On Thu, 7 Jul 2011, Daniel Mack wrote: > On Thu, Jul 7, 2011 at 2:33 PM, Oliver Neukum <oliver@xxxxxxxxxx> wrote: > > > PS: �Do you still see this if you enable 64bit DMA for EHCI? > > The problem is that I personally don't see that issue at all. I even > installed 4GB of RAM to my development machine last year to be able to > reproduce this, but I can't, even when the memory allocator is under > heavy load. The only people who see this effect are Pedro Ribeiro and > William Light (both in Cc:), and both have been very helpful in trying > patches and reporting back in detail. Which instructions could we > probably give to these people to finally hunt this issue down? Oliver is perfectly right; this problem needs to be solved at the source. One thing you might be able to do is put together a debugging patch that would print out the bus address corresponding to the DMA handle after the DMA mapping takes place, i.e., after the second dma_map_single() call in usb_hcd_map_urb_for_dma() returns. Or at least, check the bus address to see if it is below the 4 GB limit and print out an error message if it isn't. (I don't know how one translates a DMA address to a bus address. You'd have to ask somebody who knows or figure it out.) Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
