On 05.03.2014 09:25, Sachin Kamat wrote:
On 25 February 2014 17:12, Arnd Bergmann <arnd@xxxxxxxx> wrote:
On Tuesday 25 February 2014, Olof Johansson wrote:
I disagree. I don't know what Samsung has in mind, but the revision of
the CPU doesn't have all that much to do with the rest of the SoC.
It's quite likely that some vendors (maybe not Samsung, but the same
concept applies) will ship 64-bit SoCs that are very similar to their
preceding 32-bit ones, same IP, similar busses, etc. I'm pretty sure
at least some vendors will do very close to that.
Right.
So, if EXYNOS4 and EXYNOS5 can share a compatible value when they use
different CPUs, then there's no reason that whatever future 64-bit
ones can also share it.
How about putting both 'samsung,exynos' and 'samsung,exynos4' in DT then
and having the platform code match exynos4 and exynos5 but not exynos?
That way, I think we are consistent and future-proof. Any code that needs
to know if it's running on some exynos version can just check for the
'samsung,exynos' compatible value and that will work on both arm32 and
arm64. Also, if we ever decide we want to run a 32-bit kernel on a 64-bit
exynos, we can just add 'samsung,exynos6' (or whatever number that will
be) to the list.
My usual disclaimer for this: You should never ever consider actually
running a 32-bit kernel on a 64-bit CPU, but at the same time there
shouldn't be any reason why it won't work either, given that we require
arm64 based systems to have all SoC specific code in drivers and we
can use the same drivers on arm32.
Kukjin, Tomasz,
What is your opinion about Arnd's suggestion?
I would still prefer introducing a generic string for 32-bit Exynos
SoCs, but I don't think it really matters a lot. I guess we can stick to
just exynos4 and exynos5 compatible strings then, as long as we can
merge the "board"-files and common.c together, since the code is pretty
much SoC-independent now.
Best regards,
Tomasz
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