On Wed, Apr 10 2024 at 17:18, lakshmi.sowjanya.d@xxxxxxxxx wrote:
> +static bool pps_generate_next_pulse(struct pps_tio *tio, ktime_t expires)
> +{
> + u64 art;
> +
> + if (!ktime_real_to_base_clock(expires, CSID_X86_ART, &art)) {
> + pps_tio_disable(tio);
> + return false;
> + }
> +
> + pps_compv_write(tio, art - ART_HW_DELAY_CYCLES);
> + return true;
> +}
> +
> +static enum hrtimer_restart hrtimer_callback(struct hrtimer *timer)
> +{
> + struct pps_tio *tio = container_of(timer, struct pps_tio, timer);
> + ktime_t expires, now;
> + u32 event_count;
> +
> + guard(spinlock)(&tio->lock);
> +
> + /* Check if any event is missed. If an event is missed, TIO will be disabled*/
> + event_count = pps_tio_read(tio, TIOEC);
> + if (!tio->prev_count && tio->prev_count == event_count)
> + goto err;
> + tio->prev_count = event_count;
> + expires = hrtimer_get_expires(timer);
> + now = ktime_get_real();
> +
> + if (now - expires < SAFE_TIME_NS) {
> + if (!pps_generate_next_pulse(tio, expires + SAFE_TIME_NS))
> + goto err;
> + }
If the hrtimer callback is invoked late so that now - expires is >=
SAFE_TIME_NS then this just forwards the timer and tries again.
This lacks any form of explanation why this is correct as obviously
there will be a missing pulse, no?
> + hrtimer_forward(timer, now, NSEC_PER_SEC / 2);
> + return HRTIMER_RESTART;
> +err:
> + dev_err(tio->dev, "Event missed, Disabling Timed I/O");
> + pps_tio_disable(tio);
Why does this disable it again? The failure path in
pps_generate_next_pulse() does so already, no?
> + return HRTIMER_NORESTART;
> +}
> +
Thanks,
tglx
