Re: [GIT PULL] omap changes for v2.6.39 merge window

[Catalin Marinas]

On Friday, 1 April 2011, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> On Friday 01 April 2011 23:10:04 Kevin Hilman wrote:
>> Arnd Bergmann <arnd@xxxxxxxx> writes:
>>
>> > On Friday 01 April 2011, Detlef Vollmann wrote:
>> >> On 04/01/11 15:54, Arnd Bergmann wrote:
>> >
>> >> > 9. All interesting work is going into a handful of platforms, all of which
>> >> > Â Â are ARMv7 based.
>> >> Define interesting.
>> >
>> > The ones that are causing the churn that we're talking about.
>> > Platforms that have been working forever and only need to get
>> > the occasional bug fix are boring, i.e. not the problem.
>>
>> I'm not sure I follow the ARMv7-only thinking either.
>>
>> Picking ARMv7 only would be a good way to avoid part of the problem, but
>> IMO, it doesn't really address the root causes. ÂPart of the ugliness of
>> the platform-specific hackery (and the "churn" to clean some of it up)
>> is precisely due to support for multiple ARM architecture versions, and
>> the various SoCs in a family that use them. ÂFor example, linux-omap
>> supports OMAP1 (ARMv5), OMAP2 (ARMv6), OMAP3 (ARMv7) and OMAP4 (ARMv7
>> SMP), and OMAP2/3/4 in a single binary.
>>
>> Also, since we've only very recently got to the point of being able to
>> support ARMv6 + ARMv7 UP & SMP in the same kernel, making a decision now
>> that only ARMv7 is important seems like a step backwards. ÂIf the
>> ultimate goal is getting to a point where we have infrastrucure that can
>> be cross-SoC, surely this same infrastrucure should support multiple ARM
>> architecture revisions.
>
> Yes, forget about the ARMv7 part of my proposal, that was not a main point.
>
> If we decide to have a new clean platform variant the way I suggested,
> it would be nice to support all machines in a single kernel binary,
> and at least v6+v7 is a solved problem.
>
> Supporting a second kernel binary up to v5 with the same source is also
> simple, as would be big-endian/little-endian variants, or thumb2/arm variants.
> We might not want to do all combinations from the start though, and I would
> choose ARMv6/v7-thumb2-le simply because that's what Linaro is focusing
> on. The idea is to start with a clearly defined set, but write the code
> in a way that makes it possible to extend in other directions.

Thumb-2 is ARMv7 only. If you want a v6+v7 binary it would need to be
compiled to ARM.


-- 
Catalin
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