On Mon, Feb 22, 2016 at 2:51 PM, Maxime Jayat <jayatmax...@gmail.com> wrote:
> Hello, > I was hit by the same problem, where my USB SD card reader would timeout > in U-boot when reading a large file (16 MB). Changing USB_MAX_XFER_BLK > to 32767 fixed the problem but I investigated a little more. > I was curious to see what the Linux kernel used, because it had no > problem reading the file. In Linux, USB_MAX_XFER_BLK corresponds to > max_sector in the scsiglue, which is set to 240 blocks per transfer by > default, and is tunable via sysfs. > There is also a list of unusual devices which needs no higher than 64 > blocks per transfer. > The linux USB FAQ has a very interesting entry about this which explains > the rationale for this value: > http://www.linux-usb.org/FAQ.html#i5 > > FWIW: my USB card reader is > 0bda:0119 Realtek Semiconductor Corp. Storage Device (SD card reader) > > I've benchmarked in U-boot the time impact of this change. > For reading my 16764395 bytes file: > USB_MAX_XFER_BLK Read duration (as reported by U-boot): > 64 3578 ms > 128 2221 ms > 240 1673 ms > 32767 1020 ms > 65535 974 ms > > So there is definitely a strong impact for lower values. Ok, so with a USB_MAX_XFER_BLK size of 32767 there is not so much of a performance impact. Looks like that changing USB_MAX_XFER_BLK from 65535 to 32767 is the way to go. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot