AW: PowerPC PCI DMA issues (prefetch/coherency?)

Chris Pringle chris.pringle at oxtel.com
Mon Jun 29 18:11:12 EST 2009


Hi Sergej,

I've attached the patch used to fix this issue. Both the patch to 
pgtable32.h and head_32.S are required in order to make it work. The 
change to pgtable32.h ensures that all pages are marked cache coherent 
(results in setting the M bit). The change to head_32.S ensures that the 
M bit is not unconditionally masked out - it should only be masked out 
if CPU_FTR_NEED_COHERENT is not set.

Hope this helps.

Cheers,
Chris

Sergej.Stepanov at ids.de wrote:
>> The other part of the fix is in asm-powerpc/pgtable32.h. _PAGE_BASE
>> needs _PAGE_COHERENT in order to work correctly, and in fact there is
>> now a comment in there to that affect in 2.6.29. Backporting that change
>> has made it work on 2.6.26. Both this patch, and the fix to head_32.S
>> are needed for it to work correctly on older kernels.
>>
>> Chris
>>     
>
> Hello Chris,
>
> sorry for dummy, but if it possible, could you, please, send a corresponding summary patch of backporting you've done for older kernels?
> or just summary of that changes once again?
>
> Many thanks
>
> Sergej.


-- 

______________________________
Chris Pringle
Software Engineer

Miranda Technologies Ltd.
Hithercroft Road
Wallingford
Oxfordshire OX10 9DG
UK

Tel. +44 1491 820206
Fax. +44 1491 820001
www.miranda.com


____________________________

Miranda Technologies Limited
Registered in England and Wales CN 02017053
Registered Office: James House, Mere Park, Dedmere Road, Marlow, Bucks, SL7 1FJ
-------------- next part --------------
A non-text attachment was scrubbed...
Name: dma-cache-coherency-fix.patch
Type: text/x-patch
Size: 2590 bytes
Desc: not available
URL: <http://lists.ozlabs.org/pipermail/linuxppc-dev/attachments/20090629/5c57286f/attachment.bin>


More information about the Linuxppc-dev mailing list