On Wed, Feb 26, 2020 at 12:29:55PM +0100, Lukasz Majewski wrote: > This patch aims to improve robustness of 'usb' command operation on the > ehci-hcd IP block as it ports to contemporary U-Boot the patch described > and provided in [1] (originally applicable to U-Boot 2016.05). > > According to the fix author - "rayvt" (from [1]): > > TD stands for "Queue Element Transfer Descriptor (qTD)", which is a micro-code > instruction for the EHCI USB chip. > The "token" field is detailed information, control, and status of the TD's > data > transfer. In particular, the rightmost byte is the status field. 0x80 bit > means > the TD is active and the data transfer has not yet completed. 0x08 bit means > there was some sort of data transfer error (XactErr). > > If the drive gets a transfer error, it refuses to do any other I/O transfer > until the error is properly cleared and reset. U-boot did not do this, so > every > subsequent disk read would get a timeout error because the drive would not > send > any data. The fix is to properly clear and reset the USB disk when it gets a > transfer error. > > Every read operation starts at the maximum block size. When the USB pendrive > is > not able to correctly serve this data read request, the dynamic reduction of > IO > size is performed. Up to six tries (with smaller IO block each time) are > attempted. > > A related problem is that some drives are slow to come up. Linux handles this > by > issuing a spinup command and allowing more time for the drive to respond. The > same idea is applied in this fix. > > On TPC70 (i.MX6Q) once per ~10 times (without this patch): > > Bus usb@2184200: USB EHCI 1.00 > scanning bus usb@2184200 for devices... 2 USB Device(s) found > scanning usb for storage devices... 1 Storage Device(s) found > EHCI timed out on TD - token=0x1f8c80 > > Performance impact: > > With U-Boot -master in mainline: > 16869440 bytes read in 979 ms (16.4 MiB/s) > > With this patch: > 16869440 bytes read in 1219 ms (13.2 MiB/s) > > Links: > [1] - https://forum.doozan.com/read.php?3,35295,35295#msg-35295 > [2] - > https://www.dropbox.com/s/nrkrd1no63viuu8/uboot-bodhi-2016.05-timeoutTD.patch?dl=0 > > Signed-off-by: Lukasz Majewski <lu...@denx.de> > [Unfortunately, the original patch [2] did not contain S-o-B from the original > author - "rayvt"]
This problem was seen in Beagleboard xM as well and reported by Guillaume back in January, so: Reported-by: Guillaume Gardet <guillaume.gar...@arm.com> And on board, I can confirm the problem also goes away now so: Tested-by: Tom Rini <tr...@konsulko.com> -- Tom
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