[RFC PATCH] arm64: defconfig: add config fragment for Freescale SoCs

[Catalin Marinas]

On Thu, Apr 14, 2016 at 09:21:25AM -0500, Stuart Yoder wrote:
> Add a config fragment enabling a reasonably useful set of
> devices and options for Freescale ARM v8 SoCs.

A gentle NAK ;).

> I realize that we are trying to avoid the defconfig hell in arch/arm with 100+
> defconfigs, but the single defconfig in arch/arm64 has some problems too.

Can we address these problems in defconfig?

> I think what we want with arch/arm64/config are some reasonable in-kernel
> defconfigs/fragments with built-in drivers for convenience.

A hard requirement for arm64 is single Image and having all SoCs in
defconfig is a good way to regularly test this.

I am aware that at some point the defconfig size will get too big but
that's when (ideally before) we should put effort into building more
stuff as loadable modules.

> The proposal is to allow a chip vendor 1 vendor-specific kconfig fragment
> to cover all their chips, allowing them to _override_ the default config
> options in defconfig.  One specific issue we have is that due to the ls2080a
> physical address map, the combination of 4KB pages and 39-bit VA does not
> allow us to see all our DDR.  And, thus we need CONFIG_ARM64_VA_BITS_48=y.

And I'm fine to add this to defconfig. We had a case for Seattle needing
48-bit VA but we eventually decoupled the number of levels for idmap and
swapper. If it can't be addressed in a similar way on ls2080a, we may
need to increase the VA space to 48-bit.

> Allowing us to have a freescale.config gives us the flexibility of
> adding Freescale specific options without having to keep this in
> some other external repo.  It also keeps vendor specific clutter
> out of the base defconfig.  With the number of new armv8 chips 
> coming out the single defconfig is going to produce increasingly
> large kernels, since all drivers are built-in.

As I said, for the time being please add all the sane the options to
defconfig. I want to be able to build a defconfig and run on all
supported SoCs.

> +CONFIG_STAGING=y

Well, apart from this. You should put effort in getting the required
drivers out of staging.

-- 
Catalin