814x_timer_interrupt,
  78 };
  79
  80 static struct of_device_id mcs814x_timer_ids[] = {
  81         { .compatible = "moschip,mcs814x-timer" },
  82         { /* sentinel */ },
  83 };
  84
  85 static void __init mcs814x_of_timer_init(void)
  86 {
  87         struct device_node *np;
  88         const unsigned int *intspec;
  89
  90         np = of_find_matching_node(NULL, mcs814x_timer_ids);
  91         if (!np)
  92                 panic("unable to find compatible timer node in dtb");
  93
  94         mcs814x_timer_base = of_iomap(np, 0);
  95         if (!mcs814x_timer_base)
  96                 panic("unable to remap timer cpu registers");
  97
  98         intspec = of_get_property(np, "interrupts", NULL);
  99         if (!intspec)
 100                 panic("no interrupts property for timer");
 101
 102         mcs814x_timer_irq.irq = be32_to_cpup(intspec);
 103 }
 104
 105 static void __init mcs814x_timer_init(void)
 106 {
 107         struct clk *clk;
 108
 109         clk = clk_get_sys("timer0", NULL);
 110         if (IS_ERR_OR_NULL(clk))
 111                 panic("unable to get timer0 clock");
 112
 113         clock_rate = clk_get_rate(clk);
 114
 115         mcs814x_of_timer_init();
 116
 117         pr_info("Timer frequency: %d (kHz)\n", clock_rate / 1000);
 118
 119         timer_reload_value = 0xffffffff - (clock_rate / HZ);
 120
 121         /* disable timer */
 122         writel_relaxed(~TIMER_CTL_EN, mcs814x_timer_base + TIMER_CTL);
 123         writel_relaxed(timer_reload_value, mcs814x_timer_base + TIMER_VAL);
 124         last_reload = timer_reload_value;
 125
 126         setup_irq(mcs814x_timer_irq.irq, &mcs814x_timer_irq);
 127         /* enable timer, stop timer in debug mode */
 128         writel_relaxed(TIMER_CTL_EN | TIMER_CTL_DBG,
 129                 mcs814x_timer_base + TIMER_CTL);
 130 }
 131
 132 struct sys_timer mcs814x_timer = {
 133         .init   = mcs814x_timer_init,
 134         .offset = mcs814x_gettimeoffset,
 135 };