On Tue, 11 May 2010 10:24:40 -0400 Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote: > > > > Either the data isn't getting written to the buffer correctly or else > > > > the buffer isn't getting sent to the device correctly. Can anybody > > > > suggest a means of determining which is the case? > > > > > > I can't say anything about this log that including only DMA addresses. > > > I'm not familiar with how the USB core does DMA stuff. And the USB > > > stack design that the USB core does DMA stuff (allocating, mappings, > > > etc) makes debugging DMA issues really difficult. > > > > The DMA stuff is simple enough in this case. The urb->transfer_buffer > > address is passed to dma_map_single(), and the DMA address it returns > > is stored in urb->transfer_dma. Those are the two values printed out > > by the debugging patch. > > Is that address (urb->transfer_dma) the same as 'virt_to_phys(urb->transfer_buffer)' > (if not, then SWIOTLB is being utilized) and is the dma_sync_* done on the > urb->transfer_dma (to properly sync the data from the SWIOTLB to the > transfer_buffer) before you start using the urb->transfer_buffer? Or calling dma_unmap_single. Can you tell me all the exact process of DMA that the usb core and the driver do? _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
