linux-kernel - RE: [PATCH V4 3/5] clk: imx: Support building i.MX common clock driver as module

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Date:   Thu, 2 Jul 2020 07:12:36 +0000
From:   Anson Huang <anson.huang@....com>
To:     Arnd Bergmann <arnd@...db.de>, Dong Aisheng <dongas86@...il.com>
CC:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.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>,
        linux-clk <linux-clk@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH V4 3/5] clk: imx: Support building i.MX common clock
 driver as module

Hi, Arnd


> Subject: Re: [PATCH V4 3/5] clk: imx: Support building i.MX common clock
> driver as module
> 
> On Thu, Jul 2, 2020 at 8:40 AM Dong Aisheng <dongas86@...il.com> wrote:
> > On Thu, Jul 2, 2020 at 2:11 PM Anson Huang <anson.huang@....com>
> wrote:
> > > > Subject: Re: [PATCH V4 3/5] clk: imx: Support building i.MX common
> > > > clock
> > >
> > > I am fine of adding the '#ifndef MODULE' to imx_clk_disable_uart()
> > > and imx_keep_uart_clocks_param() as well in next patch series.
> > > Others like ' imx_keep_uart_clocks ' and imx_register_uart_clocks() need to
> be kept always built, since they are used by each clock driver no matter
> built-in or module build.
> > >
> > > So that means I have to add another 'ifndef MODULE' or I need to
> > > adjust some code sequence to make those code can be built-out in
> > > same block and just use single 'ifndef MODULE', I think adjust the code
> sequence should be better, will go with this way.
> >
> > What if we  condionally compile it in clk.h? Will that be easiser?
> 
> Yes, that's what I expected to see in v4 after the previous discussion. If
> imx_register_uart_clocks() is an empty inline function, then the arrays passed
> to it are unused and also get dropped by the compiler.
> 
> The question is whether the #ifdef check in the header to test for MODULE
> (only calling it if this particular soc has a built-in clk driver, which is sufficient)
> or for IS_MODULE(CONFIG_MXC_CLK) (call it if _any_ clk driver is built-in and
> the function exists, which leaves extra code in the driver but is a more
> conventional check).
> 

So you prefer to add an empty inline function for imx_register_uart_clocks() with check
of MODULE build? Even with this, we still need to add MODULE build check to whole block
of this earlycon uart clock handler in imx/clk.c.

Thanks,
Anson