Re: System hangs when using USB 3.0 HD with on Ubuntu

[Sergei Shtylyov <sshtylyov@mvista.com>]

Hello.

Alan Stern wrote:

>>> Best guess (and it's a guess only) would be that the USB bridge SAT
>>> layer doesn't implement ATA_16 and so fails in interesting ways when it
>>> comes in.  Does the ATA_12 version of IDENTIFY DEVICE succeed?
>>>       
>> It does.  And in between the two is an ATA_16 SET FEATURES command
>> which also (apparently) succeeds.  That is, there is no error
>> indication from the device -- but goodness knows if it actually carries
>> out the command.
>>     
>
> Incidentally, there's a discussion of this problem with input from an
> engineer at the company that makes the bridge chip here:
>
> https://bugs.launchpad.net/ubuntu/+source/linux-fsl-imx51/+bug/431963
>
> See comment #25 and later.  He claims that the ATA pass-through command
> contains a SECTOR COUNT field of 0 even though it asks for 512 bytes of
> IDENTIFY data.  This invalid parameter combination causes the bridge
> chip to get confused, and instead of failing gracefully, it messes up
> the USB protocol.
>   

   IDENTIFY DEVICE command always returns 512 bytes of data, regardless 
of any value in the sector count register.

> Does anybody know where to find out why hdparm is sending an IDENTIFY 
> command with invalid parameters?
>   

   IDENTIFY DEVICE command has *no* parameters.

> Alan Stern
>   
WBR, Sergei