linux-kernel - Re: [PATCH] ARM: s3c64xx: don't select ARM_AMBA from S3C64XX

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Message-ID: <20170531195849.GD27796@n2100.armlinux.org.uk>
Date:   Wed, 31 May 2017 20:58:49 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Eric Anholt <eric@...olt.net>,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: 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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