Re: [PATCH 2/2] usb: dwc2: fix isoc split in transfer with no data

From: wlf <wulf@rock-chips.com>
To: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
	William Wu <william.wu@rock-chips.com>,
	hminas@synopsys.com, felipe.balbi@linux.intel.com,
	gregkh@linuxfoundation.org
Cc: heiko@sntech.de, linux-kernel@vger.kernel.org,
	linux-usb@vger.kernel.org, linux-rockchip@lists.infradead.org,
	frank.wang@rock-chips.com, huangtao@rock-chips.com,
	dianders@google.com, daniel.meng@rock-chips.com,
	John.Youn@synopsys.com, wzz@rock-chips.com, zsq@rock-chips.com,
	Allen.Hsu@quantatw.com, StanTsui@AOPEN.com
Subject: Re: [PATCH 2/2] usb: dwc2: fix isoc split in transfer with no data
Date: Tue, 24 Apr 2018 17:04:26 +0800	[thread overview]
Message-ID: <4daa0026-f5b5-a82f-08b1-20196968dcfb@rock-chips.com> (raw)
In-Reply-To: <799e2eea-be83-b3c1-3ee7-7a66b1759379@cogentembedded.com>

Dear Sergei,

在 2018年04月24日 16:27, Sergei Shtylyov 写道:
> Hello!
>
> On 4/24/2018 5:43 AM, William Wu wrote:
>
>> If isoc split in transfer with no data (the length of DATA0
>> packet is 0), we can't simply return immediately. Because the
>> DATA0 can be the first transaction or the second transaction for
>> the isoc split in transaction. If the DATA0 packet with on data
>                                                           ^^ no?
Thank you for correcting me. I will fix it in next patch version.
>
>> is in the first transaction, we can return immediately. But if
>> the the DATA0 packet with on data is in the second transaction
>
>   One "the" too many. And that "on data" again... :-)
Ah, sorry to make such a simple mistake. I will fix these in next patch 
version.
>
>> of isoc split in transaction sequence, we need to increase the
>> qtd->isoc_frame_index and giveback urb to device driver if needed,
>> otherwise, the MDATA packet will be lost.
>>
>> A typical test case is that connect the dwc2 controller with an
>> usb hs Hub (GL852G-12), and plug an usb fs audio device (Plantronics
>> headset) into the downstream port of Hub. Then use the usb mic
>> to record, we can find noise when playback.
>>
>> In the case, the isoc split in transaction sequence like this:
>>
>> - SSPLIT IN transaction
>> - CSPLIT IN transaction
>>    - MDATA packet (176 bytes)
>> - CSPLIT IN transaction
>>    - DATA0 packet (0 byte)
>>
>> This patch use both the length of DATA0 and qtd->isoc_split_offset
>> to check if the DATA0 is in the second transaction.
>>
>> Signed-off-by: William Wu <william.wu@rock-chips.com>
> [...]
>
> MBR, Sergei
Best regards,
     wulf
>
>
>