Richard B. Johnson wrote: > ----- Original Message ----- From: "Mark Hounschell" <markh@xxxxxxxxxx> > To: <linux-pci@xxxxxxxxxxxxxxx> > Cc: "Mark Hounschell" <dmarkh@xxxxxxxxxx>; <linux-kernel@xxxxxxxxxxxxxxx> > Sent: Friday, September 11, 2009 10:13 AM > Subject: problems doing direct dma from a pci device to pci-e device > > >> I know this is really just a pci issue but have CC'd LKML just in >> case. Sorry LKML for the noise. >> >> I have a situation where a card on a regular PCI bus (Compro gpiohsd) >> does dma's >> directly into another PCI cards memory (VMIC-5565 reflective memory) >> living on >> another PCI bus. These 2 cards are sometimes seperated by many bridges. >> Expansion racks etc. We've been doing this forever. No problem (mostly). >> >> I now have an AM3 based DFI DK 790FXB-M3H5 motherboard. This board has >> 3 regular >> PCI slots and 3 PCI-E (16x) slots. I also have a PCI-E (x4) version of >> the VMIC-5565 >> reflective memory card in one of the PCI-E slots and our gpiohsd card >> in one of the regular >> PCI slots. All on the motherboard. No expansion slots being used. >> However I cannot get >> data from our gpiohsd into the PCI-E VMIC-5565 cards memory. I can >> certainly get the data there >> from a userland buffer, no problem. Just not from one card to the >> other directly. Oh and when >> I put the regular PCI version of the VMIC into one of the regular PCI >> slots everything works >> as expected. They are then both on the same PCI bus and no bridges are >> involved though. >> > > [SNIPPED...] > > Please check your software to make sure that after the DMA has presumed > to complete, you READ something from the destination PCI bus address! > With so many PCI writes queued, they may all be stuck in the many > hardware FIFOs and the sure way to complete the writes is to perform a > read. > Cheers, > Richard B. Johnson > http://Route495Software.com/ > > > > > Thanks, that's actually how I know the data never gets to it's destination. I read it. The data gets lost somewhere. Regards Mark -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
