Commit f45ba2bd authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARCv2: fpu: preserve userspace fpu state 



Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent f05523aa

arch/arc/Kconfig

+5 −10
Original line number Diff line number Diff line
@@ -351,9 +351,8 @@ config NODES_SHIFT 
	  Accessing memory beyond 1GB (with or w/o PAE) requires 2 memory

	  zones.



if ISA_ARCOMPACT



config ARC_COMPACT_IRQ_LEVELS

	depends on ISA_ARCOMPACT

	bool "Setup Timer IRQ as high Priority"

	# if SMP, LV2 enabled ONLY if ARC implementation has LV2 re-entrancy

	depends on !SMP
@@ -361,14 +360,10 @@ config ARC_COMPACT_IRQ_LEVELS 
config ARC_FPU_SAVE_RESTORE

	bool "Enable FPU state persistence across context switch"

	help

	  Double Precision Floating Point unit had dedicated regs which

	  need to be saved/restored across context-switch.

	  Note that ARC FPU is overly simplistic, unlike say x86, which has

	  hardware pieces to allow software to conditionally save/restore,

	  based on actual usage of FPU by a task. Thus our implemn does

	  this for all tasks in system.



endif #ISA_ARCOMPACT

	  ARCompact FPU has internal registers to assist with Double precision

	  Floating Point operations. There are control and stauts registers

	  for floating point exceptions and rounding modes. These are

	  preserved across task context switch when enabled.



config ARC_CANT_LLSC

	def_bool n

arch/arc/include/asm/arcregs.h

+2 −0
Original line number Diff line number Diff line
@@ -39,6 +39,8 @@ 
#define ARC_REG_CLUSTER_BCR	0xcf

#define ARC_REG_AUX_ICCM	0x208	/* ICCM Base Addr (ARCv2) */

#define ARC_REG_LPB_CTRL	0x488	/* ARCv2 Loop Buffer control */

#define ARC_REG_FPU_CTRL	0x300

#define ARC_REG_FPU_STATUS	0x301



/* Common for ARCompact and ARCv2 status register */

#define ARC_REG_STATUS32	0x0A

arch/arc/include/asm/fpu.h

+27 −1
Original line number Diff line number Diff line
@@ -11,6 +11,8 @@ 


#include <asm/ptrace.h>



#ifdef CONFIG_ISA_ARCOMPACT



/* These DPFP regs need to be saved/restored across ctx-sw */

struct arc_fpu {

	struct {
@@ -18,11 +20,35 @@ struct arc_fpu { 
	} aux_dpfp[2];

};



extern void fpu_save_restore(struct task_struct *p, struct task_struct *n);

#define fpu_init_task(regs)



#else



/*

 * ARCv2 FPU Control aux register

 *   - bits to enable Traps on Exceptions

 *   - Rounding mode

 *

 * ARCv2 FPU Status aux register

 *   - FPU exceptions flags (Inv, Div-by-Zero, overflow, underflow, inexact)

 *   - Flag Write Enable to clear flags explicitly (vs. by fpu instructions

 *     only

 */



struct arc_fpu {

	unsigned int ctrl, status;

};



extern void fpu_init_task(struct pt_regs *regs);



#endif	/* !CONFIG_ISA_ARCOMPACT */



extern void fpu_save_restore(struct task_struct *p, struct task_struct *n);



#else	/* !CONFIG_ARC_FPU_SAVE_RESTORE */



#define fpu_save_restore(p, n)

#define fpu_init_task(regs)



#endif	/* CONFIG_ARC_FPU_SAVE_RESTORE */

arch/arc/kernel/Makefile

+2 −0
Original line number Diff line number Diff line
@@ -23,7 +23,9 @@ obj-$(CONFIG_PERF_EVENTS) += perf_event.o 
obj-$(CONFIG_JUMP_LABEL)		+= jump_label.o



obj-$(CONFIG_ARC_FPU_SAVE_RESTORE)	+= fpu.o

ifdef CONFIG_ISA_ARCOMPACT

CFLAGS_fpu.o   += -mdpfp

endif



ifdef CONFIG_ARC_DW2_UNWIND

CFLAGS_ctx_sw.o += -fno-omit-frame-pointer

arch/arc/kernel/fpu.c

+27 −0
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
#include <linux/sched.h>

#include <asm/fpu.h>



#ifdef CONFIG_ISA_ARCOMPACT



/*

 * To save/restore FPU regs, simplest scheme would use LR/SR insns.

 * However since SR serializes the pipeline, an alternate "hack" can be used
@@ -50,3 +52,28 @@ void fpu_save_restore(struct task_struct *prev, struct task_struct *next) 
		: "r" (zero), "r" (*(readfrom + 3)), "r" (*(readfrom + 2))

	);

}



#else



void fpu_init_task(struct pt_regs *regs)

{

	/* default rounding mode */

	write_aux_reg(ARC_REG_FPU_CTRL, 0x100);



	/* set "Write enable" to allow explicit write to exception flags */

	write_aux_reg(ARC_REG_FPU_STATUS, 0x80000000);

}



void fpu_save_restore(struct task_struct *prev, struct task_struct *next)

{

	struct arc_fpu *save = &prev->thread.fpu;

	struct arc_fpu *restore = &next->thread.fpu;



	save->ctrl = read_aux_reg(ARC_REG_FPU_CTRL);

	save->status = read_aux_reg(ARC_REG_FPU_STATUS);



	write_aux_reg(ARC_REG_FPU_CTRL, restore->ctrl);

	write_aux_reg(ARC_REG_FPU_STATUS, restore->status);

}



#endif