Re: [kvm-unit-tests PATCH v2 2/4] lib: s390x: add CPU timer functions to time.h

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Mon,  4 Jul 2022 14:13:26 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:

> Upcoming changes will make use of the CPU timer, so add a convenience
> function to set the CPU timer.
> 
> Since shifts for both CPU timer and TOD clock are the same, introduce a
> new define TIMING_S390_SHIFT_US. The respective shifts for CPU timer and
> TOD clock reference it, so the semantic difference between the two
> defines is kept.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> ---
>  lib/s390x/asm/time.h | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/s390x/asm/time.h b/lib/s390x/asm/time.h
> index 7652a151e87a..9ae364afb8a3 100644
> --- a/lib/s390x/asm/time.h
> +++ b/lib/s390x/asm/time.h
> @@ -11,9 +11,13 @@
>  #ifndef _ASMS390X_TIME_H_
>  #define _ASMS390X_TIME_H_
>  
> -#define STCK_SHIFT_US	(63 - 51)
> +#define TIMING_S390_SHIFT_US	(63 - 51)

I would call it S390_CLOCK_SHIFT_US

> +
> +#define STCK_SHIFT_US	TIMING_S390_SHIFT_US
>  #define STCK_MAX	((1UL << 52) - 1)
>  
> +#define CPU_TIMER_SHIFT_US	TIMING_S390_SHIFT_US
> +
>  static inline uint64_t get_clock_us(void)
>  {
>  	uint64_t clk;
> @@ -45,4 +49,14 @@ static inline void mdelay(unsigned long ms)
>  	udelay(ms * 1000);
>  }
>  
> +static inline void cpu_timer_set(int64_t timeout_ms)

I would call the function cpu_timer_set_ms

so that it's clear what unit goes in, and it makes things easier if in
the future someone needs a _us version

> +{
> +	int64_t timer_value = (timeout_ms * 1000) << CPU_TIMER_SHIFT_US;
> +	asm volatile (
> +		"spt %[timer_value]\n"
> +		:
> +		: [timer_value] "Q" (timer_value)
> +	);
> +}
> +
>  #endif