On Tue, Nov 20, 2012 at 05:07:59PM +0000, Thomas Petazzoni wrote: > Dear Will Deacon, > > On Tue, 20 Nov 2012 17:01:27 +0000, Will Deacon wrote: > > > > I prefer to keep them separate, as we can use coherency without SMP. > > > That's why I create the coherency_ll.S file instead of putting > > > everything in this file. > > > > Hmm, can you elaborate a bit more on coherency without SMP please? Do > > these controls also affect IO coherency? > > The coherency unit does coherency between CPUs, but also between the > CPU and the devices for DMA. So for example the MV78230 is a single-core > variant of the Armada XP, so having CONFIG_SMP for it is useless, but > you still want the CPU to join the coherency fabric in order to provide > coherency with I/O. > > Thanks to the coherency unit, we have an almost DMA coherent > architecture (see the HW I/O coherency patches from Grégory for > details).
Ok, gotcha -- I didn't realise it was all controlled by the same register on the CPU side. Thanks for the explanation, Will _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
