Re: HC died

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 17.2.2023 16.21, Seth Bollinger wrote:
> Hello All,
> 
> We're experiencing a problem with our devices in the field where our
> customers attach problematic USB devices that are causing the xhci
> host controller to shut down with the "HC died; cleaning up" message.

Is this seen only on some specific xHC host controller?

> 
> I've narrowed this down to a timeout of the address device TRB on the
> command ring (currently 5 seconds).  It sometimes takes our hardware
> 9.6 to complete this TRB.  When the driver is trying to stop the cmd
> ring, the controller is busy for an additional 4.6 seconds.  This
> results in the "HC died" message and shutdown of the host controller.
> 
> If I bump the command ring timeout beyond the max TRB completion time,
> the host controller continues to be responsive and doesn't need to be
> shut down.
> 
> My knowledge of how the usb protocol should handle this problem isn't
> strong enough to know if there is a better solution than simply
> increasing the command ring default timeout.

Are these problematic devices USB 2 or USB 3 devices?

You could try playing with the Address device command BSR (block set
address request) flag and see if helps.
Xhci has two ways to get a slot from the Enabled to the Addressed state.

option 1: move slot from Enabled state to Addressed in one go:
Enabled --(Addr dev cmd, BSR=0)--> Addressed

option 2: move from Enabled state via Default state to Addressed state:
Enabled --(Addr dev cmd, BSR=1)--> Default --(Addr dev cmd, BSR=0)--> Addressed

I think the usb core "old_scheme_first" module parameter will end up doing this.

-Mathias