linux-kernel - Re: [PATCH v1 4/6] pps: generators: Add PPS Generator TIO Driver

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Message-ID: <87y1g05014.ffs@tglx>
Date:   Wed, 18 Oct 2023 00:58:31 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     lakshmi.sowjanya.d@...el.com, jstultz@...gle.com,
        giometti@...eenne.com, corbet@....net, linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, linux-doc@...r.kernel.org,
        andriy.shevchenko@...ux.intel.com, eddie.dong@...el.com,
        christopher.s.hall@...el.com, pandith.n@...el.com,
        mallikarjunappa.sangannavar@...el.com, thejesh.reddy.t.r@...el.com,
        lakshmi.sowjanya.d@...el.com,
        Peter Hilber <peter.hilber@...nsynergy.com>
Subject: Re: [PATCH v1 4/6] pps: generators: Add PPS Generator TIO Driver

On Tue, Oct 17 2023 at 18:27, Thomas Gleixner wrote:
> static bool pps_arm_next_pulse(struct pps_tio *tio, ktime_t expires)
> {
> 	u64 art;
>
> 	if (!ktime_real_to_base_clock(expires, CSID_X86_ART, &art))
>         	return false;
>
> 	pps_compv_write(tio, art - ART_HW_DELAY_CYCLES);
>         return true;
> }
>
> ktime_real_to_base_clock() does not exist, but that's the function you
> really want to have.

It just occured to me that CLOCK_REALTIME might not really the best
clock to base this on.

It's obvious why this can't be based on CLOCK_MONOTONIC, but I rather
would base this on CLOCK_TAI which at least does not have the issue of
leap seconds and the related nightmares.

Thanks,

        tglx