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Commit 3d5e8012 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

ARCv2: entry: save Accumulator register pair (r58:59) if present 



Accumulator is present in configs with FPU and/or DSP MPY (mpy > 6)

Instead of doing this in pt_regs (and thus every kernel entry/exit),
this could have been done in context switch (and for user task only) as
currently kernel doesn't clobber these registers for its own accord.
However we will soon start using 64-bit multiply instructions for kernel
which can clobber these. Also gcc folks also plan to start using these
as GPRs, hence better to always save/restore them

Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent 6492f09e

arch/arc/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -406,6 +406,14 @@ config ARC_HAS_DIV_REM 
	bool "Insn: div, divu, rem, remu"

	default y



config ARC_HAS_ACCL_REGS

	bool "Reg Pair ACCL:ACCH (FPU and/or MPY > 6)"

	default n

	help

	  Depending on the configuration, CPU can contain accumulator reg-pair

	  (also referred to as r58:r59). These can also be used by gcc as GPR so

	  kernel needs to save/restore per process



endif	# ISA_ARCV2



endmenu   # "ARC CPU Configuration"

arch/arc/include/asm/entry-arcv2.h

+10 −0
Original line number Diff line number Diff line
@@ -16,6 +16,11 @@ 
	;

	; Now manually save: r12, sp, fp, gp, r25



#ifdef CONFIG_ARC_HAS_ACCL_REGS

	PUSH	r59

	PUSH	r58

#endif



	PUSH	r30

	PUSH	r12
@@ -75,6 +80,11 @@ 
	POP	r12

	POP	r30



#ifdef CONFIG_ARC_HAS_ACCL_REGS

	POP	r58

	POP	r59

#endif



.endm



/*------------------------------------------------------------------------*/

arch/arc/include/asm/ptrace.h

+4 −0
Original line number Diff line number Diff line
@@ -86,6 +86,10 @@ struct pt_regs { 


	unsigned long r12, r30;



#ifdef CONFIG_ARC_HAS_ACCL_REGS

	unsigned long r58, r59;	/* ACCL/ACCH used by FPU / DSP MPY */

#endif



	/*------- Below list auto saved by h/w -----------*/

	unsigned long r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11;

arch/arc/kernel/setup.c

+21 −9
Original line number Diff line number Diff line
@@ -319,7 +319,8 @@ static char *arc_extn_mumbojumbo(int cpu_id, char *buf, int len) 
static void arc_chk_core_config(void)

{

	struct cpuinfo_arc *cpu = &cpuinfo_arc700[smp_processor_id()];

	int fpu_enabled;

	int saved = 0, present = 0;

	char *opt_nm = NULL;;



	if (!cpu->extn.timer0)

		panic("Timer0 is not present!\n");
@@ -346,17 +347,28 @@ static void arc_chk_core_config(void) 


	/*

	 * FP hardware/software config sanity

	 * -If hardware contains DPFP, kernel needs to save/restore FPU state

	 * -If hardware present, kernel needs to save/restore FPU state

	 * -If not, it will crash trying to save/restore the non-existant regs

	 *

	 * (only DPDP checked since SP has no arch visible regs)

	 */

	fpu_enabled = IS_ENABLED(CONFIG_ARC_FPU_SAVE_RESTORE);



	if (cpu->extn.fpu_dp && !fpu_enabled)

		pr_warn("CONFIG_ARC_FPU_SAVE_RESTORE needed for working apps\n");

	else if (!cpu->extn.fpu_dp && fpu_enabled)

		panic("FPU non-existent, disable CONFIG_ARC_FPU_SAVE_RESTORE\n");

	if (is_isa_arcompact()) {

		opt_nm = "CONFIG_ARC_FPU_SAVE_RESTORE";

		saved = IS_ENABLED(CONFIG_ARC_FPU_SAVE_RESTORE);



		/* only DPDP checked since SP has no arch visible regs */

		present = cpu->extn.fpu_dp;

	} else {

		opt_nm = "CONFIG_ARC_HAS_ACCL_REGS";

		saved = IS_ENABLED(CONFIG_ARC_HAS_ACCL_REGS);



		/* Accumulator Low:High pair (r58:59) present if DSP MPY or FPU */

		present = cpu->extn_mpy.dsp | cpu->extn.fpu_sp | cpu->extn.fpu_dp;

	}



	if (present && !saved)

		pr_warn("Enable %s for working apps\n", opt_nm);

	else if (!present && saved)

		panic("Disable %s, hardware NOT present\n", opt_nm);

}



/*