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). Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
