Re: [PATCH] synchronize_irq needs a barrier

quoted

 - 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.