summaryrefslogtreecommitdiff
path: root/arch/powerpc/kernel/fpu.S
blob: 665d7d34304cd0118c62c18963600ddbb8070118 (plain)
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
/*
 *  FPU support code, moved here from head.S so that it can be used
 *  by chips which use other head-whatever.S files.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 *
 */

#include <linux/config.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <asm/pgtable.h>
#include <asm/cputable.h>
#include <asm/cache.h>
#include <asm/thread_info.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>

/*
 * This task wants to use the FPU now.
 * On UP, disable FP for the task which had the FPU previously,
 * and save its floating-point registers in its thread_struct.
 * Load up this task's FP registers from its thread_struct,
 * enable the FPU for the current task and return to the task.
 */
	.globl	load_up_fpu
load_up_fpu:
	mfmsr	r5
	ori	r5,r5,MSR_FP
#ifdef CONFIG_PPC64BRIDGE
	clrldi	r5,r5,1			/* turn off 64-bit mode */
#endif /* CONFIG_PPC64BRIDGE */
	SYNC
	MTMSRD(r5)			/* enable use of fpu now */
	isync
/*
 * For SMP, we don't do lazy FPU switching because it just gets too
 * horrendously complex, especially when a task switches from one CPU
 * to another.  Instead we call giveup_fpu in switch_to.
 */
#ifndef CONFIG_SMP
	tophys(r6,0)			/* get __pa constant */
	addis	r3,r6,last_task_used_math@ha
	lwz	r4,last_task_used_math@l(r3)
	cmpwi	0,r4,0
	beq	1f
	add	r4,r4,r6
	addi	r4,r4,THREAD		/* want last_task_used_math->thread */
	SAVE_32FPRS(0, r4)
	mffs	fr0
	stfd	fr0,THREAD_FPSCR-4(r4)
	lwz	r5,PT_REGS(r4)
	add	r5,r5,r6
	lwz	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
	li	r10,MSR_FP|MSR_FE0|MSR_FE1
	andc	r4,r4,r10		/* disable FP for previous task */
	stw	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1:
#endif /* CONFIG_SMP */
	/* enable use of FP after return */
	mfspr	r5,SPRN_SPRG3		/* current task's THREAD (phys) */
	lwz	r4,THREAD_FPEXC_MODE(r5)
	ori	r9,r9,MSR_FP		/* enable FP for current */
	or	r9,r9,r4
	lfd	fr0,THREAD_FPSCR-4(r5)
	mtfsf	0xff,fr0
	REST_32FPRS(0, r5)
#ifndef CONFIG_SMP
	subi	r4,r5,THREAD
	sub	r4,r4,r6
	stw	r4,last_task_used_math@l(r3)
#endif /* CONFIG_SMP */
	/* restore registers and return */
	/* we haven't used ctr or xer or lr */
	b	fast_exception_return

/*
 * FP unavailable trap from kernel - print a message, but let
 * the task use FP in the kernel until it returns to user mode.
 */
 	.globl	KernelFP
KernelFP:
	lwz	r3,_MSR(r1)
	ori	r3,r3,MSR_FP
	stw	r3,_MSR(r1)		/* enable use of FP after return */
	lis	r3,86f@h
	ori	r3,r3,86f@l
	mr	r4,r2			/* current */
	lwz	r5,_NIP(r1)
	bl	printk
	b	ret_from_except
86:	.string	"floating point used in kernel (task=%p, pc=%x)\n"
	.align	4,0

/*
 * giveup_fpu(tsk)
 * Disable FP for the task given as the argument,
 * and save the floating-point registers in its thread_struct.
 * Enables the FPU for use in the kernel on return.
 */
	.globl	giveup_fpu
giveup_fpu:
	mfmsr	r5
	ori	r5,r5,MSR_FP
	SYNC_601
	ISYNC_601
	MTMSRD(r5)			/* enable use of fpu now */
	SYNC_601
	isync
	cmpwi	0,r3,0
	beqlr-				/* if no previous owner, done */
	addi	r3,r3,THREAD	        /* want THREAD of task */
	lwz	r5,PT_REGS(r3)
	cmpwi	0,r5,0
	SAVE_32FPRS(0, r3)
	mffs	fr0
	stfd	fr0,THREAD_FPSCR-4(r3)
	beq	1f
	lwz	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
	li	r3,MSR_FP|MSR_FE0|MSR_FE1
	andc	r4,r4,r3		/* disable FP for previous task */
	stw	r4,_MSR-STACK_FRAME_OVERHEAD(r5)
1:
#ifndef CONFIG_SMP
	li	r5,0
	lis	r4,last_task_used_math@ha
	stw	r5,last_task_used_math@l(r4)
#endif /* CONFIG_SMP */
	blr