linux-kernel - Re: [PATCH v2] arm64: Kconfig.platforms: Enable GPIO_DAVINCI for ARCH

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Date:   Thu, 11 Jul 2019 11:19:47 +0530
From:   Keerthy <j-keerthy@...com>
To:     Nishanth Menon <nm@...com>
CC:     <t-kristo@...com>, <will.deacon@....com>,
        <catalin.marinas@....com>, <shawnguo@...nel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <lokeshvutla@...com>
Subject: Re: [PATCH v2] arm64: Kconfig.platforms: Enable GPIO_DAVINCI for
 ARCH_K3



On 29/06/19 2:07 AM, Nishanth Menon wrote:
> On 09:08-20190628, Keerthy wrote:
> [..]
>>>> +	select GPIO_SYSFS
>>>> +	select GPIO_DAVINCI
>>>
>>>
>>> Could you help explain the logic of doing this? commit message is
>>> basically the diff in English. To me, this does NOT make sense.
>>>
>>> I understand GPIO_DAVINCI is the driver compatible, but we cant do this for
>>> every single SoC driver that is NOT absolutely mandatory for basic
>>> functionality.
>>
>> In case of ARM64 could you help me find the right place to enable
>> such SoC specific configs?
> 
> Is'nt that what defconfig is supposed to be all about?
> 
> arch/arm64/configs/defconfig
> 
>>
>>>
>>> Also keep in mind the impact to arm64/configs/defconfig -> every single
>>> SoC in the arm64 world will be now rebuild with GPIO_SYSFS.. why force
>>> that?
>>
>> This was the practice in arm32 soc specific configs like
>> omap2plus_defconfig. GPIO_SYSFS was he only way to validate. Now i totally
>> understand your concern about every single SoC rebuilding but now where do
>> we need to enable the bare minimal GPIO_DAVINCI config?
> 
> Well, SYSFS, I cannot agree testing as the rationale in
> Kconfig.platform. And, looking at [1], I see majority being mandatory
> components for the SoC bootup. However, most of the "optional" drivers
> go into arm64 as defconfig (preferably as a module?) and if you find a
> rationale for recommending DEBUG_GPIO, you could propose that to the
> community as well.
> 
> Now, Thinking about this, I'd even challenge the current list of configs as
> being "select". I'd rather do an "imply"[2] - yes, you need this for the
> default dtb to boot, however a carefully carved dtb could boot with
> lesser driver set to get a smaller (and less functional) kernel.
> 
>>
>> v1 i received feedback from Tero to enable in Kconfig.platforms. Hence i
>> shifted to this approach.
> 
> I noticed that you were posting a v2, for future reference, please use
> diffstat section to point to lore/patchworks link to point at v1 (I
> did notice you mentioned you had an update, thanks - link will help
> catch up on older discussions). This helps a later revision reviewer
> like me to get context.
> 
> Tero, would you be able to help with a better rationale as to where the
> boundaries are to be in your mind, rather than risk every single
> peripheral driver getting into ARCH_K3?

Tero,

Could you point me to a better place for enabling?

- Keerthy

> 
> As of right now, I'd rather we do not explode the current list out of
> bounds. NAK unless we can find a better rationale.
> 
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/Kconfig.platforms
> [2] https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt
>