Re: [PATCH v5 2/2] pinctrl: Add driver for Sunplus SP7021

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: "Wells Lu 呂芳騰" <wells.lu@sunplus.com>
Cc: Wells Lu <wellslutw@gmail.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	devicetree <devicetree@vger.kernel.org>,
	linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
	"dvorkin@tibbo.com" <dvorkin@tibbo.com>
Subject: Re: [PATCH v5 2/2] pinctrl: Add driver for Sunplus SP7021
Date: Fri, 14 Jan 2022 11:46:04 +0200	[thread overview]
Message-ID: <CAHp75VfxtGue7bbMm_MU2GWwWo4aZLW2Pj_U9ocCQmWr6wfGMw@mail.gmail.com> (raw)
In-Reply-To: <9e15ccc8ee844f1eab320001bc8bc235@sphcmbx02.sunplus.com.tw>

On Fri, Jan 14, 2022 at 4:51 AM Wells Lu 呂芳騰 <wells.lu@sunplus.com> wrote:

...

> > > > > > > +       bool "Sunplus SP7021 PinMux and GPIO driver"
> > > > > >
> > > > > > Why bool and not tristate?
> > > > >
> > > > > Pinctrl driver is selected by many drivers in SP7021 platform.
> > > > > We never build it as a module, but build-in to kernel.
> > > > > So we use "bool".
> > > > >
> > > > > Should we set it to tristate?
> > > >
> > > > You still haven't answered "why", so I can't tell you.
> > >
> > > I am puzzled because I think I have answered "why".
> >
> > Nope. :-)
> >
> > > Because Pinctrl driver is necessary for all SP7021-based platforms.
> >
> > "Why?" Why is it necessary (to be built-in)?
>
> Pinctrl is necessary to be built-in because drivers of boot-device,
> like eMMC, SD card, NAND flash, and NOR flash drivers, need it.
>
> SP7021 supports booting from eMMC, SD card, NAND flash and NOR flash
> devices. Their drivers need Pinctrl driver probes in advance.

On x86 platforms, for example, booting from eMMC and SD card does not
require a pin control driver to be built-in. Why is this requirement
for SP platforms?

-- 
With Best Regards,
Andy Shevchenko