linux-kernel - Re: [PATCH v3 2/2] clocksource/drivers/timer-riscv: Stop stimecmp when cpu hotplug

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Message-ID: <5f7179ec-e4ce-4644-8a60-ce407a4d2f11@linaro.org>
Date: Mon, 28 Oct 2024 10:44:50 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Nick Hu <nick.hu@...ive.com>, greentime.hu@...ive.com,
 zong.li@...ive.com, "Rafael J. Wysocki" <rafael@...nel.org>,
 Pavel Machek <pavel@....cz>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
 Thomas Gleixner <tglx@...utronix.de>, Andrew Jones
 <ajones@...tanamicro.com>, Conor Dooley <conor.dooley@...rochip.com>,
 Samuel Holland <samuel.holland@...ive.com>,
 Sunil V L <sunilvl@...tanamicro.com>, linux-pm@...r.kernel.org,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc: Anup Patel <anup@...infault.org>
Subject: Re: [PATCH v3 2/2] clocksource/drivers/timer-riscv: Stop stimecmp
 when cpu hotplug

On 28/10/2024 04:39, Nick Hu wrote:
> Stop the timer when the cpu is going to be offline otherwise the
> timer interrupt may be pending while performing power-down.
> 
> Suggested-by: Anup Patel <anup@...infault.org>
> Link: https://lore.kernel.org/lkml/20240829033904.477200-3-nick.hu@sifive.com/T/#u
> Signed-off-by: Nick Hu <nick.hu@...ive.com>
> Reviewed-by: Anup Patel <anup@...infault.org>
> ---
>   drivers/clocksource/timer-riscv.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index 48ce50c5f5e6..166dee14e46b 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -127,6 +127,12 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
>   static int riscv_timer_dying_cpu(unsigned int cpu)
>   {
>   	disable_percpu_irq(riscv_clock_event_irq);
> +	/*
> +	 * Stop the timer when the cpu is going to be offline otherwise
> +	 * the timer interrupt may be pending while performing power-down.
> +	 */
> +	riscv_clock_event_stop();
> +
>   	return 0;
>   }

Should it not be the opposite?

First stop the clock which clears the interrupt and then disable the irq?

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