linux-kernel - Re: [PATCH v2] phy: tegra: depend on COMMON

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Message-ID: <f0fbc7eb-f180-453c-de64-64c3d00958f8@canonical.com>
Date:   Tue, 16 Mar 2021 17:20:49 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-tegra@...r.kernel.org, Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] phy: tegra: depend on COMMON_CLK to fix compile tests

On 16/03/2021 17:14, Dmitry Osipenko wrote:
> 16.03.2021 18:51, Krzysztof Kozlowski пишет:
>>>>
>>>> But if COMMON_CLK is disabled, then include/linux/clk.h provides a stub
>>>> for clk_get_parent(), meaning that MIPS has its own COMMON_CLK, no?
>>>
>>> Hi,
>>>
>>> It depends on the platform. Not all of them implement every clk API,
>>> so you can have failures:
>>> https://lore.kernel.org/lkml/202102170017.MgPVy7aZ-lkp@intel.com/
>>
>> Ah, you mentioned the stub, so let me clarify more. The common clk
>> stubs are not used for cases like !COMMON_CLK && HAVE_LEGACY_CLK (or
>> HAVE_CLK, I don't remember). This is why you can have a MIPS platform
>> defining some of the clock operations thus not using COMMON_CLK at all
>> (and neither the stubs).
> 
> I see now that the stubs depend on CONFIG_HAVE_CLK and not COMMON_CLK,
> thanks.
> 
> This raises question about why those platforms select CONFIG_HAVE_CLK,
> while not implementing it fully. Sounds like a better fix should be to
> add the missing stubs to the MIPS clk implementation, which should avoid
> the need to patch each driver individually.
> 
> https://elixir.bootlin.com/linux/v5.12-rc3/source/arch/mips/ar7/clock.c#L489

If such stubs as pointed by you are accepted, then indeed it would be
better approach.

Best regards,
Krzysztof