Support for the NEC DDB Vrc-5074 evaluation board. Patches by

Geert Uytterhoeven (geert@linux-m68k.org).

1 files changed, 122 insertions, 0 deletions

diff --git a/arch/mips/ddb5074/int-handler.S b/arch/mips/ddb5074/int-handler.S
new file mode 100644
index 000000000..07d091953
--- /dev/null
+++ b/arch/mips/ddb5074/int-handler.S
@@ -0,0 +1,122 @@
+/*
+ *  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>
+ *
+ *  $Id$
+ */
+
+#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)