From: Mason <slash.tmp@free.fr>
To: Marc Zyngier <marc.zyngier@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jason Cooper <jason@lakedaemon.net>
Cc: Mark Rutland <mark.rutland@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Design of interrupt controller driver
Date: Sat, 3 Jun 2017 20:20:33 +0200 [thread overview]
Message-ID: <6f8f3b96-ba86-51a8-1789-4c7d75c92079@free.fr> (raw)
In-Reply-To: <8bce8bdd-5801-f0c3-ada3-e1c68acc8913@free.fr>
On 03/06/2017 18:49, Mason wrote:
> 1) The interrupt router has 128 inputs and 24 outputs.
> Therefore, several devices have to share an output line.
> I believe they *must* be of the same interrupt type?
> In the limit, we could use
> - 1 output line for level high
> - 1 output line for level low
> - 1 output line for edge rising
> - 1 output line for edge falling
> Is that correct?
>
> 2) Assume a device that signals an interrupt by pulsing
> its interrupt line, i.e. the signal rises and then falls
> a few cycles later. Assume we have grouped several such
> devices on a single output line. When an interrupt triggers,
> I see no way to determine which device requested attention
> from the processor.
> Does this mean that edge interrupts cannot be grouped
> on a single output line for such a controller?
A year ago, maz wrote:
> OK, so this is definitely a pure router, and the lack of latch makes
> it completely unsuitable for a a cascaded interrupt controller. At
> least, we've managed to establish that this thing will never be able
> to handle more than 24 devices in a sane way. So let's forget about
> Mason's idea of cascading everything to a single output line, and
> let's focus on your initial idea of having something similar to TI's
> crossbar, which is a much saner approach.
Then later added:
> Unless you limit your mux [to] level interrupts only, I cannot see how
> you could deal with cascaded interrupts. By the time you receive an
> edge, the line will have dropped, and you won't be able to identify
> the source interrupt.
To recap:
Sharing level interrupts would be OK.
Sharing "pulse" (rapid high/low) interrupts is impossible.
Sharing the DMA interrupts should be OK.
AFAIK, there are no devices using "pulses" in the system.
Will carefully re-read the July patch RFC.
Regards.
next prev parent reply other threads:[~2017-06-03 18:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-03 16:49 Design of interrupt controller driver Mason
2017-06-03 18:20 ` Mason [this message]
2017-06-04 13:55 ` Thomas Gleixner
2017-06-04 17:18 ` Mason
2017-06-04 20:13 ` Thomas Gleixner
2017-06-04 23:40 ` Mason
2017-06-05 8:23 ` Thomas Gleixner
2017-06-05 11:57 ` Mason
2017-06-06 7:39 ` Thomas Gleixner
2017-06-06 9:35 ` Mason
2017-06-06 10:29 ` Thomas Gleixner
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=6f8f3b96-ba86-51a8-1789-4c7d75c92079@free.fr \
--to=slash.tmp@free.fr \
--cc=arnd@arndb.de \
--cc=jason@lakedaemon.net \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=marc.zyngier@arm.com \
--cc=mark.rutland@arm.com \
--cc=tglx@linutronix.de \
/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).