Why do we try to enter U1 mode in SuperSpeed?

[Kohji Okuno]

Hi HPS,

> On 03/30/15 06:54, Kohji Okuno wrote:
>> Hi HPS
>>
>> I have a question.
>> Why do we try to enter U1 mode in SuperSpeed?
>> This is the following codes(***)
>>
>> In our proprietary environmen(This has a xHCI controller), when a
>> device accept U1, the device may be strange status. Acutually, when I
>> tried to connect "Western Digital My Passport Essential 320GB
>> (P/N:WDBACY3200ABK-00)", this HDD was not recognized correctly.
>> But, in PC environment, this HDD was recognized correctly.
>>
>> Regards,
>>   Kohji Okuno
>>
>> (***)
>> usb_hub.c:
>> 793	        if (speed == USB_SPEED_SUPER) {
>> 794	                err = usbd_req_set_hub_u1_timeout(udev, NULL,
>> 795	                    portno, 128 - (2 * udev->depth));
>> 796	                if (err) {
>> 797	                        DPRINTFN(0, "port %d U1 timeout "
>> 798	                            "failed, error=%s\n",
>> 799	                            portno, usbd_errstr(err));
>> 800	                }
>> 801	                err = usbd_req_set_hub_u2_timeout(udev, NULL,
>> 802	                    portno, 128 - (2 * udev->depth));
>> 803	                if (err) {
>> 804	                        DPRINTFN(0, "port %d U2 timeout "
>> 805	                            "failed, error=%s\n",
>> 806	                            portno, usbd_errstr(err));
>> 807	                }
>> 808	        }
> 
> Hi,
> 
> We are not trying to enter U1 mode, we only setup the U1 and U2 timeouts. Is
> there a flag in the USB descriptors that say this is not supported and that we
> need to set some other value? I thought all superspeed devices had to support
> these features and that switching in and out of the sleep modes was done by
> the XHCI hardware.
> 
> --HPS

Thank you for your prompt response.
I understood your comment. And, I missunderstood about this.
But, in our xHCI, when we set these timeout values, its xHCI
controller sends LGO_U1 and the specified HDD accepts LGO_U1.
In this result, its HDD is not recognized correctly.
I think that our xHCI is wrong...

--
Regards,
 Kohji Okuno