arch/xtensa/lib/time.c

   1 /*
   2  * (C) Copyright 2008 - 2013 Tensilica Inc.
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  */
   6
   7 #include <common.h>
   8 #include <asm/global_data.h>
   9 #include <linux/stringify.h>
  10
  11 DECLARE_GLOBAL_DATA_PTR;
  12
  13 #if XCHAL_HAVE_CCOUNT
  14 static ulong get_ccount(void)
  15 {
  16         ulong ccount;
  17         asm volatile ("rsr %0,"__stringify(CCOUNT) : "=a" (ccount));
  18         return ccount;
  19 }
  20 #else
  21 static ulong fake_ccount;
  22 #define get_ccount() fake_ccount
  23 #endif
  24
  25 static void delay_cycles(unsigned cycles)
  26 {
  27 #if XCHAL_HAVE_CCOUNT
  28         unsigned expiry = get_ccount() + cycles;
  29         while ((signed)(expiry - get_ccount()) > 0)
  30                 ;
  31 #else
  32 #warning "Without Xtensa timer option, timing will not be accurate."
  33
  34         /*
  35          * Approximate the cycle count by a loop iteration count.
  36          * This is highly dependent on config and optimization.
  37          */
  38
  39         volatile unsigned i;
  40         for (i = cycles >> 4U; i > 0; --i)
  41                 ;
  42         fake_ccount += cycles;
  43 #endif
  44 }
  45
  46 /*
  47  * Delay (busy-wait) for a number of microseconds.
  48  */
  49
  50 void __udelay(unsigned long usec)
  51 {
  52         ulong lo, hi, i;
  53         ulong mhz = CONFIG_SYS_CLK_FREQ / 1000000;
  54
  55         /* Scale to support full 32-bit usec range */
  56
  57         lo = usec & ((1<<22)-1);
  58         hi = usec >> 22UL;
  59         for (i = 0; i < hi; ++i)
  60                 delay_cycles(mhz << 22);
  61         delay_cycles(mhz * lo);
  62 }
  63
  64
  65 /*
  66  * Return the elapsed time (ticks) since 'base'.
  67  */
  68
  69 ulong get_timer(ulong base)
  70 {
  71         /* Don't tie up a timer; use cycle counter if available (or fake it) */
  72
  73 #if XCHAL_HAVE_CCOUNT
  74         register ulong ccount;
  75         __asm__ volatile ("rsr %0, CCOUNT" : "=a"(ccount));
  76         return ccount / (CONFIG_SYS_CLK_FREQ / CONFIG_SYS_HZ) - base;
  77 #else
  78         /*
  79          * Add at least the overhead of this call (in cycles).
  80          * Avoids hanging in case caller doesn't use udelay().
  81          * Note that functions that don't call udelay() (such as
  82          * the "sleep" command) will not get a significant delay
  83          * because there is no time reference.
  84          */
  85
  86         fake_ccount += 20;
  87         return fake_ccount / (CONFIG_SYS_CLK_FREQ / CONFIG_SYS_HZ) - base;
  88 #endif
  89 }
  90
  91
  92 /*
  93  * This function is derived from ARM/PowerPC code (read timebase as long long).
  94  * On Xtensa it just returns the timer value.
  95  */
  96 unsigned long long get_ticks(void)
  97 {
  98         return get_timer(0);
  99 }
 100
 101 /*
 102  * This function is derived from ARM/PowerPC code (timebase clock frequency).
 103  * On Xtensa it returns the number of timer ticks per second.
 104  */
 105 ulong get_tbclk(void)
 106 {
 107         ulong tbclk;
 108
 109         tbclk = CONFIG_SYS_HZ;
 110         return tbclk;
 111 }
 112
 113 #if XCHAL_HAVE_CCOUNT
 114 unsigned long timer_get_us(void)
 115 {
 116         unsigned long ccount;
 117
 118         __asm__ volatile ("rsr %0, CCOUNT" : "=a"(ccount));
 119         return ccount / (CONFIG_SYS_CLK_FREQ / 1000000);
 120 }
 121 #endif