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/hardware.h>
  21
  22 /* Timer block registers */
  23 #define TIMER_VAL       0x00
  24 #define TIMER_CTL       0x04
  25
  26 static u32 last_reload;
  27 static u32 timer_correct;
  28 static u32 clock_rate;
  29 static u32 timer_reload_value;
  30 static void __iomem *mcs814x_timer_base;
  31
  32 static inline unsigned long ticks2usecs(u32 x)
  33 {
  34         return x / (clock_rate / 1000000);
  35 }
  36
  37 /*
  38  * Returns number of ms since last clock interrupt.  Note that interrupts
  39  * will have been disabled by do_gettimeoffset()
  40  */
  41 static unsigned long mcs814x_gettimeoffset(void)
  42 {
  43         u32 ticks = __raw_readl(mcs814x_timer_base + TIMER_VAL);
  44
  45         if (ticks < last_reload)
  46                 return ticks2usecs(ticks + (u32)(0xffffffff - last_reload));
  47         else
  48                 return ticks2usecs(ticks - last_reload);
  49 }
  50
  51
  52 static irqreturn_t mcs814x_timer_interrupt(int irq, void *dev_id)
  53 {
  54         u32 count = __raw_readl(mcs814x_timer_base + TIMER_VAL);
  55
  56         /* take into account delay up to this moment */
  57         last_reload = count + timer_correct + timer_reload_value;
  58
  59         if (last_reload < timer_reload_value) {
  60                 last_reload = timer_reload_value;
  61         } else {
  62                 if (timer_correct == 0)
  63                         timer_correct = __raw_readl(mcs814x_timer_base + TIMER_VAL) - count;
  64         }
  65         __raw_writel(last_reload, mcs814x_timer_base + TIMER_VAL);
  66
  67         timer_tick();
  68
  69         return IRQ_HANDLED;
  70 }
  71
  72 static struct irqaction mcs814x_timer_irq = {
  73         .name           = "mcs814x-timer",
  74         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
  75         .handler        = mcs814x_timer_interrupt,
  76 };
  77
  78 static struct of_device_id mcs814x_timer_ids[] = {
  79         { .compatible = "moschip,mcs814x-timer" },
  80         { /* sentinel */ },
  81 };
  82
  83 static void __init mcs814x_of_timer_init(void)
  84 {
  85         struct device_node *np;
  86         const unsigned int *intspec;
  87
  88         np = of_find_matching_node(NULL, mcs814x_timer_ids);
  89         if (!np)
  90                 panic("unable to find compatible timer node in dtb");
  91
  92         mcs814x_timer_base = of_iomap(np, 0);
  93         if (!mcs814x_timer_base)
  94                 panic("unable to remap timer cpu registers");
  95
  96         intspec = of_get_property(np, "interrupts", NULL);
  97         if (!intspec)
  98                 panic("no interrupts property for timer");
  99
 100         mcs814x_timer_irq.irq = be32_to_cpup(intspec);
 101 }
 102
 103 static void __init mcs814x_timer_init(void)
 104 {
 105         struct clk *clk;
 106
 107         clk = clk_get_sys("timer0", NULL);
 108         if (IS_ERR_OR_NULL(clk))
 109                 panic("unable to get timer0 clock");
 110
 111         clock_rate = clk_get_rate(clk);
 112         clk_put(clk);
 113
 114         mcs814x_of_timer_init();
 115
 116         pr_info("Timer frequency: %d (kHz)\n", clock_rate / 1000);
 117
 118         timer_reload_value = 0xffffffff - (clock_rate / HZ);
 119
 120         /* disable timer */
 121         __raw_writel(0, mcs814x_timer_base + TIMER_CTL);
 122         __raw_writel(timer_reload_value, mcs814x_timer_base + TIMER_VAL);
 123         last_reload = timer_reload_value;
 124
 125         setup_irq(mcs814x_timer_irq.irq, &mcs814x_timer_irq);
 126         /* enable timer, stop timer in debug mode */
 127         __raw_writel(0x03, mcs814x_timer_base + TIMER_CTL);
 128 }
 129
 130 struct sys_timer mcs814x_timer = {
 131         .init   = mcs814x_timer_init,
 132         .offset = mcs814x_gettimeoffset,
 133 };