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diff --git a/arch/mips/mips-boards/sim/sim_IRQ.c b/arch/mips/mips-boards/sim/sim_IRQ.c
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+/*
+ * Carsten Langgaard, carstenl@mips.com
+ * Copyright (C) 1999, 2000 MIPS Technologies, Inc. All rights reserved.
+ *
+ * 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.
+ *
+ * Interrupt exception dispatch code.
+ */
+#include <linux/config.h>
+
+#include <asm/asm.h>
+#include <asm/mipsregs.h>
+#include <asm/regdef.h>
+#include <asm/stackframe.h>
+
+/* A lot of complication here is taken away because:
+ *
+ * 1) We handle one interrupt and return, sitting in a loop and moving across
+ * all the pending IRQ bits in the cause register is _NOT_ the answer, the
+ * common case is one pending IRQ so optimize in that direction.
+ *
+ * 2) We need not check against bits in the status register IRQ mask, that
+ * would make this routine slow as hell.
+ *
+ * 3) Linux only thinks in terms of all IRQs on or all IRQs off, nothing in
+ * between like BSD spl() brain-damage.
+ *
+ * Furthermore, the IRQs on the MIPS board look basically (barring software
+ * IRQs which we don't use at all and all external interrupt sources are
+ * combined together on hardware interrupt 0 (MIPS IRQ 2)) like:
+ *
+ * MIPS IRQ Source
+ * -------- ------
+ * 0 Software (ignored)
+ * 1 Software (ignored)
+ * 2 Combined hardware interrupt (hw0)
+ * 3 Hardware (ignored)
+ * 4 Hardware (ignored)
+ * 5 Hardware (ignored)
+ * 6 Hardware (ignored)
+ * 7 R4k timer (what we use)
+ *
+ * Note: On the SEAD board thing are a little bit different.
+ * Here IRQ 2 (hw0) is wired to the UART0 and IRQ 3 (hw1) is wired
+ * wired to UART1.
+ *
+ * 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.
+ */
+
+ .text
+ .set noreorder
+ .set noat
+ .align 5
+ NESTED(mipsIRQ, PT_SIZE, sp)
+ SAVE_ALL
+ CLI
+ .set at
+
+ mfc0 s0, CP0_CAUSE # get irq bits
+ mfc0 s1, CP0_STATUS # get irq mask
+ and s0, s1
+
+ /* First we check for r4k counter/timer IRQ. */
+ andi a0, s0, CAUSEF_IP7
+ beq a0, zero, 1f
+ andi a0, s0, CAUSEF_IP2 # delay slot, check hw0 interrupt
+
+ /* Wheee, a timer interrupt. */
+ move a0, sp
+ jal mips_timer_interrupt
+ nop
+
+ j ret_from_irq
+ nop
+
+1:
+#if defined(CONFIG_MIPS_SEAD)
+ beq a0, zero, 1f
+ andi a0, s0, CAUSEF_IP3 # delay slot, check hw1 interrupt
+#else
+ beq a0, zero, 1f # delay slot, check hw3 interrupt
+ andi a0, s0, CAUSEF_IP5
+#endif
+
+ /* Wheee, combined hardware level zero interrupt. */
+#if defined(CONFIG_MIPS_ATLAS)
+ jal atlas_hw0_irqdispatch
+#elif defined(CONFIG_MIPS_MALTA)
+ jal malta_hw0_irqdispatch
+#elif defined(CONFIG_MIPS_SEAD)
+ jal sead_hw0_irqdispatch
+#else
+#error "MIPS board not supported\n"
+#endif
+ move a0, sp # delay slot
+
+ j ret_from_irq
+ nop # delay slot
+
+1:
+#if defined(CONFIG_MIPS_SEAD)
+ beq a0, zero, 1f
+ andi a0, s0, CAUSEF_IP5 # delay slot, check hw3 interrupt
+ jal sead_hw1_irqdispatch
+ move a0, sp # delay slot
+ j ret_from_irq
+ nop # delay slot
+1:
+#endif
+#if defined(CONFIG_MIPS_MALTA)
+ beq a0, zero, 1f # check hw3 (coreHI) interrupt
+ nop
+ jal corehi_irqdispatch
+ move a0, sp
+ j ret_from_irq
+ nop
+1:
+#endif
+ /*
+ * Here by mistake? This is possible, what can happen is that by the
+ * time we take the exception the IRQ pin goes low, so just leave if
+ * this is the case.
+ */
+ move a1,s0
+ PRINT("Got interrupt: c0_cause = %08x\n")
+ mfc0 a1, CP0_EPC
+ PRINT("c0_epc = %08x\n")
+
+ j ret_from_irq
+ nop
+ END(mipsIRQ)
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