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Re: [PATCH] ARM: s3c64xx: don't select ARM_AMBA from S3C64XX_PL080

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  Re: [PATCH] ARM: s3c64xx: don't select ARM_AMBA from S3C64XX_PL080 Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-05-31 22:00 +0200
    Re: [PATCH] ARM: s3c64xx: don't select ARM_AMBA from S3C64XX_PL080 Arnd Bergmann <arnd@arndb.de> - 2017-05-31 22:30 +0200
      Re: [PATCH] ARM: s3c64xx: don't select ARM_AMBA from S3C64XX_PL080 Mathieu Poirier <mathieu.poirier@linaro.org> - 2017-06-01 16:50 +0200

#1654592 — Re: [PATCH] ARM: s3c64xx: don't select ARM_AMBA from S3C64XX_PL080

On Wed, May 24, 2017 at 05:58:34PM +0200, Arnd Bergmann wrote:
> While trying a fix a build warning unrelated to s3c64xx, I ran into
> a circular dependency:
> 
> drivers/i2c/Kconfig:7: symbol I2C is selected by FB_DDC
> drivers/video/fbdev/Kconfig:63: symbol FB_DDC is selected by FB_CYBER2000_DDC
> drivers/video/fbdev/Kconfig:381: symbol FB_CYBER2000_DDC depends on FB_CYBER2000
> drivers/video/fbdev/Kconfig:369: symbol FB_CYBER2000 depends on FB
> drivers/video/fbdev/Kconfig:5: symbol FB is selected by DRM_KMS_FB_HELPER
> drivers/gpu/drm/Kconfig:72: symbol DRM_KMS_FB_HELPER is selected by DRM_KMS_CMA_HELPER
> drivers/gpu/drm/Kconfig:137: symbol DRM_KMS_CMA_HELPER is selected by DRM_PL111
> drivers/gpu/drm/pl111/Kconfig:1: symbol DRM_PL111 depends on ARM_AMBA
> drivers/amba/Kconfig:1: symbol ARM_AMBA is selected by S3C64XX_PL080
> arch/arm/mach-s3c64xx/Kconfig:42: symbol S3C64XX_PL080 default value contains DMADEVICES
> drivers/dma/Kconfig:5: symbol DMADEVICES is selected by SND_SOC_SH4_SIU
> sound/soc/sh/Kconfig:29: symbol SND_SOC_SH4_SIU is selected by SND_SIU_MIGOR
> sound/soc/sh/Kconfig:59: symbol SND_SIU_MIGOR depends on I2C
> 
> The I2C and FB dependencies are hard to untangle, but I notice that
> S3C64XX_PL080 selecting ARM_AMBA is one piece of the puzzle that
> can easily be avoided, as ARCH_S3C64XX already select ARM_AMBA.
> Removing the redundant 'select' now can help us in the future if we
> run into a variation of the same dependency.

Yes, selecting ARM_AMBA from drivers is definitely not right; this
symbol should be selected only by platforms that want AMBA primecell
bus support, not by drivers, precisely because of these dependency
issues.

There's another case where ARM_AMBA is selected that probably needs
fixing - the coresight hwtracing code.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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#1654609

On Wed, May 31, 2017 at 9:58 PM, Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:
> On Wed, May 24, 2017 at 05:58:34PM +0200, Arnd Bergmann wrote:
> Yes, selecting ARM_AMBA from drivers is definitely not right; this
> symbol should be selected only by platforms that want AMBA primecell
> bus support, not by drivers, precisely because of these dependency
> issues.
>
> There's another case where ARM_AMBA is selected that probably needs
> fixing - the coresight hwtracing code.

[Adding Mathieu to cc]

Mathieu,

do you remember how we ended up with this?

menuconfig CORESIGHT
       bool "CoreSight Tracing Support"
       select ARM_AMBA

As Russell says, probably shouldn't select that symbol, most likely
we want either the individual drivers that register an amba_driver to have
a 'depends on ARM_AMBA' or alternatively replace the 'select' with 'depends
on' for the entire subsystem.

        Arnd

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#1655203

On 31 May 2017 at 14:25, Arnd Bergmann <arnd@arndb.de> wrote:
> On Wed, May 31, 2017 at 9:58 PM, Russell King - ARM Linux
> <linux@armlinux.org.uk> wrote:
>> On Wed, May 24, 2017 at 05:58:34PM +0200, Arnd Bergmann wrote:
>> Yes, selecting ARM_AMBA from drivers is definitely not right; this
>> symbol should be selected only by platforms that want AMBA primecell
>> bus support, not by drivers, precisely because of these dependency
>> issues.
>>
>> There's another case where ARM_AMBA is selected that probably needs
>> fixing - the coresight hwtracing code.
>
> [Adding Mathieu to cc]
>
> Mathieu,
>
> do you remember how we ended up with this?

That was part of the initial driver submission that happened a couple
of years ago.  The driver depended on AMBA and as such I added the
"select", not knowing it was preferable to have a "depends".

>
> menuconfig CORESIGHT
>        bool "CoreSight Tracing Support"
>        select ARM_AMBA
>
> As Russell says, probably shouldn't select that symbol, most likely
> we want either the individual drivers that register an amba_driver to have
> a 'depends on ARM_AMBA' or alternatively replace the 'select' with 'depends
> on' for the entire subsystem.

I'm good with that.

Mathieu

>
>         Arnd

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