linux-kernel - Re: [PATCH v3 3/4] LoongArch: Save and restore PERCPU_BASE

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Date: Fri, 12 Apr 2024 12:18:46 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Thomas Gleixner <tglx@...utronix.de>, Arnd Bergmann <arnd@...db.de>, Marc Zyngier <maz@...nel.org>, 
	loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v3 3/4] LoongArch: Save and restore PERCPU_BASE_KS for
 ACPI S3 state

Hi, Tiezhu,

On Thu, Apr 11, 2024 at 9:05 AM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> Currently, per_cpu_offset(x) is defined as __per_cpu_offset[x])
> only under CONFIG_SMP in include/asm-generic/percpu.h, that is
> to say, the implementation of loongarch_common_resume() which
> calls per_cpu_offset(0) is not suitable for the case of non-SMP,
> so do not write per_cpu_offset(0) to PERCPU_BASE_KS when resume,
> just save the value of PERCPU_BASE_KS when suspend and restore
> it when resume to make it work well for both SMP and non-SMP.
For non-SMP you need PERCPU_BASE_KS to do what?

Huacai

>
> Tested with the command "rtcwake -d rtc1 -s 20 -m mem -v", dmesg
> shows that "PM: suspend entry (deep)" and "PM: suspend exit".
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
>  arch/loongarch/power/suspend.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/power/suspend.c b/arch/loongarch/power/suspend.c
> index 166d9e06a64b..7a97949ddade 100644
> --- a/arch/loongarch/power/suspend.c
> +++ b/arch/loongarch/power/suspend.c
> @@ -16,6 +16,7 @@
>  #include <asm/tlbflush.h>
>
>  u64 loongarch_suspend_addr;
> +static u64 saved_pcpu_base;
>
>  struct saved_registers {
>         u32 ecfg;
> @@ -36,6 +37,7 @@ void loongarch_common_suspend(void)
>         saved_regs.pwctl1 = csr_read32(LOONGARCH_CSR_PWCTL1);
>         saved_regs.ecfg = csr_read32(LOONGARCH_CSR_ECFG);
>         saved_regs.euen = csr_read32(LOONGARCH_CSR_EUEN);
> +       saved_pcpu_base = csr_read64(PERCPU_BASE_KS);
>
>         loongarch_suspend_addr = loongson_sysconf.suspend_addr;
>  }
> @@ -44,7 +46,7 @@ void loongarch_common_resume(void)
>  {
>         sync_counter();
>         local_flush_tlb_all();
> -       csr_write64(per_cpu_offset(0), PERCPU_BASE_KS);
> +       csr_write64(saved_pcpu_base, PERCPU_BASE_KS);
>         csr_write64(eentry, LOONGARCH_CSR_EENTRY);
>         csr_write64(eentry, LOONGARCH_CSR_MERRENTRY);
>         csr_write64(tlbrentry, LOONGARCH_CSR_TLBRENTRY);
> --
> 2.42.0
>
>