patch-2.4.19 linux-2.4.19/arch/mips/sgi-ip22/ip22-irq.S

• Lines: 126
• Date: Fri Aug 2 17:39:43 2002
• Orig file: linux-2.4.18/arch/mips/sgi-ip22/ip22-irq.S
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.18/arch/mips/sgi-ip22/ip22-irq.S linux-2.4.19/arch/mips/sgi-ip22/ip22-irq.S
@@ -0,0 +1,125 @@
+/*
+ * 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. */
+	move	a0, sp
+	jal	indy_r4k_timer_interrupt
+	 nop				# 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. */
+	move	a0, sp
+	jal	indy_local1_irqdispatch
+	 nop
+
+	j	ret_from_irq
+	 nop
+
+1:
+	beq	a0, zero, 1f
+	 nop
+
+	/* Wheee, an asynchronous bus error... */
+	move	a0, sp
+	jal	indy_buserror_irq
+	 nop
+
+	j	ret_from_irq
+	 nop
+
+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.
+	 */
+	andi	a0, s0, (CAUSEF_IP4 | CAUSEF_IP5)
+	beq	a0, zero, 1f
+
+	/* Must be one of the 8254 timers... */
+	move	a0, sp
+	jal	indy_8254timer_irq
+	 nop
+1:
+	j	ret_from_irq
+	 nop
+	END(indyIRQ)