linux-kernel - Re: [PATCH 1/2] memory: tegra: Add missing dependencies

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Date:   Thu, 10 Jun 2021 08:42:16 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Dmitry Osipenko <digetx@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Jon Hunter <jonathanh@...dia.com>, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] memory: tegra: Add missing dependencies

On 09/06/2021 19:00, Thierry Reding wrote:
> On Wed, Jun 09, 2021 at 03:19:12PM +0200, Krzysztof Kozlowski wrote:
>> On 09/06/2021 13:58, Dmitry Osipenko wrote:
>>> 09.06.2021 14:28, Thierry Reding пишет:
>>>> From: Thierry Reding <treding@...dia.com>
>>>>
>>>> When enabling the COMPILE_TEST Kconfig option, the Tegra memory
>>>> controller can be built without ARCH_TEGRA being selected. However, the
>>>> driver implicitly depends on some symbols pulled in via ARCH_TEGRA,
>>>> which causes the build to break.
>>>>
>>>> Add explicit dependencies for OF_EARLY_FLATTREE and OF_RESERVED_MEM to
>>>> the Tegra MC Kconfig option to make sure they are selected even if
>>>> ARCH_TEGRA is not.
>>>>
>>>> Reported-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
>>>> Signed-off-by: Thierry Reding <treding@...dia.com>
>>>> ---
>>>>  drivers/memory/tegra/Kconfig | 2 ++
>>>>  1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/memory/tegra/Kconfig b/drivers/memory/tegra/Kconfig
>>>> index f9bae36c03a3..ecfb071fc4f4 100644
>>>> --- a/drivers/memory/tegra/Kconfig
>>>> +++ b/drivers/memory/tegra/Kconfig
>>>> @@ -48,6 +48,8 @@ config TEGRA124_EMC
>>>>  config TEGRA210_EMC_TABLE
>>>>  	bool
>>>>  	depends on ARCH_TEGRA_210_SOC || COMPILE_TEST
>>>> +	select OF_EARLY_FLATTREE
>>>> +	select OF_RESERVED_MEM
>>>>  
>>>>  config TEGRA210_EMC
>>>>  	tristate "NVIDIA Tegra210 External Memory Controller driver"
>>>>
>>>
>>> Will this work if CONFIG_OF is disabled?
>>
>> Yeah, good question. That's why I propose "depends on". No issues with
>> unmet or circular dependencies.
> 
> I couldn't find a way to make this work with "depends on" because
> OF_RESERVED_MEM is not user-visible and the only way to get it enabled
> is if something also selects OF_EARLY_FLATTREE, which is only ever done
> at the architecture Kconfig level (and for OF unit testing).
> 
> So switching this to a "depends on" causes the TEGRA210_EMC never to get
> enabled.

Right.

> 
> However, with OF disabled, the above causes issues because it can lead
> to unmet direct dependencies. That, in turn, can be fixed by appending
> && OF to the COMPILE_TEST branch, which seems like a good enough
> compromise.
> 
> Here's what I have on top of the above patch and that seems to do the
> trick.
> 
> --- >8 ---
> diff --git a/drivers/memory/tegra/Kconfig b/drivers/memory/tegra/Kconfig
> index ecfb071fc4f4..1c553895160c 100644
> --- a/drivers/memory/tegra/Kconfig
> +++ b/drivers/memory/tegra/Kconfig
> @@ -47,13 +47,13 @@ config TEGRA124_EMC
>  
>  config TEGRA210_EMC_TABLE
>  	bool
> -	depends on ARCH_TEGRA_210_SOC || COMPILE_TEST
> +	depends on ARCH_TEGRA_210_SOC || (COMPILE_TEST && OF)
>  	select OF_EARLY_FLATTREE
>  	select OF_RESERVED_MEM
>  
>  config TEGRA210_EMC
>  	tristate "NVIDIA Tegra210 External Memory Controller driver"
> -	depends on ARCH_TEGRA_210_SOC || COMPILE_TEST
> +	depends on ARCH_TEGRA_210_SOC || (COMPILE_TEST && OF)
>  	select TEGRA210_EMC_TABLE
>  	help
>  	  This driver is for the External Memory Controller (EMC) found on
> --- >8 ---
> 
> So in a nutshell this will only get compile-tested if OF is enabled, but
> then it will select OF_RESERVED_MEM and OF_EARLY_FLATTREE to get the
> required symbols.

Could be also separate "depends on OF", even though it is included in
ARCH_TEGRA_XXX, but I am fine with this here.

Best regards,
Krzysztof