From: Miroslav Lichvar <mlichvar@redhat.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: "Csókás, Bence" <csokas.bence@prolan.hu>,
linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org,
"Szentendrei, Tamás" <szentendrei.tamas@prolan.hu>,
"Alexandre Belloni" <alexandre.belloni@bootlin.com>
Subject: Re: [RFC PATCH v2] rtc: pcf2127: Add PPS capability through Seconds Interrupt
Date: Wed, 12 Jun 2024 09:50:26 +0200 [thread overview]
Message-ID: <ZmlTQsgRiW9fmYcB@localhost> (raw)
In-Reply-To: <Zmks31shpsnoLQ3k@hoboy.vegasvil.org>
On Tue, Jun 11, 2024 at 10:06:39PM -0700, Richard Cochran wrote:
> On Tue, Jun 11, 2024 at 05:04:57PM +0200, Csókás, Bence wrote:
>
> > PCF2127/29/31 is capable of generating an interrupt on every
> > second (SI) or minute (MI) change. It signals this through
> > the Minute/Second Flag (MSF) as well, which needs to be cleared.
>
> This is a RFC, and my comment is that a PPS from an RTC is not useful
> to the Linux kernel.
I think a TCXO-based RTC can be useful to user space to improve
holdover performance with NTP/PTP. There already is the RTC_UIE_ON
ioctl to enable interrupts and receive them in user space.
The advantage of the PPS device over the ioctl would be more accurate
timestamping (kernel vs user-space). Should PPS be supported, it would
be nice if it worked generally with all drivers that support RTC_UIE_ON.
--
Miroslav Lichvar
next prev parent reply other threads:[~2024-06-12 7:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-06-11 15:04 [RFC PATCH v2] rtc: pcf2127: Add PPS capability through Seconds Interrupt Csókás, Bence
2024-06-12 5:06 ` Richard Cochran
2024-06-12 7:50 ` Miroslav Lichvar [this message]
2024-06-12 9:16 ` Csókás Bence
2024-06-12 11:01 ` Alexandre Belloni
2024-06-13 3:25 ` Richard Cochran
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