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

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Date:   Mon, 29 Jun 2020 14:52:09 +0000
From:   Anson Huang <anson.huang@....com>
To:     Arnd Bergmann <arnd@...db.de>
CC:     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

Hi, Arnd

> 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:
> > > Subject: Re: [PATCH V3 04/10] clk: imx: Support building SCU clock
> > > driver as module
> > >
> > > On Mon, Jun 29, 2020 at 8:06 AM Anson Huang <Anson.Huang@....com>
> > > wrote:
> > >
> > > > --- a/drivers/clk/imx/Makefile
> > > > +++ b/drivers/clk/imx/Makefile
> > > > @@ -21,9 +21,9 @@ obj-$(CONFIG_MXC_CLK) += \
> > > >         clk-sscg-pll.o \
> > > >         clk-pll14xx.o
> > > >
> > > > -obj-$(CONFIG_MXC_CLK_SCU) += \
> > > > -       clk-scu.o \
> > > > -       clk-lpcg-scu.o
> > > > +mxc-clk-scu-objs += clk-lpcg-scu.o mxc-clk-scu-objs += clk-scu.o
> > > > +obj-$(CONFIG_MXC_CLK_SCU) += mxc-clk-scu.o
> > >
> > > It looks like the two modules are tightly connected, one is useless
> > > without the other. How about linking them into a combined module and
> > > dropping the export statement?
> > >
> >
> > From HW perspective, the SCU clock driver and LPCG SCU clock driver
> > are different, SCU clock driver is for those clocks controlled by
> > system controller (M4 which runs a firmware), while LPCG SCU clock is
> > for those clock gates inside module, which means AP core can control it
> directly via register access, no need to via SCU API.
> 
> 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

Thanks,
Anson