linux-kernel - Re: [PATCH] [RFC PATCH v1] clocksource: entend the max_delta_ns of timer-riscv andtimer-clint to ULONG_MAX

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Date:   Tue, 8 Aug 2023 11:30:22 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Vincent Chen <vincent.chen@...ive.com>
Cc:     daniel.lezcano@...aro.org, tglx@...utronix.de, palmer@...belt.com,
        paul.walmsley@...ive.com, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFC PATCH v1] clocksource: entend the max_delta_ns of
 timer-riscv andtimer-clint to ULONG_MAX

Hey Vincent,

On Tue, Aug 08, 2023 at 12:51:45PM +0800, Vincent Chen wrote:
> From: Vincentc Chen <vincent.chen@...ive.com>
> 
> When registering the riscv-timer or clint-timer as a clock_event device,
> the driver needs to specify the value of max_delta_ticks. This value
> directly influences the max_delta_ns, which signifies the maximum time
> interval for configuring subsequent clock events. Currently, both
> riscv-timer and clint-timer are set with a max_delta_ticks value of
> 0x7fff_ffff. When the timer operates at a high frequency, such as 1GHz,
> this causes the system only can sleep for a short time. For the 1GHz
> case, the sleep cannot exceed two seconds. To address this limitation,
> refer to other timer implementations to extend it to 2^(bit-width of the
> timer) - 1. Because the bit-width of $mtimecmp is 64bit, so this value
> becomes ULONG_MAX (0xffff_ffff_ffff_ffff).

You've marked this as RFC - what is it that you are unsure about that
prevents this from being a regular patch?

Thanks,
Conor.

> 
> Signed-off-by: Vincentc Chen <vincent.chen@...ive.com>
> ---
>  drivers/clocksource/timer-clint.c | 2 +-
>  drivers/clocksource/timer-riscv.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clocksource/timer-clint.c b/drivers/clocksource/timer-clint.c
> index 9a55e733ae99..09fd292eb83d 100644
> --- a/drivers/clocksource/timer-clint.c
> +++ b/drivers/clocksource/timer-clint.c
> @@ -131,7 +131,7 @@ static int clint_timer_starting_cpu(unsigned int cpu)
>  	struct clock_event_device *ce = per_cpu_ptr(&clint_clock_event, cpu);
>  
>  	ce->cpumask = cpumask_of(cpu);
> -	clockevents_config_and_register(ce, clint_timer_freq, 100, 0x7fffffff);
> +	clockevents_config_and_register(ce, clint_timer_freq, 100, ULONG_MAX);
>  
>  	enable_percpu_irq(clint_timer_irq,
>  			  irq_get_trigger_type(clint_timer_irq));
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index da3071b387eb..b25c91d41968 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -94,7 +94,7 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
>  	ce->irq = riscv_clock_event_irq;
>  	if (riscv_timer_cannot_wake_cpu)
>  		ce->features |= CLOCK_EVT_FEAT_C3STOP;
> -	clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
> +	clockevents_config_and_register(ce, riscv_timebase, 100, ULONG_MAX);
>  
>  	enable_percpu_irq(riscv_clock_event_irq,
>  			  irq_get_trigger_type(riscv_clock_event_irq));
> -- 
> 2.34.1
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

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