linux-kernel - Re: [PATCH v2 2/2] pinctrl: add NXP S32 SoC family support

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Message-ID: <CAGETcx8V0xop2E11oL3CcaOe4E7w61-suHXU4A-V7AdhRxrUQA@mail.gmail.com>
Date:   Wed, 14 Dec 2022 15:08:25 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Chester Lin <clin@...e.com>, Fabio Estevam <festevam@...il.com>,
        Dong Aisheng <aisheng.dong@....com>,
        Shawn Guo <shawnguo@...nel.org>, Jacky Bai <ping.bai@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>, s32@....com,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Larisa Grigore <larisa.grigore@....com>,
        Ghennadi Procopciuc <Ghennadi.Procopciuc@....com>,
        Andrei Stefanescu <andrei.stefanescu@....com>,
        Radu Pirea <radu-nicolae.pirea@....com>,
        Andreas Färber <afaerber@...e.de>,
        Matthias Brugger <mbrugger@...e.com>,
        Matthew Nunez <matthew.nunez@....com>,
        Phu Luu An <phu.luuan@....com>,
        Stefan-Gabriel Mirea <stefan-gabriel.mirea@....com>
Subject: Re: [PATCH v2 2/2] pinctrl: add NXP S32 SoC family support

On Fri, Dec 9, 2022 at 3:26 AM Linus Walleij <linus.walleij@...aro.org> wrote:
>
> On Fri, Dec 9, 2022 at 5:39 AM Chester Lin <clin@...e.com> wrote:
> >
> > Hi Linus and Fabio,
> >
> > Thanks for your time to review this patch!
> >
> > On Thu, Dec 08, 2022 at 10:37:36PM +0100, Linus Walleij wrote:
> > > On Thu, Dec 8, 2022 at 12:04 AM Fabio Estevam <festevam@...il.com> wrote:
> > >
> > > > In other imx8m pinctrl drivers we pass:
> > > (...)
> > > > > +module_platform_driver(s32g_pinctrl_driver);
> > > >
> > > > And we also register it in arch_initcall() level.
> > >
> > > Do you really need that though? This driver certainly does not.
> > >
> > > I was under the impression that recent changes to the probe-order
> > > logic has made most explicit arch_ etc initcall orderings surplus.
> > >
> >
> > Could bool/tristate options in the Kconfig be the key point?
> >
> > Based on current design I prefer to build the s32g2 pinctrl driver as built-in
> > rather than a loadable module. IIUC, when the driver is not built as module
> > then the initcall ordering should still matter.
>
> It is true that if you compile something into a module then all initicalls
> are the same: they are called when the module is loaded.
>
> But the remaining initcalls used to be assigned to core, arch, subsystem
> etc in order for resources (such as clocks, regulators or pins) to be
> available before the drivers that need them get probed.
>
> However there was first deferred probe to partially solve the problem
> and recently a large and refined series that use the dependencies in
> the device tree to resolve probe order.
>
> Saravana Kannan has been working tirelessly at this, issueing
> git log --oneline --author="Saravana Kannan"
> you will see the scope of this work.
>

Thanks Linus.

For a system using DT, fw_devlink's goal is to make module load
ordering or driver registration ordering irrelevant to proper
functioning of the kernel/drivers. It should automatically figure out
the dependencies and have the devices probe in the right order. It's
already true for at least 80% of the cases for a system using DT.
There are some known issues I'm either working on or have on my To do
list. So, if you see a case where fw_devlink is not handling it
correctly, please let me know.

-Saravana