linux-kernel - Re: [PATCH] mux: mmio: Fix missing CONFIG_REGMAP

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Message-Id: <8819720e-dada-4489-a867-c4de0f95a003@app.fastmail.com>
Date: Thu, 15 May 2025 17:30:23 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Krzysztof Kozlowski" <krzysztof.kozlowski@...aro.org>,
 "Peter Rosin" <peda@...ntia.se>, "Andrew Lunn" <andrew+netdev@...n.ch>,
 "David S . Miller" <davem@...emloft.net>,
 "Eric Dumazet" <edumazet@...gle.com>, "Jakub Kicinski" <kuba@...nel.org>,
 "Paolo Abeni" <pabeni@...hat.com>, "Andrew Davis" <afd@...com>,
 linux-kernel@...r.kernel.org, Netdev <netdev@...r.kernel.org>
Cc: "kernel test robot" <lkp@...el.com>,
 "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
 "Samuel Holland" <samuel@...lland.org>
Subject: Re: [PATCH] mux: mmio: Fix missing CONFIG_REGMAP_MMIO

On Thu, May 15, 2025, at 16:05, Krzysztof Kozlowski wrote:
> MMIO mux uses now regmap_init_mmio(), so one way or another
> CONFIG_REGMAP_MMIO should be enabled, because there are no stubs for
> !REGMAP_MMIO case:
>
>   ERROR: modpost: "__regmap_init_mmio_clk" [drivers/mux/mux-mmio.ko] undefined!
>
> REGMAP_MMIO should be, because it is a non-visible symbol, but this
> causes a circular dependency:
>
>   error: recursive dependency detected!
>   symbol IRQ_DOMAIN is selected by REGMAP
>   symbol REGMAP default is visible depending on REGMAP_MMIO
>   symbol REGMAP_MMIO is selected by MUX_MMIO
>   symbol MUX_MMIO depends on MULTIPLEXER
>   symbol MULTIPLEXER is selected by MDIO_BUS_MUX_MULTIPLEXER
>   symbol MDIO_BUS_MUX_MULTIPLEXER depends on MDIO_DEVICE
>   symbol MDIO_DEVICE is selected by PHYLIB
>   symbol PHYLIB is selected by ARC_EMAC_CORE
>   symbol ARC_EMAC_CORE is selected by EMAC_ROCKCHIP
>   symbol EMAC_ROCKCHIP depends on OF_IRQ
>   symbol OF_IRQ depends on IRQ_DOMAIN
>
> ... which we can break by changing dependency in EMAC_ROCKCHIP from
> OF_IRQ to OF.
>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: 
> https://lore.kernel.org/oe-kbuild-all/202505150312.dYbBqUhG-lkp@intel.com/
> Fixes: 61de83fd8256 ("mux: mmio: Do not use syscon helper to build 
> regmap")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>
> ---
>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Samuel Holland <samuel@...lland.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> ---

I'm unable to test this on my randconfig setup, but the patch
looks sensible to me.

Acked-by: Arnd Bergmann <arnd@...db.de>

In the dependency loop above, I think the PHYLIB bit should also
be changed, but that is an independent problem.

I see that OF_IRQ still depends on !SPARC, which may be another
source for problems, so it's possible that anything that tries
to use OF_IRQ causes a build failure on sparc as well.

     Arnd