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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Wed, 1 Jul 2020 11:53:25 +0200
Message-ID: <CAK8P3a1E_UecNq=7rvceQoXdFkmnBFOyUtxrpJ1bF6cLWOtNqQ@mail.gmail.com>
Subject: Re: [PATCH V3 02/10] init.h: Fix the __setup_param() macro for module build
To:     Anson Huang <anson.huang@nxp.com>
Cc:     Russell King - ARM Linux <linux@armlinux.org.uk>,
        Shawn Guo <shawnguo@kernel.org>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Sascha Hauer <kernel@pengutronix.de>,
        Fabio Estevam <festevam@gmail.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "oleksandr.suvorov@toradex.com" <oleksandr.suvorov@toradex.com>,
        Stefan Agner <stefan.agner@toradex.com>,
        Peng Fan <peng.fan@nxp.com>, Abel Vesa <abel.vesa@nxp.com>,
        Aisheng Dong <aisheng.dong@nxp.com>,
        Andy Duan <fugang.duan@nxp.com>,
        Daniel Baluta <daniel.baluta@nxp.com>,
        YueHaibing <yuehaibing@huawei.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        linux-clk <linux-clk@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
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On Wed, Jul 1, 2020 at 11:27 AM Anson Huang <anson.huang@nxp.com> wrote:
> > Subject: Re: [PATCH V3 02/10] init.h: Fix the __setup_param() macro for
> > module build
> >
> > On Wed, Jul 1, 2020 at 7:14 AM Anson Huang <anson.huang@nxp.com>
> > wrote:
> >
> > I don't understand what your plan is here. Do you mean you will leave that
> > part of the clk driver as built-in?
>
> I meant I will leave the #else block of __setup_param() defined as nothing as below to
> make module build passed.
>
> #define __setup_param(str, unique_id, fn, early)        /* nothing */

No, I think that is  mistake. It will mean that other drivers with the same
bug as the imx-clk driver will appear to build fine, but not work correctly.

A build error is better than silently dropping the command line parsing in
my opinion.

> > This error just means you can't have a __setup_param() call in a loadable
> > module, which we already knew. If you need to do something with the clocks
> > early on, that has to be in built-in code and cannot be in a module. If you don't
> > need that code, then you should just remove it from both the modular version
> > and the built-in version.
> >
> > What is the purpose of that __setup_param() argument parsing in the clock
> > driver?
>
> We need the code for proper uart clock management of earlycon, from the code, it
> is trying to keep console uart clock enabled during kernel boot up.

Why not move this all to a separate file then and only build it when
CONFIG_CLK_IMX=y?
It seems that you don't need the imx_keep_uart_clocks_param() if the
clk driver is
loaded as a module, but then you also don't need the imx_clk_disable_uart()
and imx_register_uart_clocks() functions or the associated variables.

     Arnd