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Date: Sat, 01 Oct 2011 19:10:48 +0100
From: Ian Jeffray <ian@emobix.co.uk>
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To: Christian Lamparter <chunkeey@googlemail.com>
CC: Larry Finger <Larry.Finger@lwfinger.net>,
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Subject: Re: r8712u driver - on ARM
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On 01/10/2011 19:01, Christian Lamparter wrote:
> On Saturday 01 October 2011 19:52:37 Larry Finger wrote:
>> On 10/01/2011 11:22 AM, Christian Lamparter wrote:
>>> On Saturday 01 October 2011 18:01:08 Larry Finger wrote:
>>>> Ian,
>>>>
>>>> Most of the skb assignments in r8712u are aligned OK and most aligned on
>>>> 512-byte boundaries, but there was one that had the minimal offset of 14 bytes.
>>>> The attached patch should fix it. Does it help?
>>> Interesting, this "patch" goes in a completely different direction.
>>> Can you tell me where the driver aligns the frames which will be
>>> xmitted by the device [i.e.: which is passed to the usb subsystem
>>> by usb_submit_urb]? Because that's what actually matters.
>>
>> In this driver, all references are to _usb_submit_urb(), which is defined to be
>> usb_submit_urb() in one of the header files. That made it easy to insert a test
>> for misalignment of the DMA buffer as follows:

<snip>

>> +static inline int _usb_submit_urb(struct urb *urb, gfp_t mem_flags)
>> +{
>> +       if (urb->transfer_dma&  3) {

<snip>

> I think you need to check transfer_buffer and not transfer_dma.

I tried checking both transfer_buffer and transfer_dma and all
were always word aligned.  (At least on Blackfin)

Ian.

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