Re: EHCI software retries break Supermicro IPKVM

From: Alan Stern
Date: Thu Apr 19 2012 - 13:40:15 EST


On Thu, 19 Apr 2012, Grzegorz Nosek wrote:

> Hi,
>
> (Supermicro support: cc'd as you might be interested)
>
> Commit a2c2706e1043c17139c2dafd171c4a5cf008ef7e introduced software
> retries for transient USB errors. Unfortunately, it turns out that
> this change breaks the Supermicro AOC SIMSO IPKVM board plugged into
> a SYS-6015B-3R server, X7DBR-3 board. It renders unusable both the
> keyboard and media redirection as soon as the kernel boots (display
> works fine). An excerpt from dmesg:
>
> [ 76.587521] ehci_hcd 0000:00:1d.7: detected XactErr len 0/8 retry 1
...
> [ 76.591264] ehci_hcd 0000:00:1d.7: detected XactErr len 0/8 retry 31
> [ 76.591388] ehci_hcd 0000:00:1d.7: devpath 7 ep0out 3strikes
> [ 76.591402] usb 1-7: can't set config #1, error -71
> [ 76.596519] drivers/usb/core/inode.c: creating file '007'
> [ 76.596542] hub 1-0:1.0: state 7 ports 8 chg 0000 evt fe80
>
> After disarming the retry logic with the patch below, the KVM works
> fine again. Now, this is certainly a crude hack but apparently some
> better checks are needed to determine whether to retry the
> transaction.

Do you have any idea what's going wrong?

Can you provide complete dmesg logs for kernels both with and without
your patch (and with CONFIG_USB_DEBUG enabled)? Maybe also usbmon
traces too.

Alan Stern

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