aboutsummaryrefslogtreecommitdiffstats
path: root/arch/mips/mips-boards/sim/sim_IRQ.c
blob: 9987a85aabeb36f87f3f6a3c75c0517750dea7fd (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
/*
 * 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)
 *
 * Note: On the SEAD board thing are a little bit different.
 *       Here IRQ 2 (hw0) is wired to the UART0 and IRQ 3 (hw1) is wired
 *       wired to UART1.
 *
 * 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 bits
	mfc0	s1, CP0_STATUS		# get irq mask
	and	s0, s1

	/* 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:
#if defined(CONFIG_MIPS_SEAD)
	beq	a0, zero, 1f
	 andi	a0, s0, CAUSEF_IP3	# delay slot, check hw1 interrupt
#else
	beq	a0, zero, 1f		# delay slot, check hw3 interrupt
 	 andi	a0, s0, CAUSEF_IP5
#endif

	/* Wheee, combined hardware level zero interrupt. */
#if defined(CONFIG_MIPS_ATLAS)
	jal	atlas_hw0_irqdispatch
#elif defined(CONFIG_MIPS_MALTA)
	jal	malta_hw0_irqdispatch
#elif defined(CONFIG_MIPS_SEAD)
	jal	sead_hw0_irqdispatch
#else
#error "MIPS board not supported\n"
#endif
	 move	a0, sp			# delay slot

	j	ret_from_irq
	 nop				# delay slot

1:
#if defined(CONFIG_MIPS_SEAD)
	beq	a0, zero, 1f
	 andi	a0, s0, CAUSEF_IP5	# delay slot, check hw3 interrupt
	jal	sead_hw1_irqdispatch
	 move	a0, sp			# delay slot
	j	ret_from_irq
	 nop				# delay slot
1:
#endif
#if defined(CONFIG_MIPS_MALTA)
	beq	a0, zero, 1f            # check hw3 (coreHI) interrupt
	 nop
	jal	corehi_irqdispatch
	 move	a0, sp
	j	ret_from_irq
	 nop
1:
#endif
	/*
	 * 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)