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MIPS: Tidy up FPU context switching 

Rather than saving the scalar FP or vector context in the assembly
resume function, reuse the existing C code we have in fpu.h to do
exactly that. This reduces duplication, results in a much easier to read
resume function & should allow the compiler to optimise out more MSA
code due to is_msa_enabled()/cpu_has_msa being known-zero at compile
time for kernels without MSA support.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-kernel@vger.kernel.org
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Patchwork: https://patchwork.linux-mips.org/patch/10830/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2015-08-03 08:49:30 -07:00 committed by Ralf Baechle
parent 23eb6f4016
commit 1a3d59579b
3 changed files with 18 additions and 65 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
arch/mips/include/asm/fpu.h
View File

@ -164,25 +164,30 @@ static inline int own_fpu(int restore)
return ret;
}
static inline void lose_fpu(int save)
static inline void lose_fpu_inatomic(int save, struct task_struct *tsk)
{
preempt_disable();
if (is_msa_enabled()) {
if (save) {
save_msa(current);
current->thread.fpu.fcr31 =
save_msa(tsk);
tsk->thread.fpu.fcr31 =
read_32bit_cp1_register(CP1_STATUS);
}
disable_msa();
clear_thread_flag(TIF_USEDMSA);
clear_tsk_thread_flag(tsk, TIF_USEDMSA);
__disable_fpu();
} else if (is_fpu_owner()) {
if (save)
_save_fp(current);
_save_fp(tsk);
__disable_fpu();
}
KSTK_STATUS(current) &= ~ST0_CU1;
clear_thread_flag(TIF_USEDFPU);
KSTK_STATUS(tsk) &= ~ST0_CU1;
clear_tsk_thread_flag(tsk, TIF_USEDFPU);
}
static inline void lose_fpu(int save)
{
preempt_disable();
lose_fpu_inatomic(save, current);
preempt_enable();
}

21
arch/mips/include/asm/switch_to.h
View File

@ -16,29 +16,21 @@
#include <asm/watch.h>
#include <asm/dsp.h>
#include <asm/cop2.h>
#include <asm/msa.h>
#include <asm/fpu.h>
struct task_struct;
enum {
FP_SAVE_NONE = 0,
FP_SAVE_VECTOR = -1,
FP_SAVE_SCALAR = 1,
};
/**
* resume - resume execution of a task
* @prev: The task previously executed.
* @next: The task to begin executing.
* @next_ti: task_thread_info(next).
* @fp_save: Which, if any, FP context to save for prev.
*
* This function is used whilst scheduling to save the context of prev & load
* the context of next. Returns prev.
*/
extern asmlinkage struct task_struct *resume(struct task_struct *prev,
struct task_struct *next, struct thread_info *next_ti,
s32 fp_save);
struct task_struct *next, struct thread_info *next_ti);
extern unsigned int ll_bit;
extern struct task_struct *ll_task;
@ -91,8 +83,8 @@ do { if (cpu_has_rw_llb) { \
*/
#define switch_to(prev, next, last) \
do { \
s32 __fpsave = FP_SAVE_NONE; \
__mips_mt_fpaff_switch_to(prev); \
lose_fpu_inatomic(1, prev); \
if (cpu_has_dsp) { \
__save_dsp(prev); \
__restore_dsp(next); \
@ -111,15 +103,10 @@ do { \
clear_c0_status(ST0_CU2); \
} \
__clear_software_ll_bit(); \
if (test_and_clear_tsk_thread_flag(prev, TIF_USEDFPU)) \
__fpsave = FP_SAVE_SCALAR; \
if (test_and_clear_tsk_thread_flag(prev, TIF_USEDMSA)) \
__fpsave = FP_SAVE_VECTOR; \
if (cpu_has_userlocal) \
write_c0_userlocal(task_thread_info(next)->tp_value); \
__restore_watch(); \
disable_msa(); \
(last) = resume(prev, next, task_thread_info(next), __fpsave); \
(last) = resume(prev, next, task_thread_info(next)); \
} while (0)
#endif /* _ASM_SWITCH_TO_H */

41
arch/mips/kernel/r4k_switch.S
View File

@ -34,7 +34,7 @@
#ifndef USE_ALTERNATE_RESUME_IMPL
/*
* task_struct *resume(task_struct *prev, task_struct *next,
* struct thread_info *next_ti, s32 fp_save)
* struct thread_info *next_ti)
*/
.align 5
LEAF(resume)
@ -43,45 +43,6 @@
cpu_save_nonscratch a0
LONG_S ra, THREAD_REG31(a0)
/*
* Check whether we need to save any FP context. FP context is saved
* iff the process has used the context with the scalar FPU or the MSA
* ASE in the current time slice, as indicated by _TIF_USEDFPU and
* _TIF_USEDMSA respectively. switch_to will have set fp_save
* accordingly to an FP_SAVE_ enum value.
*/
beqz a3, 2f
/*
* We do. Clear the saved CU1 bit for prev, such that next time it is
* scheduled it will start in userland with the FPU disabled. If the
* task uses the FPU then it will be enabled again via the do_cpu trap.
* This allows us to lazily restore the FP context.
*/
PTR_L t3, TASK_THREAD_INFO(a0)
LONG_L t0, ST_OFF(t3)
li t1, ~ST0_CU1
and t0, t0, t1
LONG_S t0, ST_OFF(t3)
/* Check whether we're saving scalar or vector context. */
bgtz a3, 1f
/* Save 128b MSA vector context + scalar FP control & status. */
.set push
SET_HARDFLOAT
cfc1 t1, fcr31
msa_save_all a0
.set pop /* SET_HARDFLOAT */
sw t1, THREAD_FCR31(a0)
b 2f
1: /* Save 32b/64b scalar FP context. */
fpu_save_double a0 t0 t1 # c0_status passed in t0
# clobbers t1
2:
#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)
PTR_LA t8, __stack_chk_guard
LONG_L t9, TASK_STACK_CANARY(a1)