CONFIG_PIN_TLB and telnet problems

[David Gibson]

Ok, I think I've managed to reproduce the telnet problems with
CONFIG_PIN_TLB that Tom Rini and others have reported.  I encountered
problems telnetting to localhost on a 16MB EP405 (PVR 40110145) and on
a 32MB Walnut (PVR 401100C4).  I was unable to reproduce the problem
on any of the other 405GP machines I have, each of which as at least
64MB of RAM.

Interestingly, if I alter the CONFIG_PIN_TLB code so that it only pins
one entry (i.e. maps 16MB of RAM instead of 32MB) I can still
reproduce the problem on the EP405, but not on the Walnut.  It would
seem the problem only bites if the pinned allocation is as large or
larger than physical memory.

It's vaguely understandable that with two pinned entries it would
break on the 16MB machine: creating a mapping for more RAM than exists
is certainly a bug.  I don't yet know why there is a problem when the
mapping is exactly as large as RAM though.

--
David Gibson			| For every complex problem there is a
david at gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.  -- H.L. Mencken
http://www.ozlabs.org/people/dgibson

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