Richard B. Johnson wrote: > ----- Original Message ----- From: "Mark Hounschell" <markh@xxxxxxxxxx> > To: "Alan Cox" <alan@xxxxxxxxxxxxxxxxxxx> > Cc: <linux-pci@xxxxxxxxxxxxxxx>; "Mark Hounschell" <dmarkh@xxxxxxxxxx>; > <linux-kernel@xxxxxxxxxxxxxxx> > Sent: Friday, September 11, 2009 11:25 AM > Subject: Re: problems doing direct dma from a pci device to pci-e device > > >> Alan Cox wrote: >>>> 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. > > The read I mentioned was a read immediately following the DMA operation. > Some PCI (PCI-X using > a HyperTransport serial bus) implimentations deliberately time-out to > prevent a hung system. The result > that I've seen was no data anywhere. It just vanished! > > Reading the destination a few milliseconds (or seconds) later won't > prevent this timeout! > How about a couple hundred usecs? Along that line, I can make it do dma reads from that VMIC card also. All I get is ones. It's strange that in this case, my gpiohsd isn't reporting any kind of pci bus error in it's status register. Thanks 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
