From: Thomas Petazzoni > Sent: 07 March 2017 18:12 > Hello, > > On Tue, 7 Mar 2017 17:24:21 +0000, David Laight wrote: > > > Are the coherent mappings just used for ring structures? > > If it might be reasonable to allocate them as a single entity, > > thus guaranteeing they all reside in a single 4G region. > > Do we have the guarantee that a DMA coherent allocation will not span a > 4G boundary?
I'm pretty sure they are guaranteed not to cross any boundary they don't have to. So a 16k buffer won't cross a 16k boundary. David