On Fri, 25 Jul 2014, Rafael J. Wysocki wrote: > On Thursday, July 24, 2014 11:26:20 PM Peter Zijlstra wrote: > > Subject: irq: Rework IRQF_NO_SUSPENDED > > From: Peter Zijlstra <pet...@infradead.org> > > Date: Thu Jul 24 22:34:50 CEST 2014 > > > > Typically when devices are suspended they're quiesced such that they > > will not generate any further interrupts. > > > > However some devices should still generate interrupts, even when > > suspended, typically used to wake the machine back up. > > > > Such logic should ideally be contained inside each driver, if it can > > generate interrupts when suspended, it knows about this and the > > interrupt handler can deal with it. > > > > Except of course for shared interrupts, when such a wakeup device is > > sharing an interrupt line with a device that does not expect > > interrupts while suspended things can go funny. > > > > This is where IRQF_NO_SUSPEND comes in, the idea is that drivers that > > have the capability to wake the machine set IRQF_NO_SUSPEND and their > > handler will still be called, even when the IRQ subsystem is formally > > suspended. Handlers without IRQF_NO_SUSPEND will not be called. > > > > This replaced the prior implementation of IRQF_NO_SUSPEND which had > > a number of fatal issues in that it didn't actually work for the > > shared case, exactly the case it should be helping. > > > > There is still enable_irq_wake()/IRQD_WAKEUP_STATE that tries to serve > > a similar purpose but is equially wrecked for shared interrupts, > > ideally this would be removed. > > Let me comment about this particular thing. > > I had a discussion with Dmitry about that and his argument was that > enable_irq_wake() should imply IRQF_NO_SUSPEND, because drivers that > set up interrupts for system wakeup should expect those interrupts to > trigger at any time, including system suspend. Hence the patch that > added the IRQD_WAKEUP_STATE check to __disable_irq(). > > However, in the face of the problem that is being addressed here I'm > not really sure that this argument is valid, because if the driver > calling enable_irq_wake() is sharing the IRQ with another one, the > other driver may not actually know that the IRQ will be a wakeup one > and still may not expect interrupts to come to it during system > suspend/resume. > > Yes, drivers using enable_irq_wake() will likely want IRQF_NO_SUSPEND to > be set for their irqactions, but that should not imply "no suspend" for > all irqactions sharing the same desc. So I guess it may be better to go > forth and use a global "interrupts suspended" state variable instead of the > IRQS_SUSPENDED flag for each desc and throw away the IRQD_WAKEUP_STATE > check from suspend_device_irqs() entirely.
How should that global state work? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/