[RFC PATCH] clk: imx8qxp: Unbreak auto module building for MXC_CLK_SCU

[Aisheng Dong]

> From: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
> Sent: Tuesday, November 24, 2020 8:18 PM
> 
> Automatic moudule building is broken by adding module support to i.MX8QXP
> clock driver. It can be tested by ARM defconfig + CONFIG_IMX_MBOX=m and
> CONFIG_MXC_CLK_SCU=m.
> 
> The compile breaks because the modules and source files are mixed.
> After fixing that, the build breaks because the SCU driver has no license or
> symbols, which are required by the CLK_IMX8QXP driver, are not properly
> exported.
> 
> The following patch is against -rc5:
> 
> Compile module clk-imx-scu.o which contains of clk-scu.o clk-lpcg-scu.o if
> CONFIG_MXC_CLK_SCU is enabled.
> Compile modules clk-imx8qxp.o and clk-imx8qxp-lpcg.o if
> CONFIG_CLK_IMX8QXP is enabled.
> Add EXPORT_SYMBOL_GPL() to functions which fail to resolve once
> CONFIG_CLK_IMX8QXP is enabled as module.
> Add License GPL to clk-scu.c.
> 

I think the simplest solution is make MXC_CLK_SCU to be invisible to users and can only
be selected by CLK_IMX8QXP option because currently clk-scu.o and clk-imx8qxp.o are built
together, it's meaningless and buggy to separate them. Longtermly they will be combined into
one driver file.

E.g
diff --git a/drivers/clk/imx/Kconfig b/drivers/clk/imx/Kconfig
index 3b393cb07295..dbacdd70af2e 100644
--- a/drivers/clk/imx/Kconfig
+++ b/drivers/clk/imx/Kconfig
@@ -5,7 +5,7 @@ config MXC_CLK
        depends on ARCH_MXC || COMPILE_TEST
 
 config MXC_CLK_SCU
-       tristate "IMX SCU clock"
+       tristate
        depends on ARCH_MXC || COMPILE_TEST
        depends on IMX_SCU && HAVE_ARM_SMCCC

> In -next it breaks additionally because device_is_bound() is not made available
> to modules.
> Any suggestions? Should the original commit be revoked?

See fixes here:
https://patchwork.kernel.org/project/linux-clk/cover/20201124100802.22775-1-aisheng.dong@nxp.com/

> 
> Fixes: e0d0d4d86c766 ("clk: imx8qxp: Support building i.MX8QXP clock driver
> as module")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
> ---
> 
>  drivers/clk/imx/Makefile       | 6 +++---
>  drivers/clk/imx/clk-lpcg-scu.c | 1 +
>  drivers/clk/imx/clk-scu.c      | 4 ++++
>  3 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/clk/imx/Makefile b/drivers/clk/imx/Makefile index
> dd6a737d060b4..b8bf9460c91d7 100644
> --- a/drivers/clk/imx/Makefile
> +++ b/drivers/clk/imx/Makefile
> @@ -26,9 +26,9 @@ obj-$(CONFIG_CLK_IMX8MN) += clk-imx8mn.o
>  obj-$(CONFIG_CLK_IMX8MP) += clk-imx8mp.o
>  obj-$(CONFIG_CLK_IMX8MQ) += clk-imx8mq.o
> 
> -obj-$(CONFIG_MXC_CLK_SCU) += clk-imx-scu.o clk-imx-lpcg-scu.o
> -clk-imx-scu-$(CONFIG_CLK_IMX8QXP) += clk-scu.o clk-imx8qxp.o
> -clk-imx-lpcg-scu-$(CONFIG_CLK_IMX8QXP) += clk-lpcg-scu.o
> clk-imx8qxp-lpcg.o
> +obj-$(CONFIG_MXC_CLK_SCU)	+= clk-imx-scu.o
> +clk-imx-scu-y			:= clk-scu.o clk-lpcg-scu.o

We can't do this because clk-scu  and clk-lpcg-scu are separate drivers.

Regards
Aisheng

> +obj-$(CONFIG_CLK_IMX8QXP)	+= clk-imx8qxp.o clk-imx8qxp-lpcg.o
> 
>  obj-$(CONFIG_CLK_IMX1)   += clk-imx1.o
>  obj-$(CONFIG_CLK_IMX25)  += clk-imx25.o diff --git
> a/drivers/clk/imx/clk-lpcg-scu.c b/drivers/clk/imx/clk-lpcg-scu.c index
> 1f0e44f921aee..336dce43da82d 100644
> --- a/drivers/clk/imx/clk-lpcg-scu.c
> +++ b/drivers/clk/imx/clk-lpcg-scu.c
> @@ -115,3 +115,4 @@ struct clk_hw *imx_clk_lpcg_scu(const char *name,
> const char *parent_name,
> 
>  	return hw;
>  }
> +EXPORT_SYMBOL_GPL(imx_clk_lpcg_scu);
> diff --git a/drivers/clk/imx/clk-scu.c b/drivers/clk/imx/clk-scu.c index
> b8b2072742a56..026a33606ae53 100644
> --- a/drivers/clk/imx/clk-scu.c
> +++ b/drivers/clk/imx/clk-scu.c
> @@ -9,6 +9,7 @@
>  #include <linux/clk-provider.h>
>  #include <linux/err.h>
>  #include <linux/slab.h>
> +#include <linux/module.h>
> 
>  #include "clk-scu.h"
> 
> @@ -132,6 +133,7 @@ int imx_clk_scu_init(void)  {
>  	return imx_scu_get_handle(&ccm_ipc_handle);
>  }
> +EXPORT_SYMBOL_GPL(imx_clk_scu_init);
> 
>  /*
>   * clk_scu_recalc_rate - Get clock rate for a SCU clock @@ -387,3 +389,5 @@
> struct clk_hw *__imx_clk_scu(const char *name, const char * const *parents,
> 
>  	return hw;
>  }
> +EXPORT_SYMBOL_GPL(__imx_clk_scu);
> +MODULE_LICENSE("GPL");
> --
> 2.29.2