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
  10 #include <asm/arm/cpu.h>
  11
  12 #include <kernel_base.h>
  13
  14 #include <proto/kernel.h>
  15
  16 AROS_LH2(spinlock_t *, KrnSpinLock,
  17         AROS_LHA(spinlock_t *, lock, A0),
  18         AROS_LHA(ULONG, mode, D0),
  19         struct KernelBase *, KernelBase, 43, Kernel)
  20 {
  21     AROS_LIBFUNC_INIT
  22
  23     unsigned long lock_value, result;
  24
  25     if (mode == SPINLOCK_MODE_WRITE)
  26     {
  27         asm volatile(
  28                 "1:     ldrex   %0, [%1]        \n\t"   // Load the lock value and gain exclusive lock to memory
  29                 "       teq     %0, #0          \n\t"   // is the value 0? It means the lock was free
  30                 "       wfene                   \n\t"   // Wait for Event if lock was not free
  31                 "       strexeq %0, %2, [%1]    \n\t"   // Store value to memory and check if it succeeded
  32                 "       teq     %0, #0          \n\t"   // Test if write succeeded
  33                 "       bne     1b              \n\t"   // Try again if locking failed
  34                 : "=&r"(lock_value)
  35                 : "r" (&lock->lock), "r"(0x80000000)
  36                 : "cc"
  37         );
  38     }
  39     else
  40     {
  41         asm volatile(
  42                 "1:     ldrex   %0, [%2]        \n\t"   // Load lock value and gain exclusive lock to memory
  43                 "       adds    %0, %0, #1      \n\t"   // Increase the lock value and update conditional bits
  44                 "       wfemi                   \n\t"   // Wait for event if lock value was negative
  45                 "       strexpl %1, %0, [%2]    \n\t"   // Store value to memory if positive and check result
  46                 "       rsbpls  %0, %1, #0      \n\t"   // Reverse substract and update conditionals: if strex write was
  47                                                         // successful, %0 contains 0. #0 - %0 clears N flag. If write failed
  48                                                         // %0 contains 1. #0 - %0 sets N flag (value 0xffffffff).
  49                 "       bmi     1b              \n\t"   // Try again if N flag is set (because of locok value or write failure
  50                 : "=&r"(lock_value), "=&r"(result)
  51                 : "r"(&lock->lock)
  52                 : "cc"
  53         );
  54     }
  55
  56     dmb();
  57     return lock;
  58
  59     AROS_LIBFUNC_EXIT
  60 }