RE: [PATCH v7 4/4] RISC-V: Add arch functions to support hibernation/suspend-to-disk

[JeeHeng Sia <jeeheng.sia@starfivetech.com>]

> -----Original Message-----
> From: Andrew Jones <ajones@ventanamicro.com>
> Sent: Monday, March 27, 2023 9:23 PM
> To: JeeHeng Sia <jeeheng.sia@starfivetech.com>
> Cc: paul.walmsley@sifive.com; palmer@dabbelt.com; aou@eecs.berkeley.edu; linux-riscv@lists.infradead.org; linux-
> kernel@vger.kernel.org; Leyfoon Tan <leyfoon.tan@starfivetech.com>; Mason Huo <mason.huo@starfivetech.com>; Conor Dooley
> <conor.dooley@microchip.com>
> Subject: Re: [PATCH v7 4/4] RISC-V: Add arch functions to support hibernation/suspend-to-disk
> 
> On Mon, Mar 27, 2023 at 03:10:25PM +0200, Andrew Jones wrote:
> > On Thu, Mar 23, 2023 at 12:56:04PM +0800, Sia Jee Heng wrote:
> > > Low level Arch functions were created to support hibernation.
> > > swsusp_arch_suspend() relies code from __cpu_suspend_enter() to write
> > > cpu state onto the stack, then calling swsusp_save() to save the memory
> > > image.
> > >
> > > Arch specific hibernation header is implemented and is utilized by the
> > > arch_hibernation_header_restore() and arch_hibernation_header_save()
> > > functions. The arch specific hibernation header consists of satp, hartid,
> > > and the cpu_resume address. The kernel built version is also need to be
> > > saved into the hibernation image header to making sure only the same
> > > kernel is restore when resume.
> > >
> > > swsusp_arch_resume() creates a temporary page table that covering only
> > > the linear map. It copies the restore code to a 'safe' page, then start
> > > to restore the memory image. Once completed, it restores the original
> > > kernel's page table. It then calls into __hibernate_cpu_resume()
> > > to restore the CPU context. Finally, it follows the normal hibernation
> > > path back to the hibernation core.
> > >
> > > To enable hibernation/suspend to disk into RISCV, the below config
> > > need to be enabled:
> > > - CONFIG_ARCH_HIBERNATION_HEADER
> > > - CONFIG_ARCH_HIBERNATION_POSSIBLE
> > >
> > > Signed-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
> > > Reviewed-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
> > > Reviewed-by: Mason Huo <mason.huo@starfivetech.com>
> > > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > > ---
> > >  arch/riscv/Kconfig                 |   6 +
> > >  arch/riscv/include/asm/assembler.h |  20 ++
> > >  arch/riscv/include/asm/suspend.h   |  19 ++
> > >  arch/riscv/kernel/Makefile         |   1 +
> > >  arch/riscv/kernel/asm-offsets.c    |   5 +
> > >  arch/riscv/kernel/hibernate-asm.S  |  77 ++++++
> > >  arch/riscv/kernel/hibernate.c      | 427 +++++++++++++++++++++++++++++
> > >  7 files changed, 555 insertions(+)
> > >  create mode 100644 arch/riscv/kernel/hibernate-asm.S
> > >  create mode 100644 arch/riscv/kernel/hibernate.c
> > >
> >
> > Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
> 
> Actually, I forgot to point out something. As hibernation depends on
> suspend.c for save/restore_csrs, we need something like
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 73cca7f17f6f..f1d2289df660 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -54,7 +54,7 @@ config RISCV
>         select CLINT_TIMER if !MMU
>         select CLONE_BACKWARDS
>         select COMMON_CLK
> -       select CPU_PM if CPU_IDLE
> +       select CPU_PM if CPU_IDLE || HIBERNATION
Sure. Will add it
>         select EDAC_SUPPORT
>         select GENERIC_ARCH_TOPOLOGY
>         select GENERIC_ATOMIC64 if !64BIT
> 
> 
> Thanks,
> drew

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