On 11/24/2013 09:15 PM, Benjamin Herrenschmidt wrote: > On Fri, 2013-11-08 at 11:43 -0200, Kleber Sacilotto de Souza wrote: >> On 11/07/2013 08:29 PM, Benjamin Herrenschmidt wrote: >>> On Mon, 2013-06-17 at 18:57 -0400, Alex Deucher wrote: >>> >>>> Weird. I wonder if there is an issue with cache snoops on PPC. We >>>> currently use the gart in cached mode (GPU snoops CPU cache) with >>>> cached pages. I wonder if we need to use uncached pages on PPC. >>> There is no such issue and no known bugs with DMA writes on those >>> PCIe host bridges (and they do get hammered pretty bad here). >>> >>> This needs further investigation by the lab/hw guys to find out what's >>> actually happening on the bus and the host bridge. >>> >>> Thadeu, Kleber: Jerome suggested writing a test case in userspace that >>> continuously writes to a spare scratch register (thus triggering the >>> corresponding writeback DMA) and checks the memory location to compare >>> the writeback value (using a debugfs file for example, or mmap). >>> >> I can look into that. > Any news ? Only now I've got the bandwidth to actually take a look at this. I will start to write some code and let you guys know of the results.
Thanks, Kleber > > Ben. > >> Thanks, >> >> Kleber >> >>> Can you guys do something like that ? Then we need the analyzer on >>> and/or the lab guys to look at the fabric trace & PHB trace. >>> >>> Ben. >>> >>> >> > -- Kleber Sacilotto de Souza IBM Linux Technology Center
