[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 Wed, Jul 6, 2022 at 8:53 AM Anup Patel <anup at brainfault.org> wrote:
>
> 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>

I have shortened the patch subject at time of merging this patch.

Applied this patch to the riscv/opensbi repo

Thanks,
Anup

>
> 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
> >
> >
> > --
> > opensbi mailing list
> > opensbi at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/opensbi