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Date:   Mon, 27 Mar 2023 15:22:51 +0200
From:   Andrew Jones <ajones@ventanamicro.com>
To:     Sia Jee Heng <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@starfivetech.com,
        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
Message-ID: <20230327132251.dejgmcpxjdrqzmvk@orel>
References: <20230323045604.536099-1-jeeheng.sia@starfivetech.com>
 <20230323045604.536099-5-jeeheng.sia@starfivetech.com>
 <20230327131025.6bawvoti65sth4rk@orel>
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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
        select EDAC_SUPPORT
        select GENERIC_ARCH_TOPOLOGY
        select GENERIC_ATOMIC64 if !64BIT


Thanks,
drew