[U-Boot-Users] about embedded assembly

[sun]

hello,all
  The following program is from MARVELL U-Boot
   
   
  if(mvCtrlModelGet() == MV_5281_DEV_ID) /* Orion 2 */
 {
    __asm__ __volatile__("mrc    p15, 0, %0, c14, c0, 0" : "=r" (temp):: "memory");
  if (temp & 0x10000000)
  {
   printf("CPU: Write allocate enabled\n");
  }
  else
  {
   printf("CPU: Write allocate Disabled\n");
  }
 }
   
   
  I don't understand what's the following sentense mean,please detailed explain it,thanks
   
  __asm__ __volatile__("mrc    p15, 0, %0, c14, c0, 0" : "=r" (temp):: "memory");

       
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