Date:   Fri, 15 Sep 2017 08:09:57 -0700
From:   Thierry Reding <thierry.reding@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Jonathan Hunter <jonathanh@...dia.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        ext Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH 00/16] gpio: Tight IRQ chip integration and banked
 infrastructure

On Thu, Sep 14, 2017 at 03:54:56PM +0200, Linus Walleij wrote:
> On Fri, Sep 1, 2017 at 8:57 PM, Thierry Reding <thierry.reding@...il.com> wrote:
> 
> > here's the latest series of patches that implement the tighter IRQ chip
> > integration as well as the banked GPIO infrastructure that we had
> > discussed a couple of weeks/months back.
> 
> Yes it has become really tasty now, don't you think :)
> 
> I really like the series.
> 
> Banks are handled in the core, exactly as I wanted.
> 
> I will likely go in and change some things I don't like, like switching
> num_pins in the bank to num_lines. I have preferred that terminology
> to avoid confusion with pin control. So GPIO chips have lines, not pins.
> But it's so minor that I can fix it up if you don't want to.

I rebased this on today's linux-next and noticed that there was a small
conflict. I can rebase and work in the changes that you requested.

I'm travelling this week and next, so it may take until after -rc2 that
I can send out a new version that's properly build-tested.

> We also need to go in and patch Documentation/gpio/driver.txt
> to represent the current best practice. But that can be later,
> separate patch.
> 
> > The first couple of patches are mostly preparatory work in order to
> > consolidate all IRQ chip related fields in a new structure and create
> > the base functionality for adding IRQ chips.
> >
> > After that, I've added the Tegra186 GPIO support patch that makes use of
> > the new tight integration.
> >
> > To round things off the new banked GPIO infrastructure is added (along
> > with some more preparatory work), followed by the conversion of the two
> > Tegra GPIO drivers to the new infrastructure.
> 
> I have put all on a branch for pushing to the test builders to begin with.
> 
> Then I plan to make one branch with all infrastructure patches
> (patches 1-10, 12-14) and pull that into devel, then apply patch
> 11 and 15-16 directly on devel.
> 
> That way other subsystems (pinctrl ...) can pull in the infrastructure
> for people adding new gpiochips this cycle.

Sounds good.

> > Any thoughts on this? I'd like to target 4.15 with this,
> 
> Me, too.
> 
> > unless you'd be
> > willing to take this into 4.14, which I doubt at this point. The absence
> > of a GPIO driver has been hampering Tegra186 support upstream for a
> > while now, so it'd be good to make progress on this.
> 
> Sorry about that. Let's move ahead with this now, it is neat and
> clean.
> 
> What I want (as maintainer) is a bit of fingerpointing at the drivers
> that need to be converted to use the new banking infrastructure
> so they don't stay with their old crappy design pattern. OMAP is
> a clear candidate right? (Added Tony to CC...)

OMAP should be able to use this infrastructure, but it may not want to
because the semantics would change slightly. Currently OMAP registers a
GPIO chip for each bank, whereas this infrastructure exposes multiple
banks via a single chip.

There might be some userspace that relies on the existence of multiple
chips, but Tony can probably knows that better than I.

> Who else?

gpio-intel-mid.c and gpio-merrifield.c look like they could use this new
infrastructure. So do gpio-pca953x.c, gpio-stmpe.c and gpio-tc3589x.c.

gpio-ws16c48.c is another one that uses a similar pattern.

Thierry

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