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 <linux/types.h>
  16 #include <asm/arch/ep93xx.h>
  17 #include <asm/io.h>
  18 #include <div64.h>
  19
  20 #define TIMER_CLKSEL    (1 << 3)
  21 #define TIMER_ENABLE    (1 << 7)
  22
  23 #define TIMER_FREQ                      508469          /* ticks / second */
  24 #define TIMER_MAX_VAL                   0xFFFFFFFF
  25
  26 static struct ep93xx_timer
  27 {
  28         unsigned long long ticks;
  29         unsigned long last_read;
  30 } timer;
  31
  32 static inline unsigned long long usecs_to_ticks(unsigned long usecs)
  33 {
  34         unsigned long long ticks = (unsigned long long)usecs * TIMER_FREQ;
  35         do_div(ticks, 1000 * 1000);
  36
  37         return ticks;
  38 }
  39
  40 static inline void read_timer(void)
  41 {
  42         struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
  43         const unsigned long now = TIMER_MAX_VAL - readl(&timer_regs->timer3.value);
  44
  45         if (now >= timer.last_read)
  46                 timer.ticks += now - timer.last_read;
  47         else
  48                 /* an overflow occurred */
  49                 timer.ticks += TIMER_MAX_VAL - timer.last_read + now;
  50
  51         timer.last_read = now;
  52 }
  53
  54 /*
  55  * Get the number of ticks (in CONFIG_SYS_HZ resolution)
  56  */
  57 unsigned long long get_ticks(void)
  58 {
  59         unsigned long long sys_ticks;
  60
  61         read_timer();
  62
  63         sys_ticks = timer.ticks * CONFIG_SYS_HZ;
  64         do_div(sys_ticks, TIMER_FREQ);
  65
  66         return sys_ticks;
  67 }
  68
  69 unsigned long get_timer_masked(void)
  70 {
  71         return get_ticks();
  72 }
  73
  74 unsigned long get_timer(unsigned long base)
  75 {
  76         return get_timer_masked() - base;
  77 }
  78
  79 void __udelay(unsigned long usec)
  80 {
  81         unsigned long long target;
  82
  83         read_timer();
  84
  85         target = timer.ticks + usecs_to_ticks(usec);
  86
  87         while (timer.ticks < target)
  88                 read_timer();
  89 }
  90
  91 int timer_init(void)
  92 {
  93         struct timer_regs *timer_regs = (struct timer_regs *)TIMER_BASE;
  94
  95         /* use timer 3 with 508KHz and free running, not enabled now */
  96         writel(TIMER_CLKSEL, &timer_regs->timer3.control);
  97
  98         /* set initial timer value */
  99         writel(TIMER_MAX_VAL, &timer_regs->timer3.load);
 100
 101         /* Enable the timer */
 102         writel(TIMER_ENABLE | TIMER_CLKSEL,
 103                 &timer_regs->timer3.control);
 104
 105         /* Reset the timer */
 106         read_timer();
 107         timer.ticks = 0;
 108
 109         return 0;
 110 }
 111
 112 /*
 113  * This function is derived from PowerPC code (timebase clock frequency).
 114  * On ARM it returns the number of timer ticks per second.
 115  */
 116 unsigned long get_tbclk(void)
 117 {
 118         return CONFIG_SYS_HZ;
 119 }