arch/xtensa/lib/time.c

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