linux-kernel - Re: [PATCH v5 01/10] pinctrl: generic: Add bi-directional and output-enable

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Message-ID: <20170609075028.GE15739@w540>
Date:   Fri, 9 Jun 2017 09:50:28 +0200
From:   jmondi <jacopo@...ndi.org>
To:     Dong Aisheng <dongas86@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Chris Brandt <Chris.Brandt@...esas.com>,
        Jacopo Mondi <jacopo+renesas@...ndi.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 01/10] pinctrl: generic: Add bi-directional and
 output-enable

Hi Dong,

On Fri, Jun 09, 2017 at 03:26:57PM +0800, Dong Aisheng wrote:
> Hi Linus & j,
>
> >>
> >> I just want to know if "output-enable" is the right name?
> >> "output-buffer-enable"?
> >
> > Great! Thanks!
> >
> > On naming: if we need "output-buffer-enable" should we add
> > "input-buffer-enable" as well?
> >
> > Currently we are using "input-enable" to pair with "output-enable",
> > but as you said, just "output-enable" when "output-high" and
> > "output-low" are there already seems a bit confusing.
> > At the same time "input-buffer-enable" seems to actually be just
> > electrically equivalent to "input-enable", so adding it is a bit of a
> > waste as well.
> >
> > I see three options here:
> >
> > 1) Add "output-buffer-enable" and "input-buffer-enable"
> > we end up with
> > "output-high"
> > "output-low"
> > "input-enable"
> > "output-buffer-enable"
> > "input-buffer-enable"
> >
> > 2) Add "output-buffer-enable" only
> > we end up with
> > "output-high"
> > "output-low"
> > "input-enable"
> > "output-buffer-enable"
> >
> > Binding may be confusing as in one case we use "output-buffer-enable"
> > while in the other "input-enable"
> >
> > 3) Add "output-enable" only
> > "output-high"
> > "output-low"
> > "input-enable"
> > "output-enable"
> >
> > As you, I don't like "output-enable" that much but it pairs better with
> > "input-enable".
> >
> > I'll let you and DT people decide on this, as it's really an ABI definition
> > problem and you have better judgment there.
> >
>
> What's the final decision of this?

I admit a was buying a bit of time and post-poned the gentle ping for
any final word on this. But since you're asking I'll second your
question :)

>
> I saw the following revert patch in pinctrl-next but did not see a successive
> patch to add output-enable back?
>

Still waiting to have a feedback on which properties to add, that's
why I have not sent anything yet.

Thanks
   j

> IMX7ULP pinctrl driver is pending on this because it needs use both
> input-enable and output-enable if we want to make them generic property.
>
> commit b4d2ea2af95cb77e2f320e24da526280d4aa2f6b
> Author: Linus Walleij <linus.walleij@...aro.org>
> Date:   Mon May 8 10:48:21 2017 +0200
>
>     Revert "pinctrl: generic: Add bi-directional and output-enable"
>
>     This reverts commit 8c58f1a7a4b6d1d723bf25fef9d842d5a11200d0.
>
>     It turns out that applying these generic properties was
>     premature: the properties used in the driver using this
>     are of unclear electrical nature and the subject need to
>     be discussed.
>
>     Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
>
> Regards
> Dong Aisheng
>
> >>
> >> > I see commit 42d5a11200d0[1] has not been reverted yet as Andy asked
> >> > in some previous email.
> >>
> >> I'm just overloaded. I sent that revert to Torvalds today.
> >
> > Thank you. Didn't want to put pressure ;)
> >>
> >> > I can send another version of that patch with
> >> > only 'output-enable' if you wish.
> >>
> >> That's what we want.
> >>
> >> > Once we reach consesus, I can then send v6 of our pin controller driver
> >> > based on that.
> >>
> >> OK sounds like a plan.
> >>
> >> Sorry for the mess, I'm just trying to get this right :/
> >
> > Not a mess, and thanks for your effort in maintaining  all of this
> >
> > Thanks
> >    j
> >>
> >> Yours,
> >> Linus Walleij