Re: [PATCH v3 1/1] usb: xhci: fix checking ep busy for CFC

From: Mathias Nyman
Date: Fri Oct 30 2015 - 08:10:38 EST

On 29.10.2015 16:24, Lu Baolu wrote:
Function ep_ring_is_processing() checks the dequeue pointer
in endpoint context to know whether an endpoint is busy with
processing TRBs. This is not correct since dequeue pointer
field in an endpoint context is only valid when the endpoint
is in Halted or Stopped states. This buggy code causes audio
noise when playing sound with USB headset connected to host
controllers which support CFC (one of xhci 1.1 features).

This patch should exist in stable kernel since v4.3.

Reported-and-tested-by: YD Tseng <yd_tseng@xxxxxxxxxxxxxx>
Signed-off-by: Lu Baolu <>
Implement the logic in xhci_queue_isoc_tx_prepare() instead of
a seperated function as suggested by Mathias.

Add the missing {} pair found by Sergei.
Adjust line for code readability as suggested by Mathias.


Added to queue with stable tag for v4.3
Will send forward once 4.4-rc1 is out


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