[RFC PATCH 1/1] lib: sbi_timer: Added a blocking wait function that waits until a certain condition is true or timeout occurs

[Xiang W]

在 2022-06-29星期三的 14:42 +0100，Adnan Rahman Chowdhury写道：
> Motivation: Suppose a peripheral needs to be configured to transmit data.
> There is an SFR bit which indicates that the peripheral is ready to transmit.
> The firmware should check the bit and will only transmit data when the
> peripheral is ready. When the firmware starts polling the SFR, the peripheral
> could be busy transmitting/receiving other data so the firmware must wait
> till that completes. Assuming that there is no other way, the
> firmware shouldn't wait indefinitely.
> 
> The function sbi_timer_waitms_until() will constantly check whether a certain
> condition is met, or timeout occurs. It can be used for the cases when a
> timeout is required.
> 
> Signed-off-by: Adnan Rahman Chowdhury <adnan.chowdhury at sifive.com>
LGTM

Reviewed-by: Xiang W <wxjstz at 126.com>
> ---
>  include/sbi/sbi_timer.h |  3 +++
>  lib/sbi/sbi_timer.c     | 18 ++++++++++++++++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/include/sbi/sbi_timer.h b/include/sbi/sbi_timer.h
> index 63ef1af..ea3dbdd 100644
> --- a/include/sbi/sbi_timer.h
> +++ b/include/sbi/sbi_timer.h
> @@ -48,6 +48,9 @@ static inline void sbi_timer_udelay(ulong usecs)
>         sbi_timer_delay_loop(usecs, 1000000, NULL, NULL);
>  }
>  
> +bool sbi_timer_waitms_until(bool (*predicate)(void *), void *arg,
> +                           uint64_t timeout_ms);
> +
>  /** Get timer value for current HART */
>  u64 sbi_timer_value(void);
>  
> diff --git a/lib/sbi/sbi_timer.c b/lib/sbi/sbi_timer.c
> index acdba92..d93036d 100644
> --- a/lib/sbi/sbi_timer.c
> +++ b/lib/sbi/sbi_timer.c
> @@ -81,6 +81,24 @@ void sbi_timer_delay_loop(ulong units, u64 unit_freq,
>                 delay_fn(opaque);
>  }
>  
> +bool sbi_timer_waitms_until(bool(*predicate)(void*), void* arg,
> +                           uint64_t timeout_ms)
> +{
> +       bool ret = true;
> +       uint64_t start_time = sbi_timer_value();
> +       uint64_t ticks =
> +               (sbi_timer_get_device()->timer_freq / 1000) *
> +               (timeout_ms);
> +       do {
> +               if (predicate(arg))
> +                       break;
> +               if (sbi_timer_value() - start_time  >= ticks)
> +                       ret = false;
> +       } while(ret);
> +
> +       return ret;
> +}
> +
>  u64 sbi_timer_value(void)
>  {
>         if (get_time_val)
> -- 
> 2.30.2
> 
>