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Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for Aspeed

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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.

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 ;-)

Cheers,
Ben.

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[PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for Aspeed Brendan Higgins <brendanhiggins@google.com> - 2017-03-28 07:20 +0200
  Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for  Aspeed Marc Zyngier <marc.zyngier@arm.com> - 2017-03-28 10:40 +0200
    Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for  Aspeed Marc Zyngier <marc.zyngier@arm.com> - 2017-03-28 11:50 +0200
      Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller  for Aspeed Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-03-29 00:10 +0200
        Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for Aspeed Brendan Higgins <brendanhiggins@google.com> - 2017-03-29 12:10 +0200
          Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for  Aspeed Marc Zyngier <marc.zyngier@arm.com> - 2017-03-29 13:00 +0200
    Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller  for Aspeed Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-03-28 13:10 +0200
  Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller  for Aspeed Benjamin Herrenschmidt <benh@kernel.crashing.org> - 2017-03-28 11:00 +0200
  Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for Aspeed Joel Stanley <joel@jms.id.au> - 2017-03-29 13:10 +0200
    Re: [PATCH v6 2/5] irqchip/aspeed-i2c-ic: Add I2C IRQ controller for Aspeed Brendan Higgins <brendanhiggins@google.com> - 2017-03-29 22:20 +0200

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