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: 8+ 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
2024-06-12 6:23 ` kernel test robot
2024-06-12 10:47 ` kernel test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ZmlTQsgRiW9fmYcB@localhost \
--to=mlichvar@redhat.com \
--cc=alexandre.belloni@bootlin.com \
--cc=csokas.bence@prolan.hu \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-rtc@vger.kernel.org \
--cc=richardcochran@gmail.com \
--cc=szentendrei.tamas@prolan.hu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.