alt_dcache_flush.c

nios中自定义指令集实现三角函数的软件部分。

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#include "nios2.h"
#include "system.h"

#include "alt_types.h"
#include "sys/alt_cache.h" 

/*
 * Nios II version 1.2 and newer supports the "flush by address" instruction, in
 * addition to the "flush by line" instruction provided by older versions of
 * the core. This newer instruction is used by preference when it is 
 * available.
 */

#ifdef NIOS2_FLUSHDA_SUPPORTED
#define ALT_FLUSH_DATA(i) __asm__ volatile ("flushda (%0)" :: "r" (i));
#else
#define ALT_FLUSH_DATA(i) __asm__ volatile ("flushd (%0)" :: "r" (i));
#endif /* NIOS2_FLUSHDA_SUPPORTED */

/*
 * alt_dcache_flush() is called to flush the data cache for a memory
 * region of length "len" bytes, starting at address "start".
 */

void alt_dcache_flush (void* start, alt_u32 len)
{
#if NIOS2_DCACHE_SIZE > 0

  char* i;
  char* end; 

  /*
   * This is the most we would ever need to flush.
   *
   * SPR 196942, 2006.01.13: The cache flush loop below will use the
   * 'flushda' instruction if its available; in that case each line
   * must be flushed individually, and thus 'len' cannot be trimmed.
   */
  #ifndef NIOS2_FLUSHDA_SUPPORTED
  if (len > NIOS2_DCACHE_SIZE)
  {
    len = NIOS2_DCACHE_SIZE;
  }
  #endif

  end = ((char*) start) + len; 

  for (i = start; i < end; i+= NIOS2_DCACHE_LINE_SIZE)
  { 
    ALT_FLUSH_DATA(i); 
  }

  /* 
   * For an unaligned flush request, we've got one more line left.
   * Note that this is dependent on NIOS2_DCACHE_LINE_SIZE to be a 
   * multiple of 2 (which it always is).
   */

  if (((alt_u32) start) & (NIOS2_DCACHE_LINE_SIZE - 1))
  {
    ALT_FLUSH_DATA(i);
  }

#endif /* NIOS2_DCACHE_SIZE > 0 */
}