Re: [PATCH v2 2/3] ARM: lib32: pbl: implement get_time_ns and is_timeout

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

On 8/11/26 12:13 PM, Stefan Kerkmann wrote:
> ARMv7-A cores can implement the optional 64bit wide generic timer
> CNTPCT[1]. If it is present we can use it to implement the get_time_ns
> and is_timeout helpers which in turn enable the whole read_poll_timeout
> class of functions in the PBL. As it is guaranteed that the timer won't
> wrap for 40 years no overflow handling is necessary.
> 
> [1]: See "ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition
> (rev C.d)", Chapter B8 "The Generic Timer"
> 
> Signed-off-by: Stefan Kerkmann <s.kerkmann@pengutronix.de>
> ---
>  arch/arm/lib32/arm_architected_timer.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm/lib32/arm_architected_timer.c b/arch/arm/lib32/arm_architected_timer.c
> index 54eca13f8b..75f74cbc15 100644
> --- a/arch/arm/lib32/arm_architected_timer.c
> +++ b/arch/arm/lib32/arm_architected_timer.c
> @@ -10,8 +10,21 @@ void arm_architected_timer_udelay(unsigned long us)
>  	unsigned long long ticks, cntfrq = get_cntfrq();
>  	unsigned long long start = get_cntpct();
>  
> -	ticks = DIV_ROUND_DOWN_ULL((us * cntfrq), 1000000);
> +	ticks = DIV_ROUND_DOWN_ULL((us * cntfrq), MSECOND);
>  
>  	while ((long)(start + ticks - get_cntpct()) > 0)
>  		;
>  }
> +
> +uint64_t get_time_ns(void)
> +{
> +	return get_cntpct() * SECOND / get_cntfrq();

I think you need to use one of the 64-bit division macros here.

> +int is_timeout(uint64_t start, uint64_t time_offset_ns)
> +{
> +	if ((int64_t)(start + time_offset_ns - get_time_ns()) < 0)
> +		return 1;
> +	else
> +		return 0;

That's a convoluted way to write

  return get_time_ns() >= start + time_offset_ns;

Why did you structure it this way with the cast?

(A 64-bit nanosecond timestamp overflows after hundreds of years).

Cheers,
Ahmad

> +}
> 

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