include/asm-mips/i8259.h

   1 /*
   2  *      include/asm-mips/i8259.h
   3  *
   4  *      i8259A interrupt definitions.
   5  *
   6  *      Copyright (C) 2003  Maciej W. Rozycki
   7  *      Copyright (C) 2003  Ralf Baechle <ralf@linux-mips.org>
   8  *
   9  *      This program is free software; you can redistribute it and/or
  10  *      modify it under the terms of the GNU General Public License
  11  *      as published by the Free Software Foundation; either version
  12  *      2 of the License, or (at your option) any later version.
  13  */
  14 #ifndef _ASM_I8259_H
  15 #define _ASM_I8259_H
  16
  17 #include <linux/compiler.h>
  18 #include <linux/spinlock.h>
  19
  20 #include <asm/io.h>
  21
  22 extern spinlock_t i8259A_lock;
  23
  24 extern void init_i8259_irqs(void);
  25
  26 /*
  27  * Do the traditional i8259 interrupt polling thing.  This is for the few
  28  * cases where no better interrupt acknowledge method is available and we
  29  * absolutely must touch the i8259.
  30  */
  31 static inline int i8259_irq(void)
  32 {
  33         int irq;
  34
  35         spin_lock(&i8259A_lock);
  36
  37         /* Perform an interrupt acknowledge cycle on controller 1. */
  38         outb(0x0C, 0x20);               /* prepare for poll */
  39         irq = inb(0x20) & 7;
  40         if (irq == 2) {
  41                 /*
  42                  * Interrupt is cascaded so perform interrupt
  43                  * acknowledge on controller 2.
  44                  */
  45                 outb(0x0C, 0xA0);               /* prepare for poll */
  46                 irq = (inb(0xA0) & 7) + 8;
  47         }
  48
  49         if (unlikely(irq == 7)) {
  50                 /*
  51                  * This may be a spurious interrupt.
  52                  *
  53                  * Read the interrupt status register (ISR). If the most
  54                  * significant bit is not set then there is no valid
  55                  * interrupt.
  56                  */
  57                 outb(0x0B, 0x20);               /* ISR register */
  58                 if(~inb(0x20) & 0x80)
  59                         irq = -1;
  60         }
  61
  62         spin_unlock(&i8259A_lock);
  63
  64         return irq;
  65 }
  66
  67 #endif /* _ASM_I8259_H */