linux/arch/mips/kernel/r2300_switch.S
Paul Burton 085c2f25d3 MIPS: Fix R2300 FP context switch handling
Commit 1a3d59579b ("MIPS: Tidy up FPU context switching") removed FP
context saving from the asm-written resume function in favour of reusing
existing code to perform the same task. However it only removed the FP
context saving code from the r4k_switch.S implementation of resume.
Remove it from the r2300_switch.S implementation too in order to prevent
attempting to save the FP context twice, which would likely lead to an
exception from the second save because the FPU had already been disabled
by the first save.

This patch has only been build tested, using rbtx49xx_defconfig.

Fixes: 1a3d59579b ("MIPS: Tidy up FPU context switching")
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-kernel@vger.kernel.org
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/11167/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2015-10-02 19:16:46 +02:00

144 lines
2.7 KiB
ArmAsm

/*
* 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/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)
/*
* 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)
#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
PTR_LA t8, __stack_chk_guard
LONG_L t9, TASK_STACK_CANARY(a1)
LONG_S t9, 0(t8)
#endif
/*
* 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.
*
* The value to initialize fcr31 to comes in $a0.
*/
.set push
SET_HARDFLOAT
LEAF(_init_fpu)
mfc0 t0, CP0_STATUS
li t1, ST0_CU1
or t0, t1
mtc0 t0, CP0_STATUS
ctc1 a0, 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)
.set pop