linux-kernel - Re: [PATCH v2 1/5] drivers: pinctrl: qcom: add wakeup capability to GPIO

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Date:   Mon, 27 Aug 2018 20:20:34 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Lina Iyer <ilina@...eaurora.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Stephen Boyd <sboyd@...nel.org>, evgreen@...omium.org,
        rplsssn@...eaurora.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-msm@...r.kernel.org,
        Rajendra Nayak <rnayak@...eaurora.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Andy Gross <andy.gross@...aro.org>,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v2 1/5] drivers: pinctrl: qcom: add wakeup capability to
 GPIO

On Mon 27 Aug 18:46 PDT 2018, Lina Iyer wrote:
> On Mon, Aug 27 2018 at 18:26 -0600, Bjorn Andersson wrote:
> > On Mon 27 Aug 09:56 PDT 2018, Lina Iyer wrote:
[..]
> > > Thanks, I will look into Hans's RFCv2. But what would help me would be
> > > to avoid creating the IRQ for the GPIO itself (I have the latent IRQ),
> > > if I could just return that instead in gpio_to_irq(), it might be
> > > easier. I understand ->to_irq() is supposed to be a translate function
> > > only, I can avoid the dance of enabling and diabling the PDC IRQ on
> > > suspend and resume.
> > > 
> > 
> > I did implement gpio_to_irq() like this in the PMIC gpio/mpp drivers and
> > we've since concluded that we need to move this to some hierarchical
> > interrupt controller, because people like Linus expect to be able to say
> > 
> >  interrupts = <&gpio_controller 1 IRQ_TYPE_EDGE_RISING>
> > 
> > which is something used all over the place with the TLMM driver today.
> 
> Does it have to be &gpio_controller, can it be another interrupt controller?
> 
> Say,
> 	interrupts-extended = <&pdc 1 IRQ_TYPE_EDGE_RISING>;
> 

It would require that the GPIO interrupt number space of the PDC matches
the pin numbering of the TLMM, to be somewhat maintainable.

And it would still require DT-writers to know that if the implementation
of a compatible, that references a TLMM IRQ, wants to mark the IRQ wake
capable it needs to reference the PDC instead...while still having a
pinmux/pinconf setting for the TLMM.

And for gpio_to_irq() we would need to do the mapping that you suggest,
so the TLMM still needs to have all these references to the PDC.


So I think it would be nice if we could avoid this scenario, but I don't
have any good ideas of how to do this right now...

Regards,
Bjorn