On Fri, Mar 23, 2012 at 10:00:38AM +0800, Elric Fu wrote: > 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. Sorry, I had that backwards. USB 3.0 devices always show up as bcdUSB 0x0201 on EHCI or UHCI host controllers: http://marc.info/?l=linux-usb&m=132632097124520&w=2 However, I still think that the "< 0x0300" is easier to understand, so please use that. Sarah Sharp -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html