target/linux/ubicom32/files/arch/ubicom32/include/asm/system.h

   1 /*
   2  * arch/ubicom32/include/asm/system.h
   3  *   Low level switching definitions.
   4  *
   5  * (C) Copyright 2009, Ubicom, Inc.
   6  *
   7  * This file is part of the Ubicom32 Linux Kernel Port.
   8  *
   9  * The Ubicom32 Linux Kernel Port is free software: you can redistribute
  10  * it and/or modify it under the terms of the GNU General Public License
  11  * as published by the Free Software Foundation, either version 2 of the
  12  * License, or (at your option) any later version.
  13  *
  14  * The Ubicom32 Linux Kernel Port is distributed in the hope that it
  15  * will be useful, but WITHOUT ANY WARRANTY; without even the implied
  16  * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  17  * the GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with the Ubicom32 Linux Kernel Port.  If not,
  21  * see <http://www.gnu.org/licenses/>.
  22  *
  23  * Ubicom32 implementation derived from (with many thanks):
  24  *   arch/m68knommu
  25  *   arch/blackfin
  26  *   arch/parisc
  27  */
  28 #ifndef _ASM_UBICOM32_SYSTEM_H
  29 #define _ASM_UBICOM32_SYSTEM_H
  30
  31 #include <linux/irqflags.h>
  32 #include <linux/linkage.h>
  33 #include <asm/segment.h>
  34 #include <asm/entry.h>
  35 #include <asm/ldsr.h>
  36 #include <asm/irq.h>
  37 #include <asm/percpu.h>
  38 #include <asm/ubicom32-common.h>
  39 #include <asm/processor.h>
  40
  41 /*
  42  * switch_to(n) should switch tasks to task ptr, first checking that
  43  * ptr isn't the current task, in which case it does nothing.
  44  */
  45 asmlinkage void resume(void);
  46 extern void *__switch_to(struct task_struct *prev,
  47                 struct thread_struct *prev_switch,
  48                 struct thread_struct *next_switch);
  49
  50 /*
  51  * We will need a per linux thread sw_ksp for the switch_to macro to
  52  * track the kernel stack pointer for the current thread on that linux thread.
  53  */
  54 #define switch_to(prev,next,last)                                       \
  55 ({                                                                      \
  56         void *_last;                                                    \
  57         _last = (void *)                                                \
  58                 __switch_to(prev, &prev->thread, &next->thread);        \
  59         (last) = _last;                                                 \
  60 })
  61
  62 /*
  63  * Force strict CPU ordering.
  64  * Not really required on ubicom32...
  65  */
  66 #define nop()  asm volatile ("nop"::)
  67 #define mb()   asm volatile (""   : : :"memory")
  68 #define rmb()  asm volatile (""   : : :"memory")
  69 #define wmb()  asm volatile (""   : : :"memory")
  70 #define set_mb(var, value)      ({ (var) = (value); wmb(); })
  71
  72 #ifdef CONFIG_SMP
  73 #define smp_mb()        mb()
  74 #define smp_rmb()       rmb()
  75 #define smp_wmb()       wmb()
  76 #define smp_read_barrier_depends()      read_barrier_depends()
  77 #else
  78 #define smp_mb()        mb()
  79 #define smp_rmb()       rmb()
  80 #define smp_wmb()       wmb()
  81 #define smp_read_barrier_depends()      do { } while(0)
  82 #endif
  83
  84 #define read_barrier_depends()  ((void)0)
  85
  86 /*
  87  * The following defines change how the scheduler calls the switch_to()
  88  * macro.
  89  *
  90  * 1) The first causes the runqueue to be unlocked on entry to
  91  * switch_to().  Since our ctx code does not play with the runqueue
  92  * we do not need it unlocked.
  93  *
  94  * 2) The later turns interrupts on during a ctxsw to reduce the latency of
  95  * interrupts during ctx.  At this point in the port, we believe that this
  96  * latency is not a problem since we have very little code to perform a ctxsw.
  97  */
  98 // #define __ARCH_WANT_UNLOCKED_CTXSW
  99 // #define __ARCH_WANT_INTERRUPTS_ON_CTXSW
 100
 101 #endif /* _ASM_UBICOM32_SYSTEM_H */