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sead_int.c

/*
 * Carsten Langgaard, carstenl@mips.com
 * Copyright (C) 2002 MIPS Technologies, Inc.  All rights reserved.
 * Copyright (C) 2003 Ralf Baechle (ralf@linux-mips.org)
 * Copyright (C) 2004  Maciej W. Rozycki
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * Routines for generic manipulation of the interrupts found on the MIPS
 * Sead board.
 */
#include <linux/init.h>
#include <linux/interrupt.h>

#include <asm/irq_cpu.h>
#include <asm/mipsregs.h>
#include <asm/system.h>

#include <asm/mips-boards/seadint.h>

static inline int clz(unsigned long x)
{
      __asm__(
      "     .set  push                          \n"
      "     .set  mips32                              \n"
      "     clz   %0, %1                              \n"
      "     .set  pop                           \n"
      : "=r" (x)
      : "r" (x));

      return x;
}

/*
 * Version of ffs that only looks at bits 12..15.
 */
static inline unsigned int irq_ffs(unsigned int pending)
{
#if defined(CONFIG_CPU_MIPS32) || defined(CONFIG_CPU_MIPS64)
      return -clz(pending) + 31 - CAUSEB_IP;
#else
      unsigned int a0 = 7;
      unsigned int t0;

      t0 = s0 & 0xf000;
      t0 = t0 < 1;
      t0 = t0 << 2;
      a0 = a0 - t0;
      s0 = s0 << t0;

      t0 = s0 & 0xc000;
      t0 = t0 < 1;
      t0 = t0 << 1;
      a0 = a0 - t0;
      s0 = s0 << t0;

      t0 = s0 & 0x8000;
      t0 = t0 < 1;
      //t0 = t0 << 2;
      a0 = a0 - t0;
      //s0 = s0 << t0;

      return a0;
#endif
}

/*
 * IRQs on the SEAD board look basically are combined together on hardware
 * interrupt 0 (MIPS IRQ 2)) like:
 *
 *    MIPS IRQ    Source
 *      --------        ------
 *             0  Software (ignored)
 *             1        Software (ignored)
 *             2        UART0 (hw0)
 *             3        UART1 (hw1)
 *             4        Hardware (ignored)
 *             5        Hardware (ignored)
 *             6        Hardware (ignored)
 *             7        R4k timer (what we use)
 *
 * We handle the IRQ according to _our_ priority which is:
 *
 * Highest ----     R4k Timer
 * Lowest  ----     Combined hardware interrupt
 *
 * then we just return, if multiple IRQs are pending then we will just take
 * another exception, big deal.
 */
asmlinkage void plat_irq_dispatch(void)
{
      unsigned int pending = read_c0_cause() & read_c0_status() & ST0_IM;
      int irq;

      irq = irq_ffs(pending);

      if (irq >= 0)
            do_IRQ(MIPS_CPU_IRQ_BASE + irq);
      else
            spurious_interrupt();
}

void __init arch_init_irq(void)
{
      mips_cpu_irq_init();
}

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