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

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Date:	Fri, 01 Apr 2011 14:10:04 -0700
From:	Kevin Hilman <khilman@...com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Detlef Vollmann <dv@...lmann.ch>, Ingo Molnar <mingo@...e.hu>,
	david@...g.hm, "Russell King - ARM Linux" <linux@....linux.org.uk>,
	Nicolas Pitre <nico@...xnic.net>,
	Tony Lindgren <tony@...mide.com>,
	Catalin Marinas <catalin.marinas@....com>,
	lkml <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Brown <davidb@...eaurora.org>,
	linux-omap@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [GIT PULL] omap changes for v2.6.39 merge window

Arnd Bergmann <arnd@...db.de> 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
>> >     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.  Part 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.  For 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.  If 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.

The kernel is only part of many open-source projects, and many of these
projects are still using older hardware because it's cheap, available
and hackable.  Supporting ARMv7 only might be a win for those selling
new hardware, but not necessarily a win for the broader open-source
community.

Kevin (obviously not speaking for my new employer)
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