1 files changed, 118 insertions, 0 deletions

diff --git a/arch/mips/sgi-ip22/ip22-irq.S b/arch/mips/sgi-ip22/ip22-irq.S
new file mode 100644
index 000000000000..6ccbd9e1d967
--- /dev/null
+++ b/arch/mips/sgi-ip22/ip22-irq.S
@@ -0,0 +1,118 @@
+/*
+ * 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)