Subject: Kirkwood, kernel 3.2, vmalloc region overlap, not starting up

From: [email-masked] (Nils Faerber)
Date: Tue, 07 Feb 2012 18:01:02 +0100

Am 07.02.2012 17:51, schrieb Russell King - ARM Linux:
> On Tue, Feb 07, 2012 at 05:18:38PM +0100, Andrew Lunn wrote:
>>> Apart from my joy - the basic reason for that change would be still
>>> interesting? Does this only apply to Kirwoods or my special board?
>>
>> I think the conversation fizzled out without coming to a conclusion
>> what is wrong. Look back in the archives and see what you can find.
>> The problem hits kirkwood, but i don't know if it also affects other
>> Orion based processors. u-boot also play a role in the problem...
> 
> I think what's going on (what's suggested by the uboot patch) is that
> uboot leaves the L2 cache enabled, and then passes control over to
> the kernel decompressor.
> 
> The kernel decompressor starts, and enables the L1 cache.  This
> unexpectedly enables the L2 cache as well.  However, the decompressor
> is not L2 cache aware, and only cleans the L1 cache.
> 
> The decompressor finishes, flushes the L1 cache, and disables the L1
> cache (and, because of the way things work, disables the dirty L2
> cache.)
> 
> We're now in the situation where the kernel text/data may or may not
> be in RAM, and therefore may or may not be executable.
> 
> I don't think that's Nils problem.
> 
> But why you've both identified that turning off the V2P stuff fixes it,
> I'm not sure.  It needs debugging (it needs me or someone else to cook
> up a patch to get some information out of - explicitly - Nils system)
> so that we can work out what's going on there.
> 
> The theory is, the V2P stuff should be able to calculate the physical
> offset irrespective of the kernel placement, and so having it enabled
> should be totally transparent.  Obviously, something is going wrong.
> As yet we don't know what's causing Nils problem.
> 
> If no one gets there before me, then I'll post a patch for Nils to run
> with to get some information from his kernel sometime in the next few
> days, assuming these messages don't get too buried and I don't forget.

If you have anything for me to try I will gladly do it, no problem!

The same issue should also hit most of the other Kirkwood based systems
so finding a fix for my TK71 should also resolve issues on quite some
other boards.

Cheers
  nils

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