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

[Marek Vasut]

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?

-- 
Best regards,
Marek Vasut