From: Marc Zyngier <marc.zyngier@arm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Brendan Higgins <brendanhiggins@google.com>,
wsa@the-dreams.de, robh+dt@kernel.org, mark.rutland@arm.com,
tglx@linutronix.de, jason@lakedaemon.net, joel@jms.id.au,
vz@mleia.com, mouse@mayc.ru, clg@kaod.org
Cc: linux-i2c@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, openbmc@lists.ozlabs.org
Subject: Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for Aspeed
Date: Tue, 28 Mar 2017 10:40:38 +0100 [thread overview]
Message-ID: <91936f1a-0a0d-4091-b981-976503a6f7cd@arm.com> (raw)
In-Reply-To: <1490692375.3177.119.camel@kernel.crashing.org>
On 28/03/17 10:12, Benjamin Herrenschmidt wrote:
> On Tue, 2017-03-28 at 09:32 +0100, Marc Zyngier wrote:
>> I'm a bit concerned by this. It means that you can't even mask an
>> interrupt. Is that really what you intend to do? Or all that the HW can
>> do? If you cannot mask an interrupt, you're at the mercy of a screaming
>> device...
>
> This is not really an interrupt controller. It's a "summary" register
> that reflects the state of the 14 i2c controller interrupts.
>
> This approach does have the advantage of providing separate counters in
> /proc/interrupts which is rather nice, but it does have overhead. On
> those shittly little ARMv9 400Mhz cores it can be significant.
<pedantic>
s/ARMv9/ARM9/, as we're still on variations of the ARMv8 architecture ;-)
</pedantic>
A 400MHz ARM9 (which is either ARMv4 or ARMv5) is not too bad (hey, we
still have a couple of Versatile-ABs here...). Caches are pretty small
though.
> I would personally have some kind of trick to register a single
> interrupt handler that calls directly the handlers of the respective
> i2c busses via a simple indirection for speed, maybe adding my custom
> sysfs or debugfs statistics. But that's just me trying to suck the last
> cycle out of the bloody thing ;-)
I'd hope the irqdomain itself to be pretty light (the revmap should help
here), but of course you're going to do more work. Counters also come at
a cost. It'd be interesting to see if Brendan has any overhead data
about this.
Cheers,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2017-03-28 9:41 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-28 5:12 [PATCH v6 0/5] i2c: aspeed: added driver for Aspeed I2C Brendan Higgins
2017-03-28 5:12 ` [PATCH v6 1/5] irqchip/aspeed-i2c-ic: binding docs for Aspeed I2C Interrupt Controller Brendan Higgins
2017-03-28 8:49 ` Benjamin Herrenschmidt
2017-03-29 10:34 ` Brendan Higgins
2017-03-29 12:11 ` Benjamin Herrenschmidt
2017-03-29 20:51 ` Brendan Higgins
2017-03-29 21:17 ` Benjamin Herrenschmidt
2017-04-03 14:16 ` Rob Herring
2017-03-28 5:12 ` [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for Aspeed Brendan Higgins
2017-03-28 8:32 ` Marc Zyngier
2017-03-28 9:12 ` Benjamin Herrenschmidt
2017-03-28 9:40 ` Marc Zyngier [this message]
2017-03-28 20:50 ` Benjamin Herrenschmidt
2017-03-29 9:59 ` Brendan Higgins
2017-03-29 10:55 ` Marc Zyngier
2017-03-28 8:52 ` Benjamin Herrenschmidt
2017-03-29 10:58 ` Joel Stanley
2017-03-29 20:16 ` Brendan Higgins
2017-03-28 5:12 ` [PATCH v6 3/5] i2c: aspeed: added documentation for Aspeed I2C driver Brendan Higgins
2017-03-28 8:54 ` Benjamin Herrenschmidt
2017-03-29 10:25 ` Brendan Higgins
2017-04-03 14:22 ` Rob Herring
2017-04-03 14:24 ` Rob Herring
2017-03-28 5:12 ` [PATCH v6 4/5] i2c: aspeed: added driver for Aspeed I2C Brendan Higgins
2017-03-28 8:57 ` Benjamin Herrenschmidt
2017-03-28 9:09 ` Benjamin Herrenschmidt
2017-03-29 10:23 ` Brendan Higgins
2017-03-31 0:33 ` Joel Stanley
2017-03-31 7:33 ` Benjamin Herrenschmidt
2017-04-24 18:56 ` Brendan Higgins
2017-04-25 2:19 ` Benjamin Herrenschmidt
2017-04-25 8:32 ` Brendan Higgins
2017-04-25 8:50 ` Ryan Chen
2017-04-25 9:34 ` Benjamin Herrenschmidt
2017-04-25 9:47 ` Ryan Chen
2017-04-25 19:50 ` Brendan Higgins
2017-04-26 0:52 ` Ryan Chen
2017-03-28 5:12 ` [PATCH v6 5/5] i2c: aspeed: added slave support for Aspeed I2C driver Brendan Higgins
2017-03-31 0:01 ` [PATCH v6 0/5] i2c: aspeed: added driver for Aspeed I2C Andrew Jeffery
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