On 3/2/20 8:54 PM, Tom Rini wrote: > On Mon, Mar 02, 2020 at 08:19:22PM +0100, Marek Vasut wrote: >> On 3/2/20 2:21 PM, Lukasz Majewski wrote: >>> Hi, >> >> Hi, >> >>>> 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). >>> ^^^^^^^ - this error is NOT handled now in mainline u-boot. Do >>> you have any experience with it? >> >> No, but then I also didn't run into those yet. >> >>>> 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. >> >> So basically, what this says is, "we crashed the drive, because the >> drive suffered counter overflow, thus we fix it by resetting the drive". >> No, the fix is to not crash the drive in the first place. >> >>>> 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 >>> >>> This is how the error gets evident. The detailed explanation is in link >>> [1]. >> >> Is there one specific post in that forum, or do I need to read through >> the whole multi-page thread ? >> >> I would expect that if you run -- I assume 'usb reset' (the command is >> missing above) -- then the bus gets power-cycled, hence the USB device >> also gets power-cycled. > > FWIW, the problem I have does not get fixed via "usb reset". Ethernet > never shows up again. I do see right now that I disabled network tests > on the platform a long while ago for unknown reasons, but did comment to > myself elsewhere that network was fairly flaky in U-Boot.
There certainly is something with USB ethernet in U-Boot. I noticed the flakiness myself, but didn't have time to investigate. Patches welcome I guess ?