linux-kernel - Re: [PATCH v2 0/8] qcom: support wakeup capable GPIOs

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Date:   Wed, 30 Jan 2019 10:03:13 -0700
From:   Lina Iyer <ilina@...eaurora.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Evan Green <evgreen@...omium.org>,
        Marc Zyngier <marc.zyngier@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        rplsssn@...eaurora.org, linux-arm-msm@...r.kernel.org,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v2 0/8] qcom: support wakeup capable GPIOs

On Mon, Jan 28 2019 at 07:19 -0700, Linus Walleij wrote:
>On Thu, Jan 24, 2019 at 9:22 PM Lina Iyer <ilina@...eaurora.org> wrote:
>
>> This is a bug fix submission of the v1 posted here [1]. The discussion on how
>> to represent the wakeup-parent interrupt controller is on-going [2] here. The
>> reiew comments in [1], from Doug and Stephen are addressed in this patch.
>>
>> The series attempts to add GPIO chip in hierarchy with PDC interrupt controller
>> that can detect and wakeup the GPIOs routed to it, when the system is
>> suspend/deep sleep mode.
>
>I kind of start to get the hang of this now. This is starting to
>look finished. Some words on the hierarchical GPIO IRQs:
>
>I have started to look into hierarchical GPIO+irqchip since
>the usage of such is spreading.
>
>I have been on to Thierry patches trying to make him implement
>more generic helpers in the gpiolib irqchip library functions.
>
>In short I see the following:
>
>- Hierarchical gpiochips all have .alloc() and .translate() functions
>  that look more or less the same.
>
Yes.

>- They all fall down to remapping either tuples or entire ranges
>  of IRQs from parent to child with a linear look-up table on
>  allocation.
>
I would think this would be the generic case, unless its QCOM, where we
would want to push the tuples up hierarchy :(

>So my idea would be to add support for this into the gpiolib
>hierarchical irqchip helper: by supplying a parent irqdomain
>and a list of translation tuples, we should be able to handle
>pretty much any hierarchical GPIO irqdomain (famous last
>words).
>
We would read the tuples from DT? Also please consider Rob's idea of
specifying hierarchy from [2].

>Right now I am converting the IXP4xx platform to hierarchical
>IRQ from the ground up (it is not even using device tree
>so it is a bit of a challenge) but it seems to be working.
>
>So I will try to post this in some hopefully working form, and
>on top of those changes or before them introduce some
>helpers in the core for hierarchical irqs. Or I fail.
>
Thanks, please copy me on the thread. I would not want to miss this.

>Anyways, I do not think my ambitions for refactoring the
>helpers can stand in the way of support for these use cases
>and new hardware, so maybe we need to merge a few
>more hierarchical drivers just bypassing the gpiolib
>helpers. I don't want to block development, and I suspect
>Thierry might be getting annoyed at me at this point, so
>we should maybe just pile up a few more hierarchical
>chips so I can refactor them later.
>
>What do you think?
>
I attempted refactoring the .alloc and .translate and for a generic case
and it seemed like it would fit the bill very well. Will await your
patches.

Thanks,
Lina