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Subject: Re: [PATCH] synchronize_irq needs a barrier
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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> >  - even when you ignore the interrupt (because the driver doesn't care, 
> >    it's suspending), you need to make sure the hardware gets shut up by 
> >    reading (or writing) the proper interrupt status register.
> I agree, but while device is powered off, its registers can't be accessed
> Thus, if I ack the IRQ every time the handler is called, I will access the 
> powered off device (this is probably won't hurt a lot, but a bit incorrectly)

It will actually crash your machine on some platforms. So no, best is to
-not- ack. The masking is enough, the IRQ will go down eventually.

Ben.