linux-kernel - Re: [PATCH v2] genirq: Respect IRQCHIP_SKIP_SET_WAKE in irq_chip_set_wake

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Date:   Tue, 26 Mar 2019 09:58:54 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-gpio@...r.kernel.org, Lina Iyer <ilina@...eaurora.org>
Subject: Re: [PATCH v2] genirq: Respect IRQCHIP_SKIP_SET_WAKE in irq_chip_set_wake_parent()

Quoting Marc Zyngier (2019-03-26 04:11:56)
> Hi Stephen,
> 
> On 25/03/2019 18:10, Stephen Boyd wrote:
> > This function returns an error if a child irqchip calls
> > irq_chip_set_wake_parent() but its parent irqchip has the
> > IRQCHIP_SKIP_SET_WAKE flag set. Let's return 0 for success here instead
> > because there isn't anything to do.
> > 
> > This keeps the behavior consistent with how set_irq_wake_real() is
> > implemented. That function returns 0 when the irqchip has the
> > IRQCHIP_SKIP_SET_WAKE flag set. It doesn't attempt to walk the chain of
> > parents and set irq wake on any chips that don't have the flag set
> > either. If the intent is to call the .irq_set_wake() callback of the
> > parent irqchip, then we expect irqchip implementations to omit the
> > IRQCHIP_SKIP_SET_WAKE flag and implement an .irq_set_wake() function
> > that calls irq_chip_set_wake_parent().
> > 
> > This fixes a problem on my Qualcomm sdm845 device where I can't set wake
> > on any GPIO interrupts after I apply work in progress wakeup irq patches
> > to the GPIO driver. The chain of chips looks like this:
> > 
> >  ARM GIC (skip) -> QCOM PDC (skip) -> QCOM GPIO
> 
> nit: the parenting chain is actually built the other way around (we
> don't express the 'child' relationship). This doesn't change anything to
> the patch, but would make the reasoning a but easier to understand.

I take it you want the sentence below to say 'parent' instead of 'child'
then?

> 
> > 
> > The GPIO controller is a child of the QCOM PDC irqchip which is a child
> > of the ARM GIC irqchip. The QCOM PDC irqchip has the
> > IRQCHIP_SKIP_SET_WAKE flag set, and so does the grandparent ARM GIC.
> > 
> > The GPIO driver doesn't know if the parent needs to set wake or not, so
> > it unconditionally calls irq_chip_set_wake_parent() causing this
> > function to return a failure because the parent irqchip (PDC) doesn't
> > have the .irq_set_wake() callback set. Returning 0 instead makes
> > everything work and irqs from the GPIO controller can be configured for
> > wakeup.
> > 
> > Cc: Lina Iyer <ilina@...eaurora.org>
> > Cc: Marc Zyngier <marc.zyngier@....com>
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> 
> Fixes: 08b55e2a9208e ("genirq: Add irqchip_set_wake_parent")
> Acked-by: Marc Zyngier <marc.zyngier@....com>
> 

I'm happy to resend with the commit text clarified more and the above
tags added.