[PATCH v2 1/1] lib: sbi_timer: Added a blocking wait function that waits until a certain condition is satisfied or timeout occurs

[Anup Patel]

On Thu, Jun 30, 2022 at 3:16 PM Adnan Rahman Chowdhury
<adnan.chowdhury at sifive.com> wrote:
>
> 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 satisfied, 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>
> Reviewed-by: Xiang W <wxjstz at 126.com>

Looks good to me.

Reviewed-by: Anup Patel <anup at brainfault.org>

Regards,
Anup

> ---
>  include/sbi/sbi_timer.h | 18 ++++++++++++++++++
>  lib/sbi/sbi_timer.c     | 13 +++++++++++++
>  2 files changed, 31 insertions(+)
>
> diff --git a/include/sbi/sbi_timer.h b/include/sbi/sbi_timer.h
> index 63ef1af..ac48e2b 100644
> --- a/include/sbi/sbi_timer.h
> +++ b/include/sbi/sbi_timer.h
> @@ -48,6 +48,24 @@ static inline void sbi_timer_udelay(ulong usecs)
>         sbi_timer_delay_loop(usecs, 1000000, NULL, NULL);
>  }
>
> +/**
> + * A blocking function that will wait until @p predicate returns true or
> + * @p timeout_ms milliseconds elapsed. @p arg will be passed as argument to
> + * @p predicate function.
> + *
> + * @param predicate Pointer to a function that returns true if certain
> + * condition is met. It shouldn't block the code execution.
> + * @param arg Argument to pass to @p predicate.
> + * @param timeout_ms Timeout value in milliseconds. The function will return
> + * false if @p timeout_ms time period elapsed but still @p predicate doesn't
> + * return true.
> + *
> + * @return true if @p predicate returns true within @p timeout_ms, false
> + * otherwise.
> + */
> +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..649a4e6 100644
> --- a/lib/sbi/sbi_timer.c
> +++ b/lib/sbi/sbi_timer.c
> @@ -81,6 +81,19 @@ 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)
> +{
> +       uint64_t start_time = sbi_timer_value();
> +       uint64_t ticks =
> +               (sbi_timer_get_device()->timer_freq / 1000) *
> +               timeout_ms;
> +       while(!predicate(arg))
> +               if (sbi_timer_value() - start_time  >= ticks)
> +                       return false;
> +       return true;
> +}
> +
>  u64 sbi_timer_value(void)
>  {
>         if (get_time_val)
> --
> 2.30.2
>
>
> --
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