1 files changed, 133 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/fpu.S b/arch/powerpc/kernel/fpu.S
new file mode 100644
index 000000000000..665d7d34304c
--- /dev/null
+++ b/arch/powerpc/kernel/fpu.S
@@ -0,0 +1,133 @@
+/*
+ *  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