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-rw-r--r--arch/mips/sgi-ip22/ip22-irq.S118
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diff --git a/arch/mips/sgi-ip22/ip22-irq.S b/arch/mips/sgi-ip22/ip22-irq.S
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+/*
+ * ip22-irq.S: Interrupt exception dispatch code for FullHouse and
+ * Guiness.
+ *
+ * Copyright (C) 1996 David S. Miller (dm@engr.sgi.com)
+ */
+
+#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(indyIRQ, PT_SIZE, sp)
+ SAVE_ALL
+ CLI
+ .set at
+ mfc0 s0, CP0_CAUSE # get irq mask
+
+ /* 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 local level zero
+
+ /* Wheee, a timer interrupt. */
+ jal indy_r4k_timer_interrupt
+ move a0, sp # delay slot
+ j ret_from_irq
+ nop # delay slot
+
+1:
+ beq a0, zero, 1f
+ andi a0, s0, CAUSEF_IP3 # delay slot, check local level one
+
+ /* Wheee, local level zero interrupt. */
+ jal indy_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. */
+ jal indy_local1_irqdispatch
+ move a0, sp # delay slot
+ j ret_from_irq
+ nop # delay slot
+
+1:
+ beq a0, zero, 1f
+ andi a0, s0, (CAUSEF_IP4 | CAUSEF_IP5) # delay slot
+
+ /* Wheee, an asynchronous bus error... */
+ jal indy_buserror_irq
+ move a0, sp # delay slot
+ j ret_from_irq
+ nop # delay slot
+
+1:
+ /* Here by mistake? It is possible, that by the time we take
+ * the exception the IRQ pin goes low, so just leave if this
+ * is the case.
+ */
+ beq a0, zero, 1f
+ nop # delay slot
+
+ /* Must be one of the 8254 timers... */
+ jal indy_8254timer_irq
+ move a0, sp # delay slot
+1:
+ j ret_from_irq
+ nop # delay slot
+ END(indyIRQ)