linux-kernel - Re: [PATCH V3 04/10] clk: imx: Support building SCU clock driver as module

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Message-ID: <CAA+hA=TYuSk=P4D_D0_Rv1O2AAB3UvYrNXToptPJjEsjECquUw@mail.gmail.com>
Date:   Tue, 30 Jun 2020 11:55:50 +0800
From:   Dong Aisheng <dongas86@...il.com>
To:     Anson Huang <anson.huang@....com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        "oleksandr.suvorov@...adex.com" <oleksandr.suvorov@...adex.com>,
        Stefan Agner <stefan.agner@...adex.com>,
        Peng Fan <peng.fan@....com>, Abel Vesa <abel.vesa@....com>,
        Aisheng Dong <aisheng.dong@....com>,
        Andy Duan <fugang.duan@....com>,
        Daniel Baluta <daniel.baluta@....com>,
        YueHaibing <yuehaibing@...wei.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Al Viro <viro@...iv.linux.org.uk>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH V3 04/10] clk: imx: Support building SCU clock driver as module

On Tue, Jun 30, 2020 at 5:16 AM Anson Huang <anson.huang@....com> wrote:
>
> Hi, Arnd
>
>
> > Subject: Re: [PATCH V3 04/10] clk: imx: Support building SCU clock driver as
> > module
> >
> > On Mon, Jun 29, 2020 at 4:52 PM Anson Huang <anson.huang@....com>
> > wrote:
> > > > Subject: Re: [PATCH V3 04/10] clk: imx: Support building SCU clock
> > > > driver as module On Mon, Jun 29, 2020 at 2:53 PM Anson Huang
> > <anson.huang@....com> wrote:
> > > >
> > > > Sorry, I misread the patch in multiple ways. First of all, you
> > > > already put clk-scu.o and clk-lpcg-scu.o files into a combined
> > > > loadable module, and I had only looked at clk-scu.c.
> > > >
> > > > What I actually meant here was to link clk-scu.o together with
> > > > clk-imx8qxp.o (and possibly future chip-specific files) into a
> > > > loadable module and drop the export.
> > >
> > > Sorry, could you please advise more details about how to do it in Makefile?
> > > I tried below but it looks like NOT working. multiple definition of
> > module_init() error reported.
> > >
> > > obj-$(CONFIG_MXC_CLK_SCU) := clk-imx.o clk-imx-y += clk-scu.o
> > > clk-lpcg-scu.o
> > > clk-imx-$(CONFIG_CLK_IMX8QXP) += clk-imx8qxp.o clk-imx8qxp-lpcg.o
> >
> > Right, you can't have multiple module_init() in a module, so what I suggested
> > earlier won't work any more as soon as you add a second chip that uses the
> > clk-scu driver, and then you have to use separate modules, or some hack that
> > calls the init functions one at a time, which is probably worse.
> >
> > If it's only imx8qxp, you can do it like this:
> >
> > obj-$(CONFIG_MXC_CLK_SCU) := clk-imx-scu.o clk-imx-lpcg.o
> > clk-imx-scu-y         += clk-scu.o clk-imx8qxp.o
> > clk-imx-lpcq-scu-y += clk-lpcg-scu.o clk-imx8qxp-lpcg.o
> >
> > If you already know that the scu driver is going to be used in future chips, then
> > just stay with what you have now, using a separate module per file, exporting
> > the symbols as needed.
> >
>
> Thanks, and yes, I know that scu clk driver will be used for future i.MX8X chips with
> SCU inside, the current i.MX8QXP clock driver can NOT cover all i.MX8X chips, so
> I will stay with the exporting symbols.
>

SCU clock driver is a common driver for all SCU based platforms.
Current i.MX8QXP SCU clock driver will be extended to support all
future SCU based platforms.
So theoretically clk-scu.o and clk-imx8qxp.o can be combined. LPCG  is similar.
Maybe you can give a try as Arnd suggested.

Regards
Aisheng

> Thanks,
> Anson