r2300_switch.S
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/*
* r2300_switch.S: R2300 specific task switching code.
*
* Copyright (C) 1994, 1995, 1996, 1999 by Ralf Baechle
* Copyright (C) 1994, 1995, 1996 by Andreas Busse
*
* Multi-cpu abstraction and macros for easier reading:
* Copyright (C) 1996 David S. Miller (davem@davemloft.net)
*
* Further modifications to make this work:
* Copyright (c) 1998-2000 Harald Koerfgen
*/
#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/regdef.h>
#include <asm/stackframe.h>
#include <asm/thread_info.h>
#include <asm/asmmacro.h>
.set mips1
.align 5
/*
* 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) )
*/
LEAF(resume)
mfc0 t1, CP0_STATUS
sw t1, THREAD_STATUS(a0)
cpu_save_nonscratch a0
sw ra, THREAD_REG31(a0)
/*
* check if we need to save FPU registers
*/
lw t3, TASK_THREAD_INFO(a0)
lw t0, TI_FLAGS(t3)
li t1, _TIF_USEDFPU
and t2, t0, t1
beqz t2, 1f
nor t1, zero, t1
and t0, t0, t1
sw t0, TI_FLAGS(t3)
/*
* clear saved user stack CU1 bit
*/
lw t0, ST_OFF(t3)
li t1, ~ST0_CU1
and t0, t0, t1
sw t0, ST_OFF(t3)
fpu_save_single a0, t0 # clobbers t0
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
addiu t1, $28, _THREAD_SIZE - 32
sw t1, kernelsp
mfc0 t1, CP0_STATUS /* Do we really need this? */
li a3, 0xff01
and t1, a3
lw a2, THREAD_STATUS(a1)
nor a3, $0, a3
and a2, a3
or a2, t1
mtc0 a2, CP0_STATUS
move v0, a0
jr ra
END(resume)
/*
* Save a thread's fp context.
*/
LEAF(_save_fp)
fpu_save_single a0, t1 # clobbers t1
jr ra
END(_save_fp)
/*
* Restore a thread's fp context.
*/
LEAF(_restore_fp)
fpu_restore_single a0, 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)
mfc0 t0, CP0_STATUS
li t1, ST0_CU1
or t0, t1
mtc0 t0, CP0_STATUS
li t1, FPU_DEFAULT
ctc1 t1, fcr31
li t0, -1
mtc1 t0, $f0
mtc1 t0, $f1
mtc1 t0, $f2
mtc1 t0, $f3
mtc1 t0, $f4
mtc1 t0, $f5
mtc1 t0, $f6
mtc1 t0, $f7
mtc1 t0, $f8
mtc1 t0, $f9
mtc1 t0, $f10
mtc1 t0, $f11
mtc1 t0, $f12
mtc1 t0, $f13
mtc1 t0, $f14
mtc1 t0, $f15
mtc1 t0, $f16
mtc1 t0, $f17
mtc1 t0, $f18
mtc1 t0, $f19
mtc1 t0, $f20
mtc1 t0, $f21
mtc1 t0, $f22
mtc1 t0, $f23
mtc1 t0, $f24
mtc1 t0, $f25
mtc1 t0, $f26
mtc1 t0, $f27
mtc1 t0, $f28
mtc1 t0, $f29
mtc1 t0, $f30
mtc1 t0, $f31
jr ra
END(_init_fpu)