linux-kernel - Re: [PATCH v3 2/2] mtd: rawnand: ingenic: Limit MTD_NAND

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Date:   Sun, 26 Jul 2020 18:06:13 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>,
        Harvey Hunt <harveyhuntnexus@...il.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-kernel@...r.kernel.org,
        linux-mtd <linux-mtd@...ts.infradead.org>
Subject: Re: [PATCH v3 2/2] mtd: rawnand: ingenic: Limit MTD_NAND_JZ4780 to
 architecture only



Le sam. 25 juil. 2020 à 20:30, Arnd Bergmann <arnd@...db.de> a écrit :
> On Sat, Jul 25, 2020 at 2:17 PM Paul Cercueil <paul@...pouillou.net> 
> wrote:
>>  Le ven. 24 juil. 2020 à 17:54, Krzysztof Kozlowski 
>> <krzk@...nel.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@...nel.org> a écrit:
>>  >>  > On Fri, 24 Jul 2020 at 17:19, Paul Cercueil 
>> <paul@...pouillou.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.
> 
> 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.

It should be much less work now that the vast majority of 
arch/mips/jz4740 is gone. The code left is pretty much generic. I can 
have a look to convert it to the MIPS_GENERIC framework.

Although the code there is scary. Have a look at 
arch/mips/include/asm/{machine,mips_machine}.h, you'll see what I mean.

Anyway, I think we're way past the scope of this patch, so for this one:
Acked-by: Paul Cercueil <paul@...pouillou.net>

Cheers,
-Paul