patch-2.4.4 linux/arch/mips/mips-boards/generic/mipsIRQ.S

• Lines: 123
• Date: Fri Apr 13 20:26:07 2001
• Orig file: v2.4.3/linux/arch/mips/mips-boards/generic/mipsIRQ.S
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.3/linux/arch/mips/mips-boards/generic/mipsIRQ.S linux/arch/mips/mips-boards/generic/mipsIRQ.S
@@ -0,0 +1,122 @@
+/*
+ * Carsten Langgaard, carstenl@mips.com
+ * Copyright (C) 1999, 2000 MIPS Technologies, Inc.  All rights reserved.
+ *
+ * ########################################################################
+ *
+ *  This program is free software; you can distribute it and/or modify it
+ *  under the terms of the GNU General Public License (Version 2) as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
+ *
+ * ########################################################################
+ *
+ * Interrupt exception dispatch code.
+ *
+ */
+#include <linux/config.h>
+
+#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 MIPS board look basically (barring software
+ * IRQs which we don't use at all and all external interrupt sources are
+ * combined together on hardware interrupt 0 (MIPS IRQ 2)) like:
+ *
+ *	MIPS IRQ	Source
+ *      --------        ------
+ *             0	Software (ignored)
+ *             1        Software (ignored)
+ *             2        Combined hardware interrupt (hw0)
+ *             3        Hardware (ignored)
+ *             4        Hardware (ignored)
+ *             5        Hardware (ignored)
+ *             6        Hardware (ignored)
+ *             7        R4k timer (what we use)
+ *
+ * We handle the IRQ according to _our_ priority which is:
+ *
+ * Highest ----     R4k Timer
+ * Lowest  ----     Combined hardware interrupt
+ *
+ * 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(mipsIRQ, 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 hw0 interrupt
+
+	/* Wheee, a timer interrupt. */
+	move	a0, sp
+	jal	mips_timer_interrupt
+	 nop
+
+	j	ret_from_irq
+	 nop
+
+1:
+	beq	a0, zero, 1f
+	 nop
+
+	/* Wheee, combined hardware level zero interrupt. */
+#if defined(CONFIG_MIPS_ATLAS)
+	jal	atlas_hw0_irqdispatch
+#elif defined(CONFIG_MIPS_MALTA)
+	jal	malta_hw0_irqdispatch
+#else
+#error "MIPS board not supported\n"	
+#endif
+	 move	a0, sp			# delay slot
+
+	j	ret_from_irq
+	 nop				# delay slot
+
+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.
+	 */
+	move	a1,s0
+	PRINT("Got interrupt: c0_cause = %08x\n")
+	mfc0	a1, CP0_EPC
+	PRINT("c0_epc = %08x\n")
+
+	j	ret_from_irq
+	 nop
+	END(mipsIRQ)