linux-kernel - Re: [PATCH v2 1/1] usb: xhci: fix checking ep busy for CFC

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Date:	Thu, 29 Oct 2015 20:58:33 +0800
From:	"Lu, Baolu" <baolu.lu@...ux.intel.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] usb: xhci: fix checking ep busy for CFC



On 10/29/2015 08:51 PM, Sergei Shtylyov wrote:
> Hello.
>
> On 10/29/2015 5:46 AM, 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@...edia.com.tw>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>>
>> ---
>> v1->v2:
>> Implement the logic in xhci_queue_isoc_tx_prepare() instead of
>> a seperated function as suggested by Mathias.
>>
>> ---
>>   drivers/usb/host/xhci-ring.c | 32 ++++++--------------------------
>>   1 file changed, 6 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
>> index fa83625..8edc286 100644
>> --- a/drivers/usb/host/xhci-ring.c
>> +++ b/drivers/usb/host/xhci-ring.c
> [...]
>> @@ -3983,10 +3961,12 @@ int xhci_queue_isoc_tx_prepare(struct 
>> xhci_hcd *xhci, gfp_t mem_flags,
>>       }
>>
>>       /* Calculate the start frame and put it in urb->start_frame. */
>> -    if (HCC_CFC(xhci->hcc_params) &&
>> -            ep_ring_is_processing(xhci, slot_id, ep_index)) {
>> -        urb->start_frame = xep->next_frame_id;
>> -        goto skip_start_over;
>> +    if (HCC_CFC(xhci->hcc_params)) {
>> +        if ((le32_to_cpu(ep_ctx->ep_info) & EP_STATE_MASK)
>> +                    == EP_STATE_RUNNING &&
>> +                !list_empty(&ep_ring->td_list))
>> +            urb->start_frame = xep->next_frame_id;
>> +            goto skip_start_over;
>
>    Forgot {}?

Oh, I am sorry. I am wondering how it passed my test.

I will send v3 patch soon any way.

>
>>       }
>>
>>       start_frame = readl(&xhci->run_regs->microframe_index);
>
> MBR, Sergei
>
> -- 
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