> -----Original Message----- > From: David Brownell [mailto:[email protected]] > Sent: Thursday, June 11, 2009 3:18 PM > To: Tivy, Robert > Cc: [email protected]; Andrea Gasparini > Subject: Re: EDMA with user provided virtual addresses. > > On Thursday 11 June 2009, Tivy, Robert wrote: > > > That kind of logic is easy to wrap in utility functions. > > > (If it were wrapped, would non-DSP code really need CMEM?) > > > > ... the requirement for phys contig buffers is mostly for HW > > accelerators that address memory w/o the benefit of an MMU > or without > > chaining capability. > > (You mean "... *and* without chaining" yes? If either tech > is available, there is no "hard" requirement.)
Yes, if the bus master has *neither* an MMU nor block-chaining, phys contig bufs are needed. > > For completeness: which accelerators are those? I'm not sure of the specifics of each one, but I was thinking of coprocessors such as IMX/VICP/HDVICP/MJCP/etc. > > I expect it might be quite painful to update DSP code to > change assumptions like "physically contiguous buffers", but > on the flip side of things it seems like such changes should > probably be assumed for all mainstream Linux code that's got > to take buffers from userspace. Some codecs probably don't have a choice but to require phsyically contiguous buffers, if for no other reason than to guarantee stated performance, and to maximize throughput to allow as many instances as possible on a single system. But I'm not familiar with codecs, just heard through the grapevine. - Rob _______________________________________________ Davinci-linux-open-source mailing list [email protected] http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
