linux-kernel - RE: [PATCH V2 3/9] clk: imx: Support building SCU clock driver as module

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Message-ID: <159296027133.62212.18074403520585879907@swboyd.mtv.corp.google.com>
Date:   Tue, 23 Jun 2020 17:57:51 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Abel Vesa <abel.vesa@....com>, Aisheng Dong <aisheng.dong@....com>,
        Andy Duan <fugang.duan@....com>,
        Anson Huang <anson.huang@....com>,
        Daniel Baluta <daniel.baluta@....com>,
        Leonard Crestez <leonard.crestez@....com>,
        Peng Fan <peng.fan@....com>,
        Stefan Agner <stefan.agner@...adex.com>, allison@...utok.net,
        arnd@...db.de, festevam@...il.com, gregkh@...uxfoundation.org,
        info@...ux.net, kernel@...gutronix.de,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk,
        mturquette@...libre.com, oleksandr.suvorov@...adex.com,
        s.hauer@...gutronix.de, sfr@...b.auug.org.au, shawnguo@...nel.org,
        tglx@...utronix.de, yuehaibing@...wei.com
Cc:     dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH V2 3/9] clk: imx: Support building SCU clock driver as module

Quoting Aisheng Dong (2020-06-23 02:00:47)
> > From: Stephen Boyd <sboyd@...nel.org>
> > Sent: Tuesday, June 23, 2020 4:34 PM
> > Subject: RE: [PATCH V2 3/9] clk: imx: Support building SCU clock driver as
> > module
> > 
> > Quoting Aisheng Dong (2020-06-22 20:42:19)
> > > > From: Stephen Boyd <sboyd@...nel.org>
> > > > Sent: Saturday, June 20, 2020 11:28 AM
> > > > Subject: RE: [PATCH V2 3/9] clk: imx: Support building SCU clock
> > > > driver as module
> > > >
> > > > Quoting Aisheng Dong (2020-06-17 18:58:51)
> > > > > > From: Anson Huang <anson.huang@....com>
> > > > > > > > +obj-$(CONFIG_MXC_CLK_SCU) += mxc-clk-scu.o
> > > > > > >
> > > > > > > Like i.MX pinctrl, I'm not sure if it's really necessary to
> > > > > > > build core libraries as modules. Probably the simplest way is
> > > > > > > only building platform drivers part as module. And leave those
> > > > > > > core libraries
> > > > built in kernel.
> > > > > > > This may make the code a bit cleaner.
> > > > > > >
> > > > > >
> > > > > > Will discuss this with Linaro guys about it, previous
> > > > > > requirement I received is all SoC specific modules need to be built as
> > module.
> > > > > >
> > > > >
> > > > > Okay. AFAIK it's not conflict.
> > > > > You still make drivers into modules.
> > > > > Only difference is for those common libraries part, we don't
> > > > > convert them into module Which is less meaningless.
> > > > >
> > > >
> > > > What is the benefit of making the core part of the SoC driver not a module?
> > >
> > > Usually we could try to build it as module if it's not hard.
> > >
> > > One question is sometimes those core part are shared with some platforms
> > which can't built as module.
> > > For i.MX case, it's mainly patch 4:
> > > [V2,4/9] clk: imx: Support building i.MX common clock driver as module
> > >
> > >
> > > Those libraries are also used by i.MX6&7 which can't build as module.
> > > So we need an extra workaround patch to forcely 'select' it under
> > > arch/arm/mach-imx/Kconfig [V2,2/9] ARM: imx: Select MXC_CLK for
> > > ARCH_MXC
> > > Then the users can't configure it as module in order to not break build.
> > >
> > > If build-in those common libraries, the implementation could be a bit easier
> > and cleaner.
> > > So I'm not sure if we still have to build them as module.
> > > How would you suggest for such case?
> > 
> > Stop using 'select MXC_CLK' when requiring the core library code?
> > Instead, make it a 'depends' and then that will make depending modules (i.e. the
> > SoC files) that want to be builtin force the core module to be builtin too. Other
> > modular configs that depend on the core will still be modular.
> > 
> 
> It seems not work.
> Patch 4 already changes it to depend on ARCH_MXC which can only be 'Y'.
> [V2,4/9] clk: imx: Support building i.MX common clock driver as module
> diff --git a/drivers/clk/imx/Kconfig b/drivers/clk/imx/Kconfig
> index ded0643..678113b 100644
> --- a/drivers/clk/imx/Kconfig
> +++ b/drivers/clk/imx/Kconfig
> @@ -1,8 +1,8 @@ 
>  # SPDX-License-Identifier: GPL-2.0
>  # common clock support for NXP i.MX SoC family.
>  config MXC_CLK
> -       bool
> -       def_bool ARCH_MXC
> +       tristate "IMX clock"
> +       depends on ARCH_MXC
> 
> But user can still set MXC_CLK to be m, either via make menuconfig or defconfig.

Isn't that what we want? Why does ARCH_MXC being enabled mandate that it
is builtin? Is some architecture level code calling into the clk
driver?