2012/3/23 Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>:
> On Thu, Mar 22, 2012 at 11:13:00AM +0800, Elric Fu wrote:
>> When the Seagate Goflex USB3.0 device is attached to VIA xHCI
>> host, sometimes the device will downgrade mode to high speed.
>> By the USB analyzer, I found the device finished the link
>> training process and worked at superspeed mode. But the device
>> descriptor got from the device shows the device works at 2.1.
>> It is very strange and seems like the device controller of
>> Seagate Goflex has a little confusion.
>>
>> The first 8 bytes of device descriptor should be:
>> 12 01 00 03 00 00 00 09
>>
>> But the first 8 bytes of wrong device descriptor are:
>> 12 01 10 02 00 00 00 40
>>
>> The wrong device descriptor caused the initialization of mass
>> storage failed. After a while, the device would be recognized
>> as a high speed device and works fine.
>>
>> This patch will warm reset the device to fix the issue after
>> finding the bcdUSB field of device descriptor isn't 0x0300
>> but the speed mode of device is superspeed.
>
> At first I thought you missed Andiry's comment:
>
>> > + if ((udev->speed == USB_SPEED_SUPER) &&
>> > + (udev->descriptor.bcdUSB != 0x0300)) {
>>
>> Perhaps using "< 0x0300" is better.
>> Maybe there will be 3.01, 3.10 devices in the future.
>
> But now I see you just shifted it:
>
>> + if ((udev->speed == USB_SPEED_SUPER) &&
>> + (le16_to_cpu(udev->descriptor.bcdUSB) >> 8 != 0x03)) {
>
> IMO the bit shift is more difficult to understand quickly, so please use
> < 0x0300 instead. Sorry for the churn for such a simple patch, but if I
> flubbed up on understanding it, it's likely other folks will as well.
>
> Also, it's possible that we'll have SuperSpeed devices that work at
> higher speeds, so perhaps they'll have a "USB 4.0" BCD. Or perhaps USB
> 4.0 devices will show up as USB 3.0 devices under an xHCI host. In that
> case, it will be perfectly legal to have the bcdUSB show up as 0x0400,
> just like USB 3.0 devices will have a bcdUSB of 0x0300 when plugged into
> an EHCI controller. In short, please use < 0x0300 in your test.
Yes, I just thought maybe we have a USB 4.0 in future. And we will have
to modify it again.
I have tested the USB 3.0 device when it downgrade mode to high speed.
The bcdUSB of device descriptor is 0x0210. I think the device controller
should self-adjust the device descriptor. I am confused about "USB 3.0
devices will have a bcdUSB of 0x0300 when plugged into an EHCI
controller". Does It mean that even if the usb 3.0 device plugged into an
EHCI/UHCI controller the bcdUSB is always 0x3000? If yes, you will be
right and the "< 0x0300" is better than the bit shift.
Best Regards,
Elric Fu
>
> Sarah Sharp
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