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/*
* arch/mips/ddb5074/int-handler.S -- NEC DDB Vrc-5074 interrupt handler
*
* Based on arch/mips/sgi/kernel/indyIRQ.S
*
* Copyright (C) 1996 David S. Miller (dm@engr.sgi.com)
*
* Copyright (C) 2000 Geert Uytterhoeven <geert@sonycom.com>
* Sony Software Development Center Europe (SDCE), Brussels
*/
#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 INDY look basically (barring software IRQs
* which we don't use at all) like:
*
* MIPS IRQ Source
* -------- ------
* 0 Software (ignored)
* 1 Software (ignored)
* 2 Local IRQ level zero
* 3 Local IRQ level one
* 4 8254 Timer zero
* 5 8254 Timer one
* 6 Bus Error
* 7 R4k timer (what we use)
*
* We handle the IRQ according to _our_ priority which is:
*
* Highest ---- R4k Timer
* Local IRQ zero
* Local IRQ one
* Bus Error
* 8254 Timer zero
* Lowest ---- 8254 Timer one
*
* 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(ddbIRQ, PT_SIZE, sp)
SAVE_ALL
CLI
.set at
mfc0 s0, CP0_CAUSE # get irq mask
#if 1
mfc0 t2,CP0_STATUS # get enabled interrupts
and s0,t2 # isolate allowed ones
#endif
/* First we check for r4k counter/timer IRQ. */
andi a0, s0, CAUSEF_IP2 # delay slot, check local level zero
beq a0, zero, 1f
andi a0, s0, CAUSEF_IP3 # delay slot, check local level one
/* Wheee, local level zero interrupt. */
jal ddb_local0_irqdispatch
move a0, sp # delay slot
j ret_from_irq
nop # delay slot
1:
beq a0, zero, 1f
andi a0, s0, CAUSEF_IP6 # delay slot, check bus error
/* Wheee, local level one interrupt. */
move a0, sp
jal ddb_local1_irqdispatch
nop
j ret_from_irq
nop
1:
beq a0, zero, 1f
nop
/* Wheee, an asynchronous bus error... */
move a0, sp
jal ddb_buserror_irq
nop
j ret_from_irq
nop
1:
/* 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.
*/
andi a0, s0, (CAUSEF_IP4 | CAUSEF_IP5)
beq a0, zero, 1f
/* Must be one of the 8254 timers... */
move a0, sp
jal ddb_8254timer_irq
nop
1:
j ret_from_irq
nop
END(ddbIRQ)
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