From: Marc Zyngier <maz@kernel.org>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
Dipen Patel <dipenp@nvidia.com>,
Kent Gibson <warthog618@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jon Hunter <jonathanh@nvidia.com>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
linux-tegra <linux-tegra@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Arnd Bergmann <arnd@arndb.de>,
Richard Cochran <richardcochran@gmail.com>
Subject: Re: GTE - The hardware timestamping engine
Date: Tue, 23 Mar 2021 18:21:09 +0000 [thread overview]
Message-ID: <87h7l1k9yi.wl-maz@kernel.org> (raw)
In-Reply-To: <YFm9r/tFkzVlYDEp@orome.fritz.box>
On Tue, 23 Mar 2021 10:06:39 +0000,
Thierry Reding <thierry.reding@gmail.com> wrote:
[...]
> Obviously if we don't integrate this with IRQs directly, it becomes a
> bit more difficult to relate the captured timestamps to the events
> across subsystem boundaries. I'm not sure how this would be solved
> properly. If the events are sufficiently rare, and it's certain that
> none will be missed, then it should be possible to just pull a timestamp
> from the timestamp FIFO for each event.
>
> All of that said, I wonder if perhaps hierarchical IRQ domains can
> somehow be used for this. We did something similar on Tegra not too long
> ago for wake events, which are basically IRQs exposed by a parent IRQ
> chip that allows waking up from system sleep. There are some
> similarities between that and GTE in that the wake events also map to a
> subset of GPIOs and IRQs and provide additional functionalities on top.
>
> I managed to mess up the implementation and Marc stepped in to clean
> things up, so Cc'ing him since he's clearly more familiar with the topic
> than I am.
Sure, but I'm pretty clueless when it comes to what this GTE thing
does (it has a fast car ring to it, which isn't a selling point for
me... ;-).
If, as I understand it, it is supposed to collect timestamps on
signalling of IRQs, you could make it part of the kernel's view of the
interrupt path by "pushing" a domain on top of the IRQ stack,
triggering the configuration/timestamping of this interrupt.
What is completely unclear to me is how you extract information from
it. The IRQ doesn't really give you an interface to extract a lot of
information aside from an interrupt count and what is defined as the
interrupt state. A timestamp doesn't really count as state, so you'd
need to invent something new here.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
next prev parent reply other threads:[~2021-03-23 18:22 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 22:33 GTE - The hardware timestamping engine Dipen Patel
2021-03-20 11:56 ` Linus Walleij
2021-03-20 12:44 ` Arnd Bergmann
2021-03-20 15:38 ` Richard Cochran
2021-03-22 20:33 ` Dipen Patel
2021-03-23 9:03 ` Thierry Reding
2021-03-23 12:51 ` Richard Cochran
2021-03-22 6:00 ` Kent Gibson
2021-03-22 20:21 ` Dipen Patel
2021-03-23 0:32 ` Kent Gibson
2021-03-23 1:53 ` Dipen Patel
2021-03-23 2:59 ` Kent Gibson
2021-03-23 4:09 ` Dipen Patel
2021-03-23 5:22 ` Kent Gibson
2021-03-23 9:08 ` Linus Walleij
2021-03-23 10:06 ` Thierry Reding
2021-03-23 18:21 ` Marc Zyngier [this message]
2021-03-23 18:25 ` Dipen Patel
2021-03-23 21:19 ` Dipen Patel
2021-03-23 18:01 ` Dipen Patel
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