Merge branch 'for-linus' from kernel.org:/.../shaggy/jfs-2.6 manually
[linux-2.6] / arch / ppc / kernel / fpu.S
1 /*
2  *  FPU support code, moved here from head.S so that it can be used
3  *  by chips which use other head-whatever.S files.
4  *
5  *  This program is free software; you can redistribute it and/or
6  *  modify it under the terms of the GNU General Public License
7  *  as published by the Free Software Foundation; either version
8  *  2 of the License, or (at your option) any later version.
9  *
10  */
11
12 #include <linux/config.h>
13 #include <asm/processor.h>
14 #include <asm/page.h>
15 #include <asm/mmu.h>
16 #include <asm/pgtable.h>
17 #include <asm/cputable.h>
18 #include <asm/cache.h>
19 #include <asm/thread_info.h>
20 #include <asm/ppc_asm.h>
21 #include <asm/asm-offsets.h>
22
23 /*
24  * This task wants to use the FPU now.
25  * On UP, disable FP for the task which had the FPU previously,
26  * and save its floating-point registers in its thread_struct.
27  * Load up this task's FP registers from its thread_struct,
28  * enable the FPU for the current task and return to the task.
29  */
30         .globl  load_up_fpu
31 load_up_fpu:
32         mfmsr   r5
33         ori     r5,r5,MSR_FP
34 #ifdef CONFIG_PPC64BRIDGE
35         clrldi  r5,r5,1                 /* turn off 64-bit mode */
36 #endif /* CONFIG_PPC64BRIDGE */
37         SYNC
38         MTMSRD(r5)                      /* enable use of fpu now */
39         isync
40 /*
41  * For SMP, we don't do lazy FPU switching because it just gets too
42  * horrendously complex, especially when a task switches from one CPU
43  * to another.  Instead we call giveup_fpu in switch_to.
44  */
45 #ifndef CONFIG_SMP
46         tophys(r6,0)                    /* get __pa constant */
47         addis   r3,r6,last_task_used_math@ha
48         lwz     r4,last_task_used_math@l(r3)
49         cmpwi   0,r4,0
50         beq     1f
51         add     r4,r4,r6
52         addi    r4,r4,THREAD            /* want last_task_used_math->thread */
53         SAVE_32FPRS(0, r4)
54         mffs    fr0
55         stfd    fr0,THREAD_FPSCR-4(r4)
56         lwz     r5,PT_REGS(r4)
57         add     r5,r5,r6
58         lwz     r4,_MSR-STACK_FRAME_OVERHEAD(r5)
59         li      r10,MSR_FP|MSR_FE0|MSR_FE1
60         andc    r4,r4,r10               /* disable FP for previous task */
61         stw     r4,_MSR-STACK_FRAME_OVERHEAD(r5)
62 1:
63 #endif /* CONFIG_SMP */
64         /* enable use of FP after return */
65         mfspr   r5,SPRN_SPRG3           /* current task's THREAD (phys) */
66         lwz     r4,THREAD_FPEXC_MODE(r5)
67         ori     r9,r9,MSR_FP            /* enable FP for current */
68         or      r9,r9,r4
69         lfd     fr0,THREAD_FPSCR-4(r5)
70         mtfsf   0xff,fr0
71         REST_32FPRS(0, r5)
72 #ifndef CONFIG_SMP
73         subi    r4,r5,THREAD
74         sub     r4,r4,r6
75         stw     r4,last_task_used_math@l(r3)
76 #endif /* CONFIG_SMP */
77         /* restore registers and return */
78         /* we haven't used ctr or xer or lr */
79         b       fast_exception_return
80
81 /*
82  * FP unavailable trap from kernel - print a message, but let
83  * the task use FP in the kernel until it returns to user mode.
84  */
85         .globl  KernelFP
86 KernelFP:
87         lwz     r3,_MSR(r1)
88         ori     r3,r3,MSR_FP
89         stw     r3,_MSR(r1)             /* enable use of FP after return */
90         lis     r3,86f@h
91         ori     r3,r3,86f@l
92         mr      r4,r2                   /* current */
93         lwz     r5,_NIP(r1)
94         bl      printk
95         b       ret_from_except
96 86:     .string "floating point used in kernel (task=%p, pc=%x)\n"
97         .align  4,0
98
99 /*
100  * giveup_fpu(tsk)
101  * Disable FP for the task given as the argument,
102  * and save the floating-point registers in its thread_struct.
103  * Enables the FPU for use in the kernel on return.
104  */
105         .globl  giveup_fpu
106 giveup_fpu:
107         mfmsr   r5
108         ori     r5,r5,MSR_FP
109         SYNC_601
110         ISYNC_601
111         MTMSRD(r5)                      /* enable use of fpu now */
112         SYNC_601
113         isync
114         cmpwi   0,r3,0
115         beqlr-                          /* if no previous owner, done */
116         addi    r3,r3,THREAD            /* want THREAD of task */
117         lwz     r5,PT_REGS(r3)
118         cmpwi   0,r5,0
119         SAVE_32FPRS(0, r3)
120         mffs    fr0
121         stfd    fr0,THREAD_FPSCR-4(r3)
122         beq     1f
123         lwz     r4,_MSR-STACK_FRAME_OVERHEAD(r5)
124         li      r3,MSR_FP|MSR_FE0|MSR_FE1
125         andc    r4,r4,r3                /* disable FP for previous task */
126         stw     r4,_MSR-STACK_FRAME_OVERHEAD(r5)
127 1:
128 #ifndef CONFIG_SMP
129         li      r5,0
130         lis     r4,last_task_used_math@ha
131         stw     r5,last_task_used_math@l(r4)
132 #endif /* CONFIG_SMP */
133         blr