linux-kernel - Re: [PATCH v4 3/3] pinctrl: Add Xilinx ZynqMP pinctrl driver support

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Date:   Thu, 25 Mar 2021 09:57:23 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Sai Krishna Potthuri <lakshmis@...inx.com>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Michal Simek <michals@...inx.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        git <git@...inx.com>,
        "saikrishna12468@...il.com" <saikrishna12468@...il.com>
Subject: Re: [PATCH v4 3/3] pinctrl: Add Xilinx ZynqMP pinctrl driver support

On Mon, Mar 22, 2021 at 4:25 PM Sai Krishna Potthuri
<lakshmis@...inx.com> wrote:
> [Andy]

> > > > > +       PIN_CONFIG_IOSTANDARD = PIN_CONFIG_END + 1, };
> > > >
> > > > I'm lost here. What is IO standard exactly? Why it can't be in
> > > > generic headers?
> > > It represents LVCMOS 3.3 volts/ LVCMOS 1.8 volts.
> > > Since this is specific to Xilinx ZynqMP platform, considered to be
> > > added in the driver file.
> >
> > So, why can't we create a couple of bits to represent this voltages in the
> > generic header and gain usability for others as well?
>
> I see some drivers are maintaining the configuration list in the driver file, if
> the configuration is specific to the driver.
>
> We can move this to generic header if it is used by others as well.
> Ok, will wait for Linus to comment.
> >
> > Linus?

While it is fine to add custom pin config options to pin controllers
for hopelessly idiomatic stuff, this does look like it should be
using PIN_CONFIG_POWER_SOURCE with the voltage rail
as parameter, see
include/linux/pinctrl/pinconf-generic.h

If you're not using that then tell us why.

Yours,
Linus Walleij