target/linux/mcs814x/files-3.18/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 #include <linux/of_irq.h>
  19
  20 #include <asm/mach/time.h>
  21 #include <mach/mcs814x.h>
  22
  23 /* Timer block registers */
  24 #define TIMER_VAL       0x00
  25 #define TIMER_CTL       0x04
  26 #define  TIMER_CTL_EN   0x01
  27 #define  TIMER_CTL_DBG  0x02
  28
  29 static u32 last_reload;
  30 static u32 timer_correct;
  31 static u32 clock_rate;
  32 static u32 timer_reload_value;
  33 static void __iomem *mcs814x_timer_base;
  34
  35 static inline u32 ticks2usecs(u32 x)
  36 {
  37         return x / (clock_rate / 1000000);
  38 }
  39
  40 /*
  41  * Returns number of ms since last clock interrupt.  Note that interrupts
  42  * will have been disabled by do_gettimeoffset()
  43  */
  44 static u32 mcs814x_gettimeoffset(void)
  45 {
  46         u32 ticks = readl_relaxed(mcs814x_timer_base + TIMER_VAL);
  47
  48         if (ticks < last_reload)
  49                 return ticks2usecs(ticks + (u32)(0xffffffff - last_reload));
  50         else
  51                 return ticks2usecs(ticks - last_reload);
  52 }
  53
  54
  55 static irqreturn_t mcs814x_timer_interrupt(int irq, void *dev_id)
  56 {
  57         u32 count = readl_relaxed(mcs814x_timer_base + TIMER_VAL);
  58
  59         /* take into account delay up to this moment */
  60         last_reload = count + timer_correct + timer_reload_value;
  61
  62         if (last_reload < timer_reload_value) {
  63                 last_reload = timer_reload_value;
  64         } else {
  65                 if (timer_correct == 0)
  66                         timer_correct = readl_relaxed(mcs814x_timer_base + TIMER_VAL) - count;
  67         }
  68         writel_relaxed(last_reload, mcs814x_timer_base + TIMER_VAL);
  69
  70         timer_tick();
  71
  72         return IRQ_HANDLED;
  73 }
  74
  75 static struct of_device_id mcs814x_timer_ids[] = {
  76         { .compatible = "moschip,mcs814x-timer" },
  77         { /* sentinel */ },
  78 };
  79
  80 static int __init mcs814x_of_timer_init(void)
  81 {
  82         struct device_node *np;
  83         int irq;
  84
  85         np = of_find_matching_node(NULL, mcs814x_timer_ids);
  86         if (!np)
  87                 panic("unable to find compatible timer node in dtb");
  88
  89         mcs814x_timer_base = of_iomap(np, 0);
  90         if (!mcs814x_timer_base)
  91                 panic("unable to remap timer cpu registers");
  92
  93         irq = irq_of_parse_and_map(np, 0);
  94         if (!irq)
  95                 panic("no interrupts property/mapping failed for timer");
  96
  97         return irq;
  98 }
  99
 100 void __init mcs814x_timer_init(void)
 101 {
 102         struct clk *clk;
 103         int irq;
 104
 105         arch_gettimeoffset = mcs814x_gettimeoffset;
 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
 113         irq = mcs814x_of_timer_init();
 114
 115         pr_info("Timer frequency: %d (kHz)\n", clock_rate / 1000);
 116
 117         timer_reload_value = 0xffffffff - (clock_rate / HZ);
 118
 119         /* disable timer */
 120         writel_relaxed(~TIMER_CTL_EN, mcs814x_timer_base + TIMER_CTL);
 121         writel_relaxed(timer_reload_value, mcs814x_timer_base + TIMER_VAL);
 122         last_reload = timer_reload_value;
 123
 124         if (request_irq(irq, mcs814x_timer_interrupt,
 125                 IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
 126                 "mcs814x-timer", NULL))
 127                 panic("unable to request timer0 irq %d", irq);
 128
 129         /* enable timer, stop timer in debug mode */
 130         writel_relaxed(TIMER_CTL_EN | TIMER_CTL_DBG,
 131                 mcs814x_timer_base + TIMER_CTL);
 132 }