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 12:53:55 +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 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.

So, I think it is NOT that tightly connected, it is because they are both for i.MX8 SoCs with SCU
inside, so they are put together in the Makefile.

If the export statement is acceptable, I think it is better to just keep it, make sense?

Thanks,
Anson