arch/arm-native/kernel/spinlock.c

   1 /*
   2     Copyright © 2015, The AROS Development Team. All rights reserved.
   3     $Id$
   4 */
   5
   6 #include <aros/types/spinlock_s.h>
   7 #include <aros/kernel.h>
   8 #include <aros/libcall.h>
   9 #include <utility/hooks.h>
  10
  11 #include <asm/arm/cpu.h>
  12
  13 #include <kernel_base.h>
  14
  15 #include <proto/kernel.h>
  16
  17 AROS_LH3(spinlock_t *, KrnSpinLock,
  18         AROS_LHA(spinlock_t *, lock, A1),
  19         AROS_LHA(struct Hook *, failhook, A0),
  20         AROS_LHA(ULONG, mode, D0),
  21         struct KernelBase *, KernelBase, 43, Kernel)
  22 {
  23     AROS_LIBFUNC_INIT
  24
  25     unsigned long lock_value, result;
  26
  27     if (mode == SPINLOCK_MODE_WRITE)
  28     {
  29         asm volatile(
  30                 "1:     ldrex   %0, [%1]        \n\t"   // Load the lock value, gaining exclusive access
  31                 "       teq     %0, #0          \n\t"   // Is the lock free?
  32                 "       wfene                   \n\t"   // Wait for Event if allready obtained
  33                 "       strexeq %0, %2, [%1]    \n\t"   // Try to exclusively write the lock value to memory
  34                 "       teq     %0, #0          \n\t"   // Did it succeeded?
  35                 "       bne     1b              \n\t"   // If we failed, try to obtain the lock again
  36                 : "=&r"(lock_value)
  37                 : "r" (&lock->lock), "r"(0x80000000)
  38                 : "cc"
  39         );
  40     }
  41     else
  42     {
  43         asm volatile(
  44                 "1:     ldrex   %0, [%2]        \n\t"   // Load the lock value, gaining exclusive access
  45                 "       adds    %0, %0, #1      \n\t"   // Increase the lock value and update conditional bits
  46                 "       wfemi                   \n\t"   // Wait for event if lock value is negative
  47                 "       strexpl %1, %0, [%2]    \n\t"   // Try to exclusively write the lock value to memory if positive
  48                 "       rsbpls  %0, %1, #0      \n\t"   // Reverse substract and update conditionals:
  49                                                         // - if strex write was successful, %0 contains 0. #0 - %0 clears N flag.
  50                                                         // - If write failed %0 contains 1. #0 - %0 sets N flag (value 0xffffffff).
  51                 "       bmi     1b              \n\t"   // Try again if N flag is set (because of lock value, or write failure)
  52                 : "=&r"(lock_value), "=&r"(result)
  53                 : "r"(&lock->lock)
  54                 : "cc"
  55         );
  56     }
  57
  58     dmb();
  59     return lock;
  60
  61     AROS_LIBFUNC_EXIT
  62 }