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 31load_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) 621: 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 86KernelFP: 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 9686: .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 106giveup_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) 1271: 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 134