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.
Sarah Sharp
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