[U-Boot] [PATCH] usb: xhci: Limit transfer length in a single TD

[Marek Vasut]

On 11/22/2016 03:42 AM, Dongwoo Lee wrote:
> On 2016년 11월 18일 23:01, Marek Vasut wrote:
>> On 11/18/2016 08:24 AM, Jaehoon Chung wrote:
>>> Hi,
>>>
>>> Added Marek as USB maintainer.
>>>
>>> On 11/17/2016 01:21 PM, Dongwoo Lee wrote:
>>>> The transfer request exceeding 4032KB (the maximum number of TRBs per
>>>> TD * the maximum size of transfer buffer on TRB) fails on xhci host
>>>> with timed out error or babble error state. This failure occurs when
>>>> accessing large files on USB mass-storage. Currently with xhci as well
>>>> as ehci host, the driver requests maximum 30MB (65536 blks * 512 byte)
>>>> to storage at once. However, xhci cannot handle this request because
>>>> of the reason mentioned above, even though ehci can handle this. Thus,
>>>> transfer request larger than this size should be splitted in order to
>>>> limit the length of data in a single TD.
>>>>
>>>> Even though the single request is splitted into multiple requests,
>>>> the transfer speed has affected insignificantly in comparison with
>>>> ehci host: 22.6 MB/s on ehci and 22.3 MB/s on xhci for 100MB tranfer.
>>>
>>> I don't have USB knowledge..So i wonder that this is correct way.
>>> Have other guys ever seen the similar issue?
>>
>> Is this a controller limitation ?
>>
>> btw can you fix your mailer to NOT send HTML email to the list?
>>
> 
> If my understanding for xhci spec.(rev. 1.1) 4.9.2 is right, the controller 
> has no limitation for transfer size because it can support a very large TRB 
> ring with multiple Ring Segments. 
> 
> However, the xhci driver seems not to be implemented for supporting it; 
> the TRB ring is comprised of only a single segment. As a result, it cannot 
> handle the request exceeding 4032KB (TRB_MAX_BUFF_SIZE(64KB) * 
> (TRBS_PER_SEGMENT(64) - link TRB(1)), thus the request should be divided.  

Can we update the driver ?

> This issue can be reproduced by using the following command on Odroid-XU3/XU4
> with USB mass-storage connected to xhci host:
> 
> 	>fatload usb 0 40800000 {a file exceeding 4032KB}
> 
> About HTML email, I just mailed with git-send-email, but I will double-check 
> the setting.

OK

-- 
Best regards,
Marek Vasut