Re: [PATCH v10 1/8] RISC-V: Enable CPU_IDLE drivers

[Guo Ren]

Reviewed-by: Guo Ren <guoren@xxxxxxxxxx>

small questions:

On Wed, Jan 26, 2022 at 7:46 PM Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:
>
> From: Anup Patel <anup.patel@xxxxxxx>
>
> We force select CPU_PM and provide asm/cpuidle.h so that we can
> use CPU IDLE drivers for Linux RISC-V kernel.
>
> Signed-off-by: Anup Patel <anup.patel@xxxxxxx>
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxx>
> ---
>  arch/riscv/Kconfig                |  7 +++++++
>  arch/riscv/configs/defconfig      |  1 +
>  arch/riscv/configs/rv32_defconfig |  1 +
>  arch/riscv/include/asm/cpuidle.h  | 24 ++++++++++++++++++++++++
>  arch/riscv/kernel/process.c       |  3 ++-
>  5 files changed, 35 insertions(+), 1 deletion(-)
>  create mode 100644 arch/riscv/include/asm/cpuidle.h
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 5adcbd9b5e88..76976d12b463 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -46,6 +46,7 @@ config RISCV
>         select CLONE_BACKWARDS
>         select CLINT_TIMER if !MMU
>         select COMMON_CLK
> +       select CPU_PM if CPU_IDLE
>         select EDAC_SUPPORT
>         select GENERIC_ARCH_TOPOLOGY if SMP
>         select GENERIC_ATOMIC64 if !64BIT
> @@ -547,4 +548,10 @@ source "kernel/power/Kconfig"
>
>  endmenu
>
> +menu "CPU Power Management"
> +
> +source "drivers/cpuidle/Kconfig"
> +
> +endmenu
> +
>  source "arch/riscv/kvm/Kconfig"
> diff --git a/arch/riscv/configs/defconfig b/arch/riscv/configs/defconfig
> index f120fcc43d0a..a5e0482a4969 100644
> --- a/arch/riscv/configs/defconfig
> +++ b/arch/riscv/configs/defconfig
> @@ -20,6 +20,7 @@ CONFIG_SOC_SIFIVE=y
>  CONFIG_SOC_VIRT=y
>  CONFIG_SMP=y
>  CONFIG_HOTPLUG_CPU=y
> +CONFIG_CPU_IDLE=y
>  CONFIG_VIRTUALIZATION=y
>  CONFIG_KVM=m
>  CONFIG_JUMP_LABEL=y
> diff --git a/arch/riscv/configs/rv32_defconfig b/arch/riscv/configs/rv32_defconfig
> index 8b56a7f1eb06..d1b87db54d68 100644
> --- a/arch/riscv/configs/rv32_defconfig
> +++ b/arch/riscv/configs/rv32_defconfig
> @@ -20,6 +20,7 @@ CONFIG_SOC_VIRT=y
>  CONFIG_ARCH_RV32I=y
>  CONFIG_SMP=y
>  CONFIG_HOTPLUG_CPU=y
> +CONFIG_CPU_IDLE=y
>  CONFIG_VIRTUALIZATION=y
>  CONFIG_KVM=m
>  CONFIG_JUMP_LABEL=y
> diff --git a/arch/riscv/include/asm/cpuidle.h b/arch/riscv/include/asm/cpuidle.h
> new file mode 100644
> index 000000000000..71fdc607d4bc
> --- /dev/null
> +++ b/arch/riscv/include/asm/cpuidle.h
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2021 Allwinner Ltd
> + * Copyright (C) 2021 Western Digital Corporation or its affiliates.
> + */
> +
> +#ifndef _ASM_RISCV_CPUIDLE_H
> +#define _ASM_RISCV_CPUIDLE_H
> +
> +#include <asm/barrier.h>
> +#include <asm/processor.h>
> +
> +static inline void cpu_do_idle(void)
> +{
> +       /*
> +        * Add mb() here to ensure that all
> +        * IO/MEM accesses are completed prior
> +        * to entering WFI.
> +        */
> +       mb();
I think it's a separate fixup.

> +       wait_for_interrupt();
> +}
> +
> +#endif
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index 03ac3aa611f5..504b496787aa 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -23,6 +23,7 @@
>  #include <asm/string.h>
>  #include <asm/switch_to.h>
>  #include <asm/thread_info.h>
> +#include <asm/cpuidle.h>
>
>  register unsigned long gp_in_global __asm__("gp");
>
> @@ -37,7 +38,7 @@ extern asmlinkage void ret_from_kernel_thread(void);
>
>  void arch_cpu_idle(void)
>  {
maybe below is enough.
+ mb();
   wait_for_interrupt();

> -       wait_for_interrupt();
> +       cpu_do_idle();


>         raw_local_irq_enable();
>  }
>
> --
> 2.25.1
>
>
> --
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-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/