LXR uboot/arch/arm/cpu/arm920t/ep93xx/timer.c

   1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * Cirrus Logic EP93xx timer support.
   4 *
   5 * Copyright (C) 2009, 2010 Matthias Kaehlcke <matthias@kaehlcke.net>
   6 *
   7 * Copyright (C) 2004, 2005
   8 * Cory T. Tusar, Videon Central, Inc., <ctusar@videon-central.com>
   9 *
  10 * Based on the original intr.c Cirrus Logic EP93xx Rev D. interrupt support,
  11 * author unknown.
  12 */
  13
  14#include <common.h>
  15#include <init.h>
  16#include <time.h>
  17#include <linux/delay.h>
  18#include <linux/types.h>
  19#include <asm/arch/ep93xx.h>
  20#include <asm/io.h>
  21#include <div64.h>
  22
  23#define TIMER_CLKSEL    (1 << 3)
  24#define TIMER_ENABLE    (1 << 7)
  25
  26#define TIMER_FREQ                      508469          /* ticks / second */
  27#define TIMER_MAX_VAL                   0xFFFFFFFF
  28
  29static struct ep93xx_timer
  30{
  31        unsigned long long ticks;
  32        unsigned long last_read;
  33} timer;
  34
  35static inline unsigned long long usecs_to_ticks(unsigned long usecs)
  36{
  37        unsigned long long ticks = (unsigned long long)usecs * TIMER_FREQ;
  38        do_div(ticks, 1000 * 1000);
  39
  40        return ticks;
  41}
  42
  43static inline void read_timer(void)
  44{
  45        struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
  46        const unsigned long now = TIMER_MAX_VAL - readl(&timer_regs->timer3.value);
  47
  48        if (now >= timer.last_read)
  49                timer.ticks += now - timer.last_read;
  50        else
  51                /* an overflow occurred */
  52                timer.ticks += TIMER_MAX_VAL - timer.last_read + now;
  53
  54        timer.last_read = now;
  55}
  56
  57/*
  58 * Get the number of ticks (in CONFIG_SYS_HZ resolution)
  59 */
  60unsigned long long get_ticks(void)
  61{
  62        unsigned long long sys_ticks;
  63
  64        read_timer();
  65
  66        sys_ticks = timer.ticks * CONFIG_SYS_HZ;
  67        do_div(sys_ticks, TIMER_FREQ);
  68
  69        return sys_ticks;
  70}
  71
  72unsigned long get_timer(unsigned long base)
  73{
  74        return get_ticks() - base;
  75}
  76
  77void __udelay(unsigned long usec)
  78{
  79        unsigned long long target;
  80
  81        read_timer();
  82
  83        target = timer.ticks + usecs_to_ticks(usec);
  84
  85        while (timer.ticks < target)
  86                read_timer();
  87}
  88
  89int timer_init(void)
  90{
  91        struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
  92
  93        /* use timer 3 with 508KHz and free running, not enabled now */
  94        writel(TIMER_CLKSEL, &timer_regs->timer3.control);
  95
  96        /* set initial timer value */
  97        writel(TIMER_MAX_VAL, &timer_regs->timer3.load);
  98
  99        /* Enable the timer */
 100        writel(TIMER_ENABLE | TIMER_CLKSEL,
 101                &timer_regs->timer3.control);
 102
 103        /* Reset the timer */
 104        read_timer();
 105        timer.ticks = 0;
 106
 107        return 0;
 108}
 109
 110/*
 111 * This function is derived from PowerPC code (timebase clock frequency).
 112 * On ARM it returns the number of timer ticks per second.
 113 */
 114unsigned long get_tbclk(void)
 115{
 116        return CONFIG_SYS_HZ;
 117}
 118