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Date: Sat, 23 Mar 2019 10:42:58 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Stephen Boyd <swboyd@...omium.org> cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-gpio@...r.kernel.org, Lina Iyer <ilina@...eaurora.org>, Marc Zyngier <marc.zyngier@....com> Subject: Re: [PATCH] genirq: Respect IRQCHIP_SKIP_SET_WAKE in irq_chip_set_wake_parent() Stephen, On Fri, 22 Mar 2019, Stephen Boyd wrote: > Quoting Thomas Gleixner (2019-03-21 02:26:26) > > > > set_irq_wake_real() returns 0 when the topmost chip has SKIP_SET_WAKE set. > > Just to confirm, the topmost chip would be chip B or chip C below? Yes. A is the parent of B, resp. the grandparent of C > > > > So let's assume we have the following chains: > > > > chip A -> chip B > > > > chip A -> chip B -> chip C > > > > chip A has SKIP_SET_WAKE not set > > chip B has SKIP_SET_WAKE set > > chip C has SKIP_SET_WAKE not set and invokes irq_chip_set_wake_parent() > > > > Now assume we have interrupt X connected to chip B and interrupt Y > > connected to chip C. > > > > If irq_set_wake() is called for interrupt X, then the function returns > > without trying to invoke the set_wake() callback of chip A. > > It's not clear to me that having SKIP_SET_WAKE set means "completely > ignore set wake for irqs from this domain" vs. "skip setting wake here > because the .irq_set_wake() is intentionally omitted for this chip". That's a really good question, but I'd say that if one part of the hierarchy does not require set wake, then this means no further action required. > Reading Santosh's reasoning in commit 60f96b41f71d ("genirq: Add > IRQCHIP_SKIP_SET_WAKE flag") just further confuses me because it sounds > like the latter. That preceeds hierarchical irq domains. So back then a hierarchy was expressed by weird callbacks, hardcoded dependencies, etc. That means if the top level chip had SKIP_SET_WAKE set, the whole hierarchy was excluded. > > If irq_set_wake() is called for interrupt Y, irq_chip_set_wake_parent() is > > invoked from chip C which then skips chip B, but tries to invoke the > > callback on chip A. > > > > That's inconsistent and changes the existing behaviour. So IMO, the right > > thing to do is to return 0 from irq_chip_set_wake_parent() when the parent > > has SKIP_SET_WAKE set and not to try to follow the whole chain. That should > > fix your problem nicely w/o changing behaviour. > > Ok. I understand that with hierarchical chips you want it to be explicit > in the code that a parent chip needs to be called or not. This works for I think so. > me, and it's actually how I had originally solved this problem. Will you > merge your patch or do you want me to resend it with some updated commit > text? Please send a new version. Thanks, tglx
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