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

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Date:   Mon, 28 Jan 2019 15:17:22 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Lina Iyer <ilina@...eaurora.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 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.

- 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.

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).

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.

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?

Yours,
Linus Walleij