> -----Original Message----- > From: Russell King - ARM Linux [mailto:linux@xxxxxxxxxxxxxxxx] > Sent: Tuesday, July 27, 2010 3:31 PM > To: Shilimkar, Santosh > Cc: Mankad, Maulik Ojas; linux-usb@xxxxxxxxxxxxxxx; linux- > omap@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: Re: Issue with file transfers to a mass storage device on SMP > system > > On Tue, Jul 27, 2010 at 03:08:54PM +0530, Shilimkar, Santosh wrote: > > As discussed, the main reason is the cache maintenance isn't done on > > "bcb->CDB" buffers and hence the data remains in CPU write buffer > > instead of the physical memory on which DMA operates. > > struct bulk_cb_wrap { > __le32 Signature; /* contains 'USBC' */ > __u32 Tag; /* unique per command id */ > __le32 DataTransferLength; /* size of data */ > __u8 Flags; /* direction in bit 0 */ > __u8 Lun; /* LUN normally 0 */ > __u8 Length; /* of of the CDB */ > __u8 CDB[16]; /* max command */ > }; > > So, CDB is contained within bcb...bcb+sizeof(*bcb). > > The bcb is passed to usb_stor_bulk_transfer_buf: > > result = usb_stor_bulk_transfer_buf(us, us->send_bulk_pipe, > bcb, cbwlen, NULL); > > which fills it into a URB: > > usb_fill_bulk_urb(us->current_urb, us->pusb_dev, pipe, buf, > length, > usb_stor_blocking_completion, NULL); > > This sets the URB buffer pointers: > > urb->transfer_buffer = transfer_buffer; > urb->transfer_buffer_length = buffer_length; > > And this buffer should be dma-mapped and dma-unmapped as appropriate. > > Wasn't there an issue with the DMA mapping being used with a PIO USB > host recently? Is that the problem here? That's correct. The last issue was otherway round where we were doing map/unmpap on PIO buffer. This issue is because "CDB[16]", is not cleaned up before merging it into CBW. Regards, Santosh -- 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
