Sarah Sharp wrote:
When an endpoint on a device under an xHCI host controller stalls, the
host controller driver must let the hardware know that the USB core has
successfully cleared the halt condition. The HCD submits a Reset Endpoint
Command, which will clear the toggle bit for USB 2.0 devices, and set the
sequence number to zero for USB 3.0 devices.
The xHCI urb_enqueue will accept new URBs while the endpoint is halted,
and will queue them to the hardware rings.
Just out of curiosity,
Is there any possibility of hardware ring overflow and thus loss of
data, while endpoint is halted ?
This could be irrelevant but I was not able to get anything by looking
at the source.
However, the endpoint doorbell
will not be rung until the Reset Endpoint Command completes.
Don't queue a reset endpoint command for root hubs. khubd clears halt
conditions on the roothub during the initialization process, but the roothub
isn't a real device, so the xHCI host controller doesn't need to know about the
cleared halt.
--
Thanks, Viral Mehta, Embedded Software Engineer, Tel. No. 91 79
26563705, Ext. 423 www.einfochips.com
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