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Subject: Re: [PATCH] riscv: set default pm_power_off to NULL
To:     Dimitri John Ledkov <dimitri.ledkov@canonical.com>,
        linux-riscv@lists.infradead.org
Cc:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, linux-kernel@vger.kernel.org
References: <20210907002847.111633-1-dimitri.ledkov@canonical.com>
From:   Ron Economos <w6rz@comcast.net>
Message-ID: <31e42fe2-0a9b-6d2d-33fe-be66d516b9cf@comcast.net>
Date:   Wed, 8 Sep 2021 22:11:16 -0700
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On 9/6/21 5:28 PM, Dimitri John Ledkov 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>
> ---
>   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();
>   }

Works good here. Tested on HiFive Unmatched, Ubuntu 21.04 and kernel 5.14.2

Tested-by: Ron Economos <w6rz@comcast.net>