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

[Paul Cercueil]

Le dim. 26 juil. 2020 à 18:06, Krzysztof Kozlowski <krzk@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx> wrote:
> >  > Le ven. 24 juil. 2020 à 17:54, Krzysztof Kozlowski 
> > <krzk@xxxxxxxxxx> 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@xxxxxxxxxx> a écrit:
> >  > >>  > On Fri, 24 Jul 2020 at 17:19, Paul Cercueil 
> > <paul@xxxxxxxxxxxxxxx>
> >  > >>  > 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@xxxxxxxxxx/
>
> Best regards,
> Krzysztof