diff options
Diffstat (limited to 'arch/mips/kernel/r4k_switch.S')
| -rw-r--r-- | arch/mips/kernel/r4k_switch.S | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/arch/mips/kernel/r4k_switch.S b/arch/mips/kernel/r4k_switch.S new file mode 100644 index 00000000..9414f935 --- /dev/null +++ b/arch/mips/kernel/r4k_switch.S @@ -0,0 +1,252 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * Copyright (C) 1994, 1995, 1996, 1998, 1999, 2002, 2003 Ralf Baechle + * Copyright (C) 1996 David S. Miller (davem@davemloft.net) + * Copyright (C) 1994, 1995, 1996, by Andreas Busse + * Copyright (C) 1999 Silicon Graphics, Inc. + * Copyright (C) 2000 MIPS Technologies, Inc. + * written by Carsten Langgaard, carstenl@mips.com + */ +#include <asm/asm.h> +#include <asm/cachectl.h> +#include <asm/fpregdef.h> +#include <asm/mipsregs.h> +#include <asm/asm-offsets.h> +#include <asm/page.h> +#include <asm/pgtable-bits.h> +#include <asm/regdef.h> +#include <asm/stackframe.h> +#include <asm/thread_info.h> + +#include <asm/asmmacro.h> + +/* + * Offset to the current process status flags, the first 32 bytes of the + * stack are not used. + */ +#define ST_OFF (_THREAD_SIZE - 32 - PT_SIZE + PT_STATUS) + +/* + * FPU context is saved iff the process has used it's FPU in the current + * time slice as indicated by _TIF_USEDFPU. In any case, the CU1 bit for user + * space STATUS register should be 0, so that a process *always* starts its + * userland with FPU disabled after each context switch. + * + * FPU will be enabled as soon as the process accesses FPU again, through + * do_cpu() trap. + */ + +/* + * task_struct *resume(task_struct *prev, task_struct *next, + * struct thread_info *next_ti) + */ + .align 5 + LEAF(resume) + mfc0 t1, CP0_STATUS + LONG_S t1, THREAD_STATUS(a0) + cpu_save_nonscratch a0 + LONG_S ra, THREAD_REG31(a0) + + /* + * check if we need to save FPU registers + */ + PTR_L t3, TASK_THREAD_INFO(a0) + LONG_L t0, TI_FLAGS(t3) + li t1, _TIF_USEDFPU + and t2, t0, t1 + beqz t2, 1f + nor t1, zero, t1 + + and t0, t0, t1 + LONG_S t0, TI_FLAGS(t3) + + /* + * clear saved user stack CU1 bit + */ + LONG_L t0, ST_OFF(t3) + li t1, ~ST0_CU1 + and t0, t0, t1 + LONG_S t0, ST_OFF(t3) + + fpu_save_double a0 t0 t1 # c0_status passed in t0 + # clobbers t1 +1: + + /* + * The order of restoring the registers takes care of the race + * updating $28, $29 and kernelsp without disabling ints. + */ + move $28, a2 + cpu_restore_nonscratch a1 + + PTR_ADDU t0, $28, _THREAD_SIZE - 32 + set_saved_sp t0, t1, t2 +#ifdef CONFIG_MIPS_MT_SMTC + /* Read-modify-writes of Status must be atomic on a VPE */ + mfc0 t2, CP0_TCSTATUS + ori t1, t2, TCSTATUS_IXMT + mtc0 t1, CP0_TCSTATUS + andi t2, t2, TCSTATUS_IXMT + _ehb + DMT 8 # dmt t0 + move t1,ra + jal mips_ihb + move ra,t1 +#endif /* CONFIG_MIPS_MT_SMTC */ + mfc0 t1, CP0_STATUS /* Do we really need this? */ + li a3, 0xff01 + and t1, a3 + LONG_L a2, THREAD_STATUS(a1) + nor a3, $0, a3 + and a2, a3 + or a2, t1 + mtc0 a2, CP0_STATUS +#ifdef CONFIG_MIPS_MT_SMTC + _ehb + andi t0, t0, VPECONTROL_TE + beqz t0, 1f + emt +1: + mfc0 t1, CP0_TCSTATUS + xori t1, t1, TCSTATUS_IXMT + or t1, t1, t2 + mtc0 t1, CP0_TCSTATUS + _ehb +#endif /* CONFIG_MIPS_MT_SMTC */ + move v0, a0 + jr ra + END(resume) + +/* + * Save a thread's fp context. + */ +LEAF(_save_fp) +#ifdef CONFIG_64BIT + mfc0 t0, CP0_STATUS +#endif + fpu_save_double a0 t0 t1 # clobbers t1 + jr ra + END(_save_fp) + +/* + * Restore a thread's fp context. + */ +LEAF(_restore_fp) +#ifdef CONFIG_64BIT + mfc0 t0, CP0_STATUS +#endif + fpu_restore_double a0 t0 t1 # clobbers t1 + jr ra + END(_restore_fp) + +/* + * Load the FPU with signalling NANS. This bit pattern we're using has + * the property that no matter whether considered as single or as double + * precision represents signaling NANS. + * + * We initialize fcr31 to rounding to nearest, no exceptions. + */ + +#define FPU_DEFAULT 0x00000000 + +LEAF(_init_fpu) +#ifdef CONFIG_MIPS_MT_SMTC + /* Rather than manipulate per-VPE Status, set per-TC bit in TCStatus */ + mfc0 t0, CP0_TCSTATUS + /* Bit position is the same for Status, TCStatus */ + li t1, ST0_CU1 + or t0, t1 + mtc0 t0, CP0_TCSTATUS +#else /* Normal MIPS CU1 enable */ + mfc0 t0, CP0_STATUS + li t1, ST0_CU1 + or t0, t1 + mtc0 t0, CP0_STATUS +#endif /* CONFIG_MIPS_MT_SMTC */ + enable_fpu_hazard + + li t1, FPU_DEFAULT + ctc1 t1, fcr31 + + li t1, -1 # SNaN + +#ifdef CONFIG_64BIT + sll t0, t0, 5 + bgez t0, 1f # 16 / 32 register mode? + + dmtc1 t1, $f1 + dmtc1 t1, $f3 + dmtc1 t1, $f5 + dmtc1 t1, $f7 + dmtc1 t1, $f9 + dmtc1 t1, $f11 + dmtc1 t1, $f13 + dmtc1 t1, $f15 + dmtc1 t1, $f17 + dmtc1 t1, $f19 + dmtc1 t1, $f21 + dmtc1 t1, $f23 + dmtc1 t1, $f25 + dmtc1 t1, $f27 + dmtc1 t1, $f29 + dmtc1 t1, $f31 +1: +#endif + +#ifdef CONFIG_CPU_MIPS32 + mtc1 t1, $f0 + mtc1 t1, $f1 + mtc1 t1, $f2 + mtc1 t1, $f3 + mtc1 t1, $f4 + mtc1 t1, $f5 + mtc1 t1, $f6 + mtc1 t1, $f7 + mtc1 t1, $f8 + mtc1 t1, $f9 + mtc1 t1, $f10 + mtc1 t1, $f11 + mtc1 t1, $f12 + mtc1 t1, $f13 + mtc1 t1, $f14 + mtc1 t1, $f15 + mtc1 t1, $f16 + mtc1 t1, $f17 + mtc1 t1, $f18 + mtc1 t1, $f19 + mtc1 t1, $f20 + mtc1 t1, $f21 + mtc1 t1, $f22 + mtc1 t1, $f23 + mtc1 t1, $f24 + mtc1 t1, $f25 + mtc1 t1, $f26 + mtc1 t1, $f27 + mtc1 t1, $f28 + mtc1 t1, $f29 + mtc1 t1, $f30 + mtc1 t1, $f31 +#else + .set mips3 + dmtc1 t1, $f0 + dmtc1 t1, $f2 + dmtc1 t1, $f4 + dmtc1 t1, $f6 + dmtc1 t1, $f8 + dmtc1 t1, $f10 + dmtc1 t1, $f12 + dmtc1 t1, $f14 + dmtc1 t1, $f16 + dmtc1 t1, $f18 + dmtc1 t1, $f20 + dmtc1 t1, $f22 + dmtc1 t1, $f24 + dmtc1 t1, $f26 + dmtc1 t1, $f28 + dmtc1 t1, $f30 +#endif + jr ra + END(_init_fpu) |