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From:   Anup Patel <anup@brainfault.org>
Date:   Tue, 7 Sep 2021 09:06:27 +0530
Message-ID: <CAAhSdy0E5x3e4mkYtL0gk6be2hZEF8KbSTP4DpWCkH_ce3AvYg@mail.gmail.com>
Subject: Re: [PATCH] riscv: set default pm_power_off to NULL
To:     Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Cc:     linux-riscv <linux-riscv@lists.infradead.org>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        "linux-kernel@vger.kernel.org List" <linux-kernel@vger.kernel.org>
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On Tue, Sep 7, 2021 at 5:59 AM Dimitri John Ledkov
<dimitri.ledkov@canonical.com> wrote:
>
> Set pm_power_off to NULL like on all other architectures, check if it
> is set in machine_halt() and machine_power_off() and fallback to
> default_power_off if no other power driver got registered.
>
> This brings riscv architecture inline with all other architectures,
> and allows to reuse exiting power drivers unmodified.
>
> Kernels without legacy SBI v0.1 extensions (CONFIG_RISCV_SBI_V01 is
> not set), do not set pm_power_off to sbi_shutdown(). There is no
> support for SBI v0.3 system reset extension either. This prevents
> using gpio_poweroff on SiFive HiFive Unmatched.
>
> Tested on SiFive HiFive unmatched, with a dtb specifying gpio-poweroff
> node and kernel complied without CONFIG_RISCV_SBI_V01.
>
> BugLink: https://bugs.launchpad.net/bugs/1942806
> Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>

Looks good to me.

Reviewed-by: Anup Patel <anup@brainfault.org>

BTW, SBI v0.3 system reset patch can be merged any day
because SBI v0.3 spec is already released.

Regards,
Anup

> ---
>  arch/riscv/kernel/reset.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/reset.c b/arch/riscv/kernel/reset.c
> index ee5878d968..9c842c4168 100644
> --- a/arch/riscv/kernel/reset.c
> +++ b/arch/riscv/kernel/reset.c
> @@ -12,7 +12,7 @@ static void default_power_off(void)
>                 wait_for_interrupt();
>  }
>
> -void (*pm_power_off)(void) = default_power_off;
> +void (*pm_power_off)(void) = NULL;
>  EXPORT_SYMBOL(pm_power_off);
>
>  void machine_restart(char *cmd)
> @@ -23,10 +23,16 @@ void machine_restart(char *cmd)
>
>  void machine_halt(void)
>  {
> -       pm_power_off();
> +       if (pm_power_off != NULL)
> +               pm_power_off();
> +       else
> +               default_power_off();
>  }
>
>  void machine_power_off(void)
>  {
> -       pm_power_off();
> +       if (pm_power_off != NULL)
> +               pm_power_off();
> +       else
> +               default_power_off();
>  }
> --
> 2.30.2
>