Messages in this thread | ![/](/images/icornerl.gif) | | From | Thomas Gleixner <> | Subject | Re: [PATCH v6 09/11] pps: generators: Add PPS Generator TIO Driver | Date | Thu, 11 Apr 2024 00:28:43 +0200 |
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On Wed, Apr 10 2024 at 17:18, lakshmi.sowjanya.d@intel.com 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
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