arch/mips/include/asm/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 #include <irq.h>
  22
  23 /* i8259A PIC registers */
  24 #define PIC_MASTER_CMD          0x20
  25 #define PIC_MASTER_IMR          0x21
  26 #define PIC_MASTER_ISR          PIC_MASTER_CMD
  27 #define PIC_MASTER_POLL         PIC_MASTER_ISR
  28 #define PIC_MASTER_OCW3         PIC_MASTER_ISR
  29 #define PIC_SLAVE_CMD           0xa0
  30 #define PIC_SLAVE_IMR           0xa1
  31
  32 /* i8259A PIC related value */
  33 #define PIC_CASCADE_IR          2
  34 #define MASTER_ICW4_DEFAULT     0x01
  35 #define SLAVE_ICW4_DEFAULT      0x01
  36 #define PIC_ICW4_AEOI           2
  37
  38 extern raw_spinlock_t i8259A_lock;
  39
  40 extern int i8259A_irq_pending(unsigned int irq);
  41 extern void make_8259A_irq(unsigned int irq);
  42
  43 extern void init_i8259_irqs(void);
  44
  45 /*
  46  * Do the traditional i8259 interrupt polling thing.  This is for the few
  47  * cases where no better interrupt acknowledge method is available and we
  48  * absolutely must touch the i8259.
  49  */
  50 static inline int i8259_irq(void)
  51 {
  52         int irq;
  53
  54         raw_spin_lock(&i8259A_lock);
  55
  56         /* Perform an interrupt acknowledge cycle on controller 1. */
  57         outb(0x0C, PIC_MASTER_CMD);             /* prepare for poll */
  58         irq = inb(PIC_MASTER_CMD) & 7;
  59         if (irq == PIC_CASCADE_IR) {
  60                 /*
  61                  * Interrupt is cascaded so perform interrupt
  62                  * acknowledge on controller 2.
  63                  */
  64                 outb(0x0C, PIC_SLAVE_CMD);              /* prepare for poll */
  65                 irq = (inb(PIC_SLAVE_CMD) & 7) + 8;
  66         }
  67
  68         if (unlikely(irq == 7)) {
  69                 /*
  70                  * This may be a spurious interrupt.
  71                  *
  72                  * Read the interrupt status register (ISR). If the most
  73                  * significant bit is not set then there is no valid
  74                  * interrupt.
  75                  */
  76                 outb(0x0B, PIC_MASTER_ISR);             /* ISR register */
  77                 if(~inb(PIC_MASTER_ISR) & 0x80)
  78                         irq = -1;
  79         }
  80
  81         raw_spin_unlock(&i8259A_lock);
  82
  83         return likely(irq >= 0) ? irq + I8259A_IRQ_BASE : irq;
  84 }
  85
  86 #endif /* _ASM_I8259_H */