Re: [patch 0/2] ARM: Disable outer cache before kexec call

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On Thu, 2010-07-01 at 17:28 +0100, Thomas Gleixner wrote:
> On Thu, 1 Jul 2010, Catalin Marinas wrote:
> > On Thu, 2010-07-01 at 17:05 +0100, Thomas Gleixner wrote:
> > > The following patch series addresses the problem, that the kexec code
> > > does not disable the outer cache before disabling the inner cache and
> > > jumping into the new kernel. This results in random crashes of the new
> > > kernel.
> >
> > We may need other ways to work around this problem. There are platforms
> > like OMAP3 (I think) where the L2 cache cannot be disabled as Linux is
> > running in non-secure (normal) mode.
> 
> But it can disable the inner caches? That's weird.

That's because the CP15 SCTLR register is a banked one, so independent
configuration for secure and normal worlds.

The outer cache controller doesn't have banked registers and I'm not
even sure it has a notion of secure or non-secure cache line.

> > Cannot some extra cache flushing work around this problem?
> 
> We tried to keep the L2 on and just doing the l2x0_inv_all() call and
> it hangs.

You would probably need an l2x0_flush_all() function which does clean
+invalidate. If you only do invalidate you may just remove valid cache
lines that have reached the RAM.

We only use the l2x0_inv_all() prior to enabling the L2 cache.

-- 
Catalin


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