Re: [PATCH v3 2/2] mtd: rawnand: ingenic: Limit MTD_NAND_JZ4780 to architecture only

Paul Cercueil
2020-07-26T16:12:45Z

Le dim. 26 juil. 2020 à 18:06, Krzysztof Kozlowski <krzk@kernel.org> a
écrit :
> On Sat, Jul 25, 2020 at 08:30:56PM +0200, Arnd Bergmann wrote:
>> On Sat, Jul 25, 2020 at 2:17 PM Paul Cercueil
>> <paul@crapouillou.net> wrote:
>> > Le ven. 24 juil. 2020 à 17:54, Krzysztof Kozlowski
>> <krzk@kernel.org> a
>> > écrit :
>> > > On Fri, Jul 24, 2020 at 05:50:06PM +0200, Paul Cercueil wrote:
>> > >> Le ven. 24 juil. 2020 à 17:33, Krzysztof Kozlowski
>> > >> <krzk@kernel.org> a écrit:
>> > >> > On Fri, 24 Jul 2020 at 17:19, Paul Cercueil
>> <paul@crapouillou.net>
>> > >> > wrote:
>> > >>
>> > >> On MIPS, the SoC selection is a Kconfig "choice", so you can
>> only
>> > >> support
>> > >> one SoC family, unfortunately.
>> > >
>> > > Let's say someone selected then some other architecture
>> > > (MIPS_ALCHEMY).
>> > > They could select this MTD driver.
>> > >
>> > > Does it mean they would be able to run it on Ingenic hardware?
>> >
>> > In *theory* yes, as long as the Kconfig options that MACH_INGENIC
>> > selects are enabled, the kernel should boot and work on Ingenic
>> SoCs.
>>
>> Right now, this won't work yet, because there are platform specific
>> functions that are implemented by each of the platforms in
>> arch/mips,
>> e.g. arch/mips/generic/init.c and arch/mips/jz4740/setup.c.
>
> I would say even more - no DTS would be provided for such
> configuration.
> All Ingenic DTSes are included only with MACH_INGENIC. You cannot
> build
> a kernel working on Ingenic without MACH_INGENIC. Even in theory.

But the devicetree doesn't have to be built-in.

-Paul

>>
>> A lot of the newer platforms are part of arch/mips/generic
>> (CONFIG_MIPS_GENERIC), which roughly corresponds to
>> CONFIG_ARCH_MULTIPLATFORM on in arch/arm/.
>> Similarly, there are header files in arch/mips/include/asm/mach-*/
>> that conflict and you need to have the right one.
>>
>> To have more than one platform enabled, each one needs to
>> have all of that platform code converted to fit into the
>> MIPS_GENERIC framework. This can be a lot of work, but
>> I suppose the ingenic platform would be a candidate for
>> which this makes sense, as long as new SoCs of that family
>> still come out.
>
> I can therefore change the patch to:
> depends on MACH_INGENIC || MIPS_GENERIC || COMPILE_TEST
>
> Other solution is to leave MTD driver as is and for the memory driver
> go
> with my v2 approach:
> https://lore.kernel.org/lkml/20200724074038.5597-6-krzk@kernel.org/
>
> Best regards,
> Krzysztof
>