Re: nommu build failures on ARM in linux-next

[Paul Gortmaker <paul.gortmaker@windriver.com>]

[Re: nommu build failures on ARM in linux-next] On 30/05/2014 (Fri 00:40) Russell King - ARM Linux wrote:

> On Thu, May 29, 2014 at 07:55:34PM +0100, Russell King - ARM Linux wrote:
> > On Thu, May 29, 2014 at 12:53:51PM -0400, Paul Gortmaker wrote:
> > > Hi Russell,
> > > 
> > > The allnoconfig builds in linux-next fail because __clear_cr
> > > lives in mmu.c without any stub or similar in nommu.c
> > > 
> > > Introduced by:
> > > 
> > > commit 247e4fff3aa927ad069447e6da05bb966b70dece
> > > Author: Russell King <rmk+kernel@arm.linux.org.uk>
> > > Date:   Sun Apr 13 18:57:29 2014 +0100
> > > 
> > >     ARM: provide common method to clear bits in CPU control register
> > >     
> > > Sample failure:
> > >   http://kisskb.ellerman.id.au/kisskb/buildresult/11264405/
> > 
> > ALIGNMENT_TRAP depends on CPU_CP15_MMU, so it's quite reasonable that
> > __clear_cr should exist in this case - but it doesn't because it's in
> > mmu.c.  I guess we need __clear_cr moved to arch/arm/kernel/setup.c.
> 
> I've been looking at doing this, and while it can be done by applying
> a patch on top, that's not my preferred solution.
> 
> However, my preferred solution (which is to fix the commit) needs a bit
> of rework of the patch series, and given the number of patches I'm
> carrying right now, I'm just going to drop the branch out of linux-next
> and hold it off until the following merge window instead.
> 
> Even so, I suspect even with this build problem solved, that's not going
> to be the end of the story for noMMU breakage... it's certainly something
> that gets very little testing by anyone.  I suspect it should be removed
> from the mainline kernel tree rather than being a constant source of these
> kinds of problems.

One doesn't have to look very far to see that I'm in favour of pushing
obsolete options/drivers/subsystems off a cliff if I can get away with
it, so that we don't get crushed under our own weight/complexity.

So if you really think it is time for ARM noMMU to go, I'll volunteer to
craft up a removal series for you for 3.17 -- just say the word.

Paul.
--

> 
> -- 
> FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
> improving, and getting towards what was expected from it.