Re: SPARSEMEM support for Atmel AT91SAM9G45 and M10

Dne St 26. května 2010 15:46:21 Yegor Yefremov napsal(a):
> >     I'm resurrecting an old thread
> > 
> > (http://lists.arm.linux.org.uk/lurker/message/20090914.072902.97115112.en
> > .html) about using the two memory banks available
> > on Atmel AT91SAM9G45/M10. I managed to make it work on 2.6.30 by
> > following Russell King advice on how to configure SPARSEMEM.
> > 
> >     I submitted a working patch for 2.6.34 here:
> > http://www.arm.linux.org.uk/developer/patches/viewpatch.php?id=6143/1
> > 
> > The problem is that I'm unsure how to get rid of the #define that
> > forces high_memory value in mm/init.c, should I add a fixup function
> > to board-sam9m10g45ek.c to provide meminfo information ?
> 
> I've already tested the patch on 2.6.33 and it is working properly.
> Concerning high_memory value problem I think the cause is how
> find_node_limits() in arch/arm/m/init.c is implemented. We have two memory
> banks one starting at 0x70000000 and another at 0x200000000. The virtual
> mapping looks like this:
> 
> 0x70000000 -> 0xc0000000
> 0x20000000 -> 0xc8000000
> 
> However find_node_limits() routine is working with physical addresses so
> the upper limit is 0x70000000 and not 0x20000000 as it should be. As a
> result max_low is pointing to 0x70000000 and that's why only first bank
> will be mapped correctly.
> 
> How can find_node_limits() be changed to work with virtual addresses?
> 
> Regards,
> Yegor
> 
Hey, try searching for "[PATCH 1/5] pxa/vpac270: Enable SparseMEM for 256 MB of 
RAM" ... The device has also one memory bank mapped under the primary one. Maybe 
that can help. Cheers
> 
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