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Subject: Re: [PATCH v4 1/2] usb: dwc2: alloc dma aligned buffer for isoc split
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To:     Doug Anderson <dianders@google.com>,
        William Wu <william.wu@rock-chips.com>
Cc:     hminas@synopsys.com, felipe.balbi@linux.intel.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
        =?UTF-8?Q?Heiko_St=c3=bcbner?= <heiko@sntech.de>,
        LKML <linux-kernel@vger.kernel.org>, linux-usb@vger.kernel.org,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        Frank Wang <frank.wang@rock-chips.com>,
        =?UTF-8?B?6buE5rab?= <huangtao@rock-chips.com>,
        "daniel.meng" <daniel.meng@rock-chips.com>,
        John Youn <John.Youn@synopsys.com>,
        =?UTF-8?B?546L5b6B5aKe?= <wzz@rock-chips.com>,
        zsq@rock-chips.com,
        =?UTF-8?B?6Kix5ZiJ6YqY?= <Allen.Hsu@quantatw.com>,
        Stan Tsui <StanTsui@aopen.com>,
        =?UTF-8?B?U3BydWNlIFd1ICjlkLPlu7rli7Mp?= <Spruce.Wu@quantatw.com>,
        Martin Tsai <Martin.Tsai@quantatw.com>,
        Kevin Hsueh <Kevin.Shai@quantatw.com>,
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        <Claud.Chang@quantatw.com>,
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        Ren Kuo <Ren.Kuo@quantatw.com>,
        "David H.T. Wang" <davidhtwang@aopen.com>,
        Fong Lin <fonglin@aopen.com>,
        Steven Cheng <stevencheng@aopen.com>,
        Tom Chen <tomchen@aopen.com>, Don Chang <donchang@aopen.com>,
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From:   wlf <wulf@rock-chips.com>
Message-ID: <60703355-c0e5-f6f4-0933-1efb7b46dded@rock-chips.com>
Date:   Fri, 11 May 2018 17:33:55 +0800
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Dear Doug,

在 2018年05月11日 05:01, Doug Anderson 写道:
> Hi,
>
> On Wed, May 9, 2018 at 3:11 AM, William Wu <william.wu@rock-chips.com> wrote:
>> The commit 3bc04e28a030 ("usb: dwc2: host: Get aligned DMA in
>> a more supported way") rips out a lot of code to simply the
>> allocation of aligned DMA. However, it also introduces a new
>> issue when use isoc split in transfer.
>>
>> In my test case, I 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.
>>
>> It's because that the usb Hub uses an MDATA for the first
>> transaction and a DATA0 for the second transaction for the isoc
>> split in transaction. An typical isoc split in transaction sequence
>> like this:
>>
>> - SSPLIT IN transaction
>> - CSPLIT IN transaction
>>    - MDATA packet
>> - CSPLIT IN transaction
>>    - DATA0 packet
>>
>> The DMA address of MDATA (urb->dma) is always DWORD-aligned, but
>> the DMA address of DATA0 (urb->dma + qtd->isoc_split_offset) may
>> not be DWORD-aligned, it depends on the qtd->isoc_split_offset (the
>> length of MDATA). In my test case, the length of MDATA is usually
>> unaligned, this cause DATA0 packet transmission error.
>>
>> This patch use kmem_cache to allocate aligned DMA buf for isoc
>> split in transaction. Note that according to usb 2.0 spec, the
>> maximum data payload size is 1023 bytes for each fs isoc ep,
>> and the maximum allowable interrupt data payload size is 64 bytes
>> or less for fs interrupt ep. So we set the size of object to be
>> 1024 bytes in the kmem cache.
>>
>> Signed-off-by: William Wu <william.wu@rock-chips.com>
>> ---
>> Changes in v4:
>> - get rid of "qh->dw_align_buf_size"
>> - allocate unaligned_cache for Address DMA mode and Desc DMA mode
>> - freeing order opposite of allocation
> You only did half of this.  You changed the order under "error4" but
> forgot to make dwc2_hcd_remove() match.
Ah, sorry, I'm careless.
>
>
>> - do dma_map_single() with the size of DWC2_KMEM_UNALIGNED_BUF_SIZE
>>
>> Changes in v3:
>> - Modify the commit message
>> - Use Kmem_cache to allocate aligned DMA buf
>> - Fix coding style
>>
>> Changes in v2:
>> - None
>>
>>   drivers/usb/dwc2/core.h      |  3 ++
>>   drivers/usb/dwc2/hcd.c       | 87 ++++++++++++++++++++++++++++++++++++++++++--
>>   drivers/usb/dwc2/hcd.h       |  8 ++++
>>   drivers/usb/dwc2/hcd_intr.c  |  8 ++++
>>   drivers/usb/dwc2/hcd_queue.c |  3 ++
>>   5 files changed, 105 insertions(+), 4 deletions(-)
> My only remaining comment is a really nitty detail.  Unless someone
> else feels strongly about it, I'm not sure it's worth spinning the
> patch just for that nit unless someone else has review comments.
>
> I believe I've looked at this enough to say:
>
> Reviewed-by: Douglas Anderson <dianders@chromium.org>
Thank you very much for your review. I will submit V5 patches to fix the 
order of memory free in dwc2_hcd_remove()， and also add Review-by.
>
>
>