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

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Date:   Wed, 8 Aug 2018 07:26:32 +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 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.

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).

Thanks,

	M.
-- 
Without deviation from the norm, progress is not possible.