[PATCH v4 2/4] RISC-V: Factor out common code of __cpu_resume_enter()

Sun Feb 26 18:21:56 PST 2023


> -----Original Message-----
> From: Alexandre Ghiti <alex at ghiti.fr>
> Sent: Friday, 24 February, 2023 6:19 PM
> To: JeeHeng Sia <jeeheng.sia at starfivetech.com>; paul.walmsley at sifive.com; palmer at dabbelt.com; aou at eecs.berkeley.edu
> Cc: linux-riscv at lists.infradead.org; linux-kernel at vger.kernel.org; Leyfoon Tan <leyfoon.tan at starfivetech.com>; Mason Huo
> <mason.huo at starfivetech.com>
> Subject: Re: [PATCH v4 2/4] RISC-V: Factor out common code of __cpu_resume_enter()
> 
> Hi Sia,
> 
> On 2/21/23 03:35, Sia Jee Heng wrote:
> > The cpu_resume() function is very similar for the suspend to disk and
> > suspend to ram cases. Factor out the common code into restore_csr macro
> > and restore_reg macro.
> >
> > Signed-off-by: Sia Jee Heng <jeeheng.sia at starfivetech.com>
> > ---
> >   arch/riscv/include/asm/assembler.h | 62 ++++++++++++++++++++++++++++++
> >   arch/riscv/kernel/suspend_entry.S  | 34 ++--------------
> >   2 files changed, 65 insertions(+), 31 deletions(-)
> >   create mode 100644 arch/riscv/include/asm/assembler.h
> >
> > diff --git a/arch/riscv/include/asm/assembler.h b/arch/riscv/include/asm/assembler.h
> > new file mode 100644
> > index 000000000000..727a97735493
> > --- /dev/null
> > +++ b/arch/riscv/include/asm/assembler.h
> > @@ -0,0 +1,62 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Copyright (C) 2023 StarFive Technology Co., Ltd.
> > + *
> > + * Author: Jee Heng Sia <jeeheng.sia at starfivetech.com>
> > + */
> > +
> > +#ifndef __ASSEMBLY__
> > +#error "Only include this from assembly code"
> > +#endif
> > +
> > +#ifndef __ASM_ASSEMBLER_H
> > +#define __ASM_ASSEMBLER_H
> > +
> > +#include <asm/asm.h>
> > +#include <asm/asm-offsets.h>
> > +#include <asm/csr.h>
> > +
> > +/*
> > + * restore_csr - restore hart's CSR value
> > + */
> > +	.macro restore_csr
> > +		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_EPC)(a0)
> > +		csrw	CSR_EPC, t0
> > +		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_STATUS)(a0)
> > +		csrw	CSR_STATUS, t0
> > +		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_BADADDR)(a0)
> > +		csrw	CSR_TVAL, t0
> > +		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_CAUSE)(a0)
> > +		csrw	CSR_CAUSE, t0
> > +	.endm
> > +
> > +/*
> > + * restore_reg - Restore registers (except A0 and T0-T6)
> > + */
> > +	.macro restore_reg
> > +		REG_L	ra, (SUSPEND_CONTEXT_REGS + PT_RA)(a0)
> > +		REG_L	sp, (SUSPEND_CONTEXT_REGS + PT_SP)(a0)
> > +		REG_L	gp, (SUSPEND_CONTEXT_REGS + PT_GP)(a0)
> > +		REG_L	tp, (SUSPEND_CONTEXT_REGS + PT_TP)(a0)
> > +		REG_L	s0, (SUSPEND_CONTEXT_REGS + PT_S0)(a0)
> > +		REG_L	s1, (SUSPEND_CONTEXT_REGS + PT_S1)(a0)
> > +		REG_L	a1, (SUSPEND_CONTEXT_REGS + PT_A1)(a0)
> > +		REG_L	a2, (SUSPEND_CONTEXT_REGS + PT_A2)(a0)
> > +		REG_L	a3, (SUSPEND_CONTEXT_REGS + PT_A3)(a0)
> > +		REG_L	a4, (SUSPEND_CONTEXT_REGS + PT_A4)(a0)
> > +		REG_L	a5, (SUSPEND_CONTEXT_REGS + PT_A5)(a0)
> > +		REG_L	a6, (SUSPEND_CONTEXT_REGS + PT_A6)(a0)
> > +		REG_L	a7, (SUSPEND_CONTEXT_REGS + PT_A7)(a0)
> > +		REG_L	s2, (SUSPEND_CONTEXT_REGS + PT_S2)(a0)
> > +		REG_L	s3, (SUSPEND_CONTEXT_REGS + PT_S3)(a0)
> > +		REG_L	s4, (SUSPEND_CONTEXT_REGS + PT_S4)(a0)
> > +		REG_L	s5, (SUSPEND_CONTEXT_REGS + PT_S5)(a0)
> > +		REG_L	s6, (SUSPEND_CONTEXT_REGS + PT_S6)(a0)
> > +		REG_L	s7, (SUSPEND_CONTEXT_REGS + PT_S7)(a0)
> > +		REG_L	s8, (SUSPEND_CONTEXT_REGS + PT_S8)(a0)
> > +		REG_L	s9, (SUSPEND_CONTEXT_REGS + PT_S9)(a0)
> > +		REG_L	s10, (SUSPEND_CONTEXT_REGS + PT_S10)(a0)
> > +		REG_L	s11, (SUSPEND_CONTEXT_REGS + PT_S11)(a0)
> > +	.endm
> > +
> > +#endif	/* __ASM_ASSEMBLER_H */
> 
> 
> You introduce assembler.h which in the future may contain other assembly
> functions not related to suspend: I'd rename those macros so that we
> know they are suspend related, something like
> suspend_restore_regs/suspend_restore_csrs.
Sure, these can be done.
> 
> And instead of (SUSPEND_CONTEXT_REGS + PT_XXX) you could introduce
> SUSPEND_CONTEXT_REGS_PT_XXX in asm-offsets.c?
There are already PT_XXX defined in the asm-offset.c, we should not create another set of SUSPEND_CONTEXT_REGS_PT_XXX because we can just re-use the definition instead of duplicate another set of offset which are doing the same thing. So, I would rather stick with the current definition.
	DEFINE(PT_SIZE, sizeof(struct pt_regs));
	OFFSET(PT_EPC, pt_regs, epc);
	OFFSET(PT_RA, pt_regs, ra);
	OFFSET(PT_FP, pt_regs, s0);
	OFFSET(PT_S0, pt_regs, s0);
	OFFSET(PT_S1, pt_regs, s1);
	OFFSET(PT_S2, pt_regs, s2);
> 
> 
> > diff --git a/arch/riscv/kernel/suspend_entry.S b/arch/riscv/kernel/suspend_entry.S
> > index aafcca58c19d..74a8fab8e0f6 100644
> > --- a/arch/riscv/kernel/suspend_entry.S
> > +++ b/arch/riscv/kernel/suspend_entry.S
> > @@ -7,6 +7,7 @@
> >   #include <linux/linkage.h>
> >   #include <asm/asm.h>
> >   #include <asm/asm-offsets.h>
> > +#include <asm/assembler.h>
> >   #include <asm/csr.h>
> >   #include <asm/xip_fixup.h>
> >
> > @@ -83,39 +84,10 @@ ENTRY(__cpu_resume_enter)
> >   	add	a0, a1, zero
> >
> >   	/* Restore CSRs */
> > -	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_EPC)(a0)
> > -	csrw	CSR_EPC, t0
> > -	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_STATUS)(a0)
> > -	csrw	CSR_STATUS, t0
> > -	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_BADADDR)(a0)
> > -	csrw	CSR_TVAL, t0
> > -	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_CAUSE)(a0)
> > -	csrw	CSR_CAUSE, t0
> > +	restore_csr
> >
> >   	/* Restore registers (except A0 and T0-T6) */
> > -	REG_L	ra, (SUSPEND_CONTEXT_REGS + PT_RA)(a0)
> > -	REG_L	sp, (SUSPEND_CONTEXT_REGS + PT_SP)(a0)
> > -	REG_L	gp, (SUSPEND_CONTEXT_REGS + PT_GP)(a0)
> > -	REG_L	tp, (SUSPEND_CONTEXT_REGS + PT_TP)(a0)
> > -	REG_L	s0, (SUSPEND_CONTEXT_REGS + PT_S0)(a0)
> > -	REG_L	s1, (SUSPEND_CONTEXT_REGS + PT_S1)(a0)
> > -	REG_L	a1, (SUSPEND_CONTEXT_REGS + PT_A1)(a0)
> > -	REG_L	a2, (SUSPEND_CONTEXT_REGS + PT_A2)(a0)
> > -	REG_L	a3, (SUSPEND_CONTEXT_REGS + PT_A3)(a0)
> > -	REG_L	a4, (SUSPEND_CONTEXT_REGS + PT_A4)(a0)
> > -	REG_L	a5, (SUSPEND_CONTEXT_REGS + PT_A5)(a0)
> > -	REG_L	a6, (SUSPEND_CONTEXT_REGS + PT_A6)(a0)
> > -	REG_L	a7, (SUSPEND_CONTEXT_REGS + PT_A7)(a0)
> > -	REG_L	s2, (SUSPEND_CONTEXT_REGS + PT_S2)(a0)
> > -	REG_L	s3, (SUSPEND_CONTEXT_REGS + PT_S3)(a0)
> > -	REG_L	s4, (SUSPEND_CONTEXT_REGS + PT_S4)(a0)
> > -	REG_L	s5, (SUSPEND_CONTEXT_REGS + PT_S5)(a0)
> > -	REG_L	s6, (SUSPEND_CONTEXT_REGS + PT_S6)(a0)
> > -	REG_L	s7, (SUSPEND_CONTEXT_REGS + PT_S7)(a0)
> > -	REG_L	s8, (SUSPEND_CONTEXT_REGS + PT_S8)(a0)
> > -	REG_L	s9, (SUSPEND_CONTEXT_REGS + PT_S9)(a0)
> > -	REG_L	s10, (SUSPEND_CONTEXT_REGS + PT_S10)(a0)
> > -	REG_L	s11, (SUSPEND_CONTEXT_REGS + PT_S11)(a0)
> > +	restore_reg
> >
> >   	/* Return zero value */
> >   	add	a0, zero, zero