On Wed, Aug 21, 2013 at 11:07:49AM -0700, Simon Gornall wrote: > >> I was hoping there was a "we changed it because..." reason. If you > >> were unaware of the problem, I guess there's little you can do to fix > >> it :) > >> > >> I'm not sure if this helps, but the driver they're talking about is > >> the D2XX driver. Apparently this is needed to put the device into > >> synchronous FIFO mode. > > > > I don't see a "d2xx" driver in the kernel source tree, where can this > > driver be found? > > http://www.ftdichip.com/Drivers/D2XX.htm > > The D2XX drivers allow you to program the EEPROM that lives alongside > the FT232H, thereby enabling synchronous FIFO mode, as well as setting > some registers within the chip to instruct it to move over to > synchronous FIFO mode. Both of these need to happen before the > sync-fifo mode is enabled, and without this, the throughput is only > guaranteed to be ~10MBytes per second on any OS. That's a userspace library, using libusb/usbfs, there's no kernel driver there, which is interesting. It would be nice to find out why things are slowing down, as I have not heard of any other slowdowns that we caused so long ago with the usbfs code. If we dropped speeds that bad, I'm guessing that someone would have told us by now, so perhaps they are doing something really strange in their code. Good luck with testing, greg k-h -- 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
