linux-kernel - Re: [PATCH RESEND RFC 1/4] drivers: pinctrl: qcom: add wakeup capability to GPIO

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Message-ID: <86wosypsvr.wl-marc.zyngier@arm.com>
Date:   Fri, 10 Aug 2018 08:45:12 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Lina Iyer <ilina@...eaurora.org>, evgreen@...omium.org,
        linus.walleij@...aro.org, bjorn.andersson@...aro.org,
        rplsssn@...eaurora.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, rnayak@...eaurora.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH RESEND RFC 1/4] drivers: pinctrl: qcom: add wakeup capability to GPIO

On Thu, 09 Aug 2018 18:30:53 +0100,
Stephen Boyd <swboyd@...omium.org> wrote:
> 
> Quoting Marc Zyngier (2018-08-07 23:26:32)
> > On Tue, 07 Aug 2018 23:05:07 -0700
> > Stephen Boyd <swboyd@...omium.org> wrote:
> > 
> > > Quoting Lina Iyer (2018-08-02 05:58:27)
> > > > On Thu, Aug 02 2018 at 01:27 -0600, Marc Zyngier wrote:  
> > > > >
> > > > >Sure. But once woken up (GIC *and* TLMM), the gpio line (which I
> > > > >assume is level) is still high at the TLMM input. So why isn't it
> > > > >registering that state once it has been woken up?
> > > > >
> > > > >I can understand that it would be missing an edge. But that doesn't
> > > > >hold for level signalling.
> > > > >  
> > > > Sure, yes. Sorry for not registering your point in my response.
> > > > Once woken up we should see the level interrupt in TLMM.  
> > > 
> > > And the level type gpio interrupt will trigger the TLMM summary
> > > interrupt line after the wakeup? So then the only thing that needs to be
> > > replayed is edge interrupts? How are edge interrupts going to be
> > > replayed?
> > 
> > Level interrupts should be taken care of without doing anything, by the
> > very nature of being a level signal.
> 
> Right. I suspect we'll still need to configure the PDC to actually wake
> up on the level triggered signal though so PDC needs to be told to
> unmask the line.

Surely this can be done at suspend time with the PDC driver tracking
the interrupts that are configured as a wake-up source (although it
needs to track an interrupt that is logically connected to the TLMM,
which sucks).

> > Edge interrupts should be replayed using check_irq_resend() after
> > taking the right locks and making the interrupt pending. Or, if there
> > is a way for SW to make the interrupt pending at the TLMM level, to use
> > that as a way to reinject the interrupt (which would be the preferred
> > way, as it avoids all kind of ugly locking considerations).
> > 
> 
> Ok. Looking at the hardware it seems that I can write the interrupt
> status bit directly for an edge type interrupt and that causes the
> interrupt handler to run. So that's good news, we can use that ability
> to directly inject interrupts here.

That's pretty good news. It means that if TLMM implements the
irq_set_irqchip_state() API, there isn't muc that needs doing, and
most of the original ugliness can go. At least I hope.

	M.

-- 
Jazz is not dead, it just smell funny.