So I just did a very quick test where I read 100000 an ADC snapshot (8192 Bytes) via mmap(boost::iostreams::mapped_file) using std::copy(). This took about 52 seconds which is about 15MB/s or 120Mb/s - Sound to fast???
Ross On Wed, Oct 16, 2013 at 11:47 AM, Ross Williamson <rwilliam...@astro.caltech.edu> wrote: > Hi Guys, > > Thanks - I'm initially going to pursue the mmap option. I > think quite a few of the issues are tcp latencies and by removing > those I can make the link more reliable. I'm looking at a max of > about 5Mb/s through the FPGA-->PPC interface. I should fairly soon be > able to check what speed I can achieve. > > Ross > > On Wed, Oct 16, 2013 at 11:26 AM, David Hawkins <d...@ovro.caltech.edu> wrote: >> Hi Dave, >> >> >>>> Boot the board, stop in U-Boot, write to the DMA registers >>>> directly, and probe the bus to see what the maximum rate possible >>>> is ... then you can decide whether to write a device driver to use >>>> the DMA controller under Linux. >>> >>> >>> Oh, yeah, trying to use the DMA controllers on the PPC side would be >>> very interesting! I was referring to the CASPER implementation of >>> the FPGA side of the EPB bus not supporting being a DMA bus master >>> (I'm not even sure that the EPB bus supports external DMA bus >>> masters). >> >> >> The 440EP and the Freescale processors do not support external >> DMA masters ... in fact, I'm not sure that I have seen any >> recent processor that supports this feature (I've looked at >> many ARM-based processor data sheets). Although I think its >> a common feature on DSP processors ... >> >> >>>> If Ross has never had to do this before, he might not have >>>> appreciated where to look/where to start. >>> >>> >>> If Ross has never had to do this before, he's probably better off >>> using the pre-canned "Ethernet directly from the FPGA" solution >>> rather than (re-)writing a Linux device driver to use DMA. :-) >> >> >> Sure, I was just adding to his list of options :) >> >> Cheers, >> Dave >> >> > > > > -- > Ross Williamson > Research Scientist - Sub-mm Group > California Institute of Technology > 626-395-2647 (office) > 312-504-3051 (Cell) -- Ross Williamson Research Scientist - Sub-mm Group California Institute of Technology 626-395-2647 (office) 312-504-3051 (Cell)
