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i8259.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Code to handle x86 style IRQs plus some generic interrupt stuff.
 *
 * Copyright (C) 1992 Linus Torvalds
 * Copyright (C) 1994 - 2000 Ralf Baechle
 */
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/sysdev.h>

#include <asm/i8259.h>
#include <asm/io.h>

/*
 * This is the 'legacy' 8259A Programmable Interrupt Controller,
 * present in the majority of PC/AT boxes.
 * plus some generic x86 specific things if generic specifics makes
 * any sense at all.
 * this file should become arch/i386/kernel/irq.c when the old irq.c
 * moves to arch independent land
 */

static int i8259A_auto_eoi = -1;
DEFINE_SPINLOCK(i8259A_lock);
static void disable_8259A_irq(unsigned int irq);
static void enable_8259A_irq(unsigned int irq);
static void mask_and_ack_8259A(unsigned int irq);
static void init_8259A(int auto_eoi);

static struct irq_chip i8259A_chip = {
      .name       = "XT-PIC",
      .mask       = disable_8259A_irq,
      .disable    = disable_8259A_irq,
      .unmask           = enable_8259A_irq,
      .mask_ack   = mask_and_ack_8259A,
#ifdef CONFIG_MIPS_MT_SMTC_IRQAFF
      .set_affinity     = plat_set_irq_affinity,
#endif /* CONFIG_MIPS_MT_SMTC_IRQAFF */
};

/*
 * 8259A PIC functions to handle ISA devices:
 */

/*
 * This contains the irq mask for both 8259A irq controllers,
 */
static unsigned int cached_irq_mask = 0xffff;

#define cached_master_mask    (cached_irq_mask)
#define cached_slave_mask     (cached_irq_mask >> 8)

static void disable_8259A_irq(unsigned int irq)
{
      unsigned int mask;
      unsigned long flags;

      irq -= I8259A_IRQ_BASE;
      mask = 1 << irq;
      spin_lock_irqsave(&i8259A_lock, flags);
      cached_irq_mask |= mask;
      if (irq & 8)
            outb(cached_slave_mask, PIC_SLAVE_IMR);
      else
            outb(cached_master_mask, PIC_MASTER_IMR);
      spin_unlock_irqrestore(&i8259A_lock, flags);
}

static void enable_8259A_irq(unsigned int irq)
{
      unsigned int mask;
      unsigned long flags;

      irq -= I8259A_IRQ_BASE;
      mask = ~(1 << irq);
      spin_lock_irqsave(&i8259A_lock, flags);
      cached_irq_mask &= mask;
      if (irq & 8)
            outb(cached_slave_mask, PIC_SLAVE_IMR);
      else
            outb(cached_master_mask, PIC_MASTER_IMR);
      spin_unlock_irqrestore(&i8259A_lock, flags);
}

int i8259A_irq_pending(unsigned int irq)
{
      unsigned int mask;
      unsigned long flags;
      int ret;

      irq -= I8259A_IRQ_BASE;
      mask = 1 << irq;
      spin_lock_irqsave(&i8259A_lock, flags);
      if (irq < 8)
            ret = inb(PIC_MASTER_CMD) & mask;
      else
            ret = inb(PIC_SLAVE_CMD) & (mask >> 8);
      spin_unlock_irqrestore(&i8259A_lock, flags);

      return ret;
}

void make_8259A_irq(unsigned int irq)
{
      disable_irq_nosync(irq);
      set_irq_chip_and_handler(irq, &i8259A_chip, handle_level_irq);
      enable_irq(irq);
}

/*
 * This function assumes to be called rarely. Switching between
 * 8259A registers is slow.
 * This has to be protected by the irq controller spinlock
 * before being called.
 */
static inline int i8259A_irq_real(unsigned int irq)
{
      int value;
      int irqmask = 1 << irq;

      if (irq < 8) {
            outb(0x0B, PIC_MASTER_CMD);   /* ISR register */
            value = inb(PIC_MASTER_CMD) & irqmask;
            outb(0x0A, PIC_MASTER_CMD);   /* back to the IRR register */
            return value;
      }
      outb(0x0B, PIC_SLAVE_CMD);    /* ISR register */
      value = inb(PIC_SLAVE_CMD) & (irqmask >> 8);
      outb(0x0A, PIC_SLAVE_CMD);    /* back to the IRR register */
      return value;
}

/*
 * Careful! The 8259A is a fragile beast, it pretty
 * much _has_ to be done exactly like this (mask it
 * first, _then_ send the EOI, and the order of EOI
 * to the two 8259s is important!
 */
static void mask_and_ack_8259A(unsigned int irq)
{
      unsigned int irqmask;
      unsigned long flags;

      irq -= I8259A_IRQ_BASE;
      irqmask = 1 << irq;
      spin_lock_irqsave(&i8259A_lock, flags);
      /*
       * Lightweight spurious IRQ detection. We do not want
       * to overdo spurious IRQ handling - it's usually a sign
       * of hardware problems, so we only do the checks we can
       * do without slowing down good hardware unnecessarily.
       *
       * Note that IRQ7 and IRQ15 (the two spurious IRQs
       * usually resulting from the 8259A-1|2 PICs) occur
       * even if the IRQ is masked in the 8259A. Thus we
       * can check spurious 8259A IRQs without doing the
       * quite slow i8259A_irq_real() call for every IRQ.
       * This does not cover 100% of spurious interrupts,
       * but should be enough to warn the user that there
       * is something bad going on ...
       */
      if (cached_irq_mask & irqmask)
            goto spurious_8259A_irq;
      cached_irq_mask |= irqmask;

handle_real_irq:
      if (irq & 8) {
            inb(PIC_SLAVE_IMR);     /* DUMMY - (do we need this?) */
            outb(cached_slave_mask, PIC_SLAVE_IMR);
            outb(0x60+(irq&7), PIC_SLAVE_CMD);/* 'Specific EOI' to slave */
            outb(0x60+PIC_CASCADE_IR, PIC_MASTER_CMD); /* 'Specific EOI' to master-IRQ2 */
      } else {
            inb(PIC_MASTER_IMR);    /* DUMMY - (do we need this?) */
            outb(cached_master_mask, PIC_MASTER_IMR);
            outb(0x60+irq, PIC_MASTER_CMD);     /* 'Specific EOI to master */
      }
      smtc_im_ack_irq(irq);
      spin_unlock_irqrestore(&i8259A_lock, flags);
      return;

spurious_8259A_irq:
      /*
       * this is the slow path - should happen rarely.
       */
      if (i8259A_irq_real(irq))
            /*
             * oops, the IRQ _is_ in service according to the
             * 8259A - not spurious, go handle it.
             */
            goto handle_real_irq;

      {
            static int spurious_irq_mask;
            /*
             * At this point we can be sure the IRQ is spurious,
             * lets ACK and report it. [once per IRQ]
             */
            if (!(spurious_irq_mask & irqmask)) {
                  printk(KERN_DEBUG "spurious 8259A interrupt: IRQ%d.\n", irq);
                  spurious_irq_mask |= irqmask;
            }
            atomic_inc(&irq_err_count);
            /*
             * Theoretically we do not have to handle this IRQ,
             * but in Linux this does not cause problems and is
             * simpler for us.
             */
            goto handle_real_irq;
      }
}

static int i8259A_resume(struct sys_device *dev)
{
      if (i8259A_auto_eoi >= 0)
            init_8259A(i8259A_auto_eoi);
      return 0;
}

static int i8259A_shutdown(struct sys_device *dev)
{
      /* Put the i8259A into a quiescent state that
       * the kernel initialization code can get it
       * out of.
       */
      if (i8259A_auto_eoi >= 0) {
            outb(0xff, PIC_MASTER_IMR);   /* mask all of 8259A-1 */
            outb(0xff, PIC_SLAVE_IMR);    /* mask all of 8259A-1 */
      }
      return 0;
}

static struct sysdev_class i8259_sysdev_class = {
      .name = "i8259",
      .resume = i8259A_resume,
      .shutdown = i8259A_shutdown,
};

static struct sys_device device_i8259A = {
      .id   = 0,
      .cls  = &i8259_sysdev_class,
};

static int __init i8259A_init_sysfs(void)
{
      int error = sysdev_class_register(&i8259_sysdev_class);
      if (!error)
            error = sysdev_register(&device_i8259A);
      return error;
}

device_initcall(i8259A_init_sysfs);

static void init_8259A(int auto_eoi)
{
      unsigned long flags;

      i8259A_auto_eoi = auto_eoi;

      spin_lock_irqsave(&i8259A_lock, flags);

      outb(0xff, PIC_MASTER_IMR);   /* mask all of 8259A-1 */
      outb(0xff, PIC_SLAVE_IMR);    /* mask all of 8259A-2 */

      /*
       * outb_p - this has to work on a wide range of PC hardware.
       */
      outb_p(0x11, PIC_MASTER_CMD); /* ICW1: select 8259A-1 init */
      outb_p(I8259A_IRQ_BASE + 0, PIC_MASTER_IMR);    /* ICW2: 8259A-1 IR0 mapped to I8259A_IRQ_BASE + 0x00 */
      outb_p(1U << PIC_CASCADE_IR, PIC_MASTER_IMR);   /* 8259A-1 (the master) has a slave on IR2 */
      if (auto_eoi)     /* master does Auto EOI */
            outb_p(MASTER_ICW4_DEFAULT | PIC_ICW4_AEOI, PIC_MASTER_IMR);
      else        /* master expects normal EOI */
            outb_p(MASTER_ICW4_DEFAULT, PIC_MASTER_IMR);

      outb_p(0x11, PIC_SLAVE_CMD);  /* ICW1: select 8259A-2 init */
      outb_p(I8259A_IRQ_BASE + 8, PIC_SLAVE_IMR);     /* ICW2: 8259A-2 IR0 mapped to I8259A_IRQ_BASE + 0x08 */
      outb_p(PIC_CASCADE_IR, PIC_SLAVE_IMR);    /* 8259A-2 is a slave on master's IR2 */
      outb_p(SLAVE_ICW4_DEFAULT, PIC_SLAVE_IMR); /* (slave's support for AEOI in flat mode is to be investigated) */
      if (auto_eoi)
            /*
             * In AEOI mode we just have to mask the interrupt
             * when acking.
             */
            i8259A_chip.mask_ack = disable_8259A_irq;
      else
            i8259A_chip.mask_ack = mask_and_ack_8259A;

      udelay(100);            /* wait for 8259A to initialize */

      outb(cached_master_mask, PIC_MASTER_IMR); /* restore master IRQ mask */
      outb(cached_slave_mask, PIC_SLAVE_IMR);     /* restore slave IRQ mask */

      spin_unlock_irqrestore(&i8259A_lock, flags);
}

/*
 * IRQ2 is cascade interrupt to second interrupt controller
 */
static struct irqaction irq2 = {
      .handler = no_action,
      .name = "cascade",
};

static struct resource pic1_io_resource = {
      .name = "pic1",
      .start = PIC_MASTER_CMD,
      .end = PIC_MASTER_IMR,
      .flags = IORESOURCE_BUSY
};

static struct resource pic2_io_resource = {
      .name = "pic2",
      .start = PIC_SLAVE_CMD,
      .end = PIC_SLAVE_IMR,
      .flags = IORESOURCE_BUSY
};

/*
 * On systems with i8259-style interrupt controllers we assume for
 * driver compatibility reasons interrupts 0 - 15 to be the i8259
 * interrupts even if the hardware uses a different interrupt numbering.
 */
void __init init_i8259_irqs(void)
{
      int i;

      insert_resource(&ioport_resource, &pic1_io_resource);
      insert_resource(&ioport_resource, &pic2_io_resource);

      init_8259A(0);

      for (i = I8259A_IRQ_BASE; i < I8259A_IRQ_BASE + 16; i++) {
            set_irq_chip_and_handler(i, &i8259A_chip, handle_level_irq);
            set_irq_probe(i);
      }

      setup_irq(I8259A_IRQ_BASE + PIC_CASCADE_IR, &irq2);
}

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