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...
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From: Marc Zyngier <marc.zyngier-5wv7dgnIgG8@public.gmane.org> To: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>, Brendan Higgins <brendanhiggins-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, mark.rutland-5wv7dgnIgG8@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org, joel-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org, vz-ChpfBGZJDbMAvxtiuMwx3w@public.gmane.org, mouse-Pma6HLj0uuo@public.gmane.org, clg-Bxea+6Xhats@public.gmane.org Cc: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, openbmc-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.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-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.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... -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2017-03-28 9:41 UTC|newest] Thread overview: 57+ 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 ` 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 2017-04-03 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 5:12 ` Brendan Higgins 2017-03-28 8:32 ` Marc Zyngier 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 9:40 ` Marc Zyngier 2017-03-28 20:50 ` Benjamin Herrenschmidt 2017-03-28 20:50 ` Benjamin Herrenschmidt 2017-03-29 9:59 ` Brendan Higgins 2017-03-29 9:59 ` Brendan Higgins 2017-03-29 10:55 ` Marc Zyngier 2017-03-28 8:52 ` Benjamin Herrenschmidt 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 2017-03-28 8:54 ` Benjamin Herrenschmidt 2017-03-29 10:25 ` Brendan Higgins 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 5:12 ` 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 2017-03-31 7:33 ` Benjamin Herrenschmidt 2017-04-24 18:56 ` Brendan Higgins 2017-04-24 18:56 ` Brendan Higgins 2017-04-25 2:19 ` Benjamin Herrenschmidt 2017-04-25 8:32 ` Brendan Higgins 2017-04-25 8:32 ` 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 9:47 ` Ryan Chen 2017-04-25 19:50 ` Brendan Higgins 2017-04-26 0:52 ` Ryan Chen 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 2017-03-31 0:01 ` Andrew Jeffery 2017-03-31 0:01 ` Andrew Jeffery
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