arch/metag/kernel/kick.c

   1 /*
   2  *  Copyright (C) 2009 Imagination Technologies
   3  *
   4  * This file is subject to the terms and conditions of the GNU General Public
   5  * License.  See the file COPYING in the main directory of this archive
   6  * for more details.
   7  *
   8  * The Meta KICK interrupt mechanism is generally a useful feature, so
   9  * we provide an interface for registering multiple interrupt
  10  * handlers. All the registered interrupt handlers are "chained". When
  11  * a KICK interrupt is received the first function in the list is
  12  * called. If that interrupt handler cannot handle the KICK the next
  13  * one is called, then the next until someone handles it (or we run
  14  * out of functions). As soon as one function handles the interrupt no
  15  * other handlers are called.
  16  *
  17  * The only downside of chaining interrupt handlers is that each
  18  * handler must be able to detect whether the KICK was intended for it
  19  * or not.  For example, when the IPI handler runs and it sees that
  20  * there are no IPI messages it must not signal that the KICK was
  21  * handled, thereby giving the other handlers a chance to run.
  22  *
  23  * The reason that we provide our own interface for calling KICK
  24  * handlers instead of using the generic kernel infrastructure is that
  25  * the KICK handlers require access to a CPU's pTBI structure. So we
  26  * pass it as an argument.
  27  */
  28 #include <linux/export.h>
  29 #include <linux/hardirq.h>
  30 #include <linux/irq.h>
  31 #include <linux/kernel.h>
  32 #include <linux/mm.h>
  33 #include <linux/types.h>
  34
  35 #include <asm/traps.h>
  36
  37 /*
  38  * All accesses/manipulations of kick_handlers_list should be
  39  * performed while holding kick_handlers_lock.
  40  */
  41 static DEFINE_SPINLOCK(kick_handlers_lock);
  42 static LIST_HEAD(kick_handlers_list);
  43
  44 void kick_register_func(struct kick_irq_handler *kh)
  45 {
  46         unsigned long flags;
  47
  48         spin_lock_irqsave(&kick_handlers_lock, flags);
  49
  50         list_add_tail(&kh->list, &kick_handlers_list);
  51
  52         spin_unlock_irqrestore(&kick_handlers_lock, flags);
  53 }
  54 EXPORT_SYMBOL(kick_register_func);
  55
  56 void kick_unregister_func(struct kick_irq_handler *kh)
  57 {
  58         unsigned long flags;
  59
  60         spin_lock_irqsave(&kick_handlers_lock, flags);
  61
  62         list_del(&kh->list);
  63
  64         spin_unlock_irqrestore(&kick_handlers_lock, flags);
  65 }
  66 EXPORT_SYMBOL(kick_unregister_func);
  67
  68 TBIRES
  69 kick_handler(TBIRES State, int SigNum, int Triggers, int Inst, PTBI pTBI)
  70 {
  71         struct pt_regs *old_regs;
  72         struct kick_irq_handler *kh;
  73         struct list_head *lh;
  74         int handled = 0;
  75         TBIRES ret;
  76
  77         head_end(State, ~INTS_OFF_MASK);
  78
  79         /* If we interrupted user code handle any critical sections. */
  80         if (State.Sig.SaveMask & TBICTX_PRIV_BIT)
  81                 restart_critical_section(State);
  82
  83         trace_hardirqs_off();
  84
  85         old_regs = set_irq_regs((struct pt_regs *)State.Sig.pCtx);
  86         irq_enter();
  87
  88         /*
  89          * There is no need to disable interrupts here because we
  90          * can't nest KICK interrupts in a KICK interrupt handler.
  91          */
  92         spin_lock(&kick_handlers_lock);
  93
  94         list_for_each(lh, &kick_handlers_list) {
  95                 kh = list_entry(lh, struct kick_irq_handler, list);
  96
  97                 ret = kh->func(State, SigNum, Triggers, Inst, pTBI, &handled);
  98                 if (handled)
  99                         break;
 100         }
 101
 102         spin_unlock(&kick_handlers_lock);
 103
 104         WARN_ON(!handled);
 105
 106         irq_exit();
 107         set_irq_regs(old_regs);
 108
 109         return tail_end(ret);
 110 }