From: Thomas Gleixner <tglx@linutronix.de>
To: Biju Das <biju.das.jz@bp.renesas.com>,
William Breathitt Gray <william.gray@linaro.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
Rob Herring <robh@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Philipp Zabel <p.zabel@pengutronix.de>,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Magnus Damm <magnus.damm@gmail.com>,
"linux-renesas-soc@vger.kernel.org"
<linux-renesas-soc@vger.kernel.org>,
"linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>,
"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@bp.renesas.com>,
Fabrizio Castro <fabrizio.castro.jz@renesas.com>
Subject: RE: [PATCH 0/6] Add RZ/V2M Compare-Match Timer (TIM) support
Date: Sat, 10 Dec 2022 11:59:12 +0100 [thread overview]
Message-ID: <875yejcynz.ffs@tglx> (raw)
In-Reply-To: <OS0PR01MB5922293733EFD0D4F3E6B270861F9@OS0PR01MB5922.jpnprd01.prod.outlook.com>
On Sat, Dec 10 2022 at 07:52, Biju Das wrote:
> scheduling tick is 4millisec. so if we want callback at 1 microsec,
> then we need to use clock_nanosleep. Getting 1 microsec callback to
> user space is challenging as the scheduling tick is only 4 millisec.
The tick is only relevant if high resolution timers are disabled because
then hrtimers are expired in the tick. If high resolution timers are
enabled then the hrtimer expiry happens at the exact expiry time.
What's challenging about the 1 microsecond accuracy is that the system
immanent latencies are already in that range. So while the timer fires
exactly, the actual execution of the woken up task in user space is not
exact as that is subject to the worst case sum of latencies in the
system.
Thanks,
tglx
next prev parent reply other threads:[~2022-12-10 10:59 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-05 14:59 [PATCH 0/6] Add RZ/V2M Compare-Match Timer (TIM) support Biju Das
2022-12-05 14:59 ` [PATCH 2/6] dt-bindings: timer: Add RZ/V2M TIM binding Biju Das
2022-12-05 14:59 ` [PATCH 4/6] dt-bindings: counter: Add RZ/V2M TIM counter binding Biju Das
2022-12-05 14:59 ` [PATCH 6/6] arm64: dts: renesas: r9a09g011: Add tim nodes Biju Das
2022-12-05 22:50 ` [PATCH 0/6] Add RZ/V2M Compare-Match Timer (TIM) support Rob Herring
2022-12-06 8:13 ` Biju Das
2022-12-06 8:40 ` Geert Uytterhoeven
2022-12-06 8:57 ` Thomas Gleixner
2022-12-06 9:45 ` Biju Das
2022-12-07 7:52 ` Biju Das
2022-12-07 10:53 ` Thomas Gleixner
2022-12-07 11:35 ` Biju Das
2022-12-07 16:49 ` Thomas Gleixner
2022-12-09 22:24 ` William Breathitt Gray
2022-12-10 7:52 ` Biju Das
2022-12-10 10:59 ` Thomas Gleixner [this message]
2022-12-06 8:59 ` Biju Das
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=875yejcynz.ffs@tglx \
--to=tglx@linutronix.de \
--cc=biju.das.jz@bp.renesas.com \
--cc=daniel.lezcano@linaro.org \
--cc=devicetree@vger.kernel.org \
--cc=fabrizio.castro.jz@renesas.com \
--cc=geert+renesas@glider.be \
--cc=geert@linux-m68k.org \
--cc=krzysztof.kozlowski+dt@linaro.org \
--cc=linux-clk@vger.kernel.org \
--cc=linux-iio@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=magnus.damm@gmail.com \
--cc=mturquette@baylibre.com \
--cc=p.zabel@pengutronix.de \
--cc=prabhakar.mahadev-lad.rj@bp.renesas.com \
--cc=robh@kernel.org \
--cc=sboyd@kernel.org \
--cc=william.gray@linaro.org \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).