Hi, Claus Stovgaard <claus.stovgaard@xxxxxxxxx> writes: > On tir, 2020-05-12 at 15:52 -0400, Alan Stern wrote: >> On Tue, May 12, 2020 at 09:25:38PM +0200, Claus Stovgaard wrote: >> > >> > In a certain scenario I would like to force the dwc3 to only >> > connect >> > via superspeed and not fall back to USB2. >> > >> > What options exist for forcing the dwc3 to keep retry? >> >> The USB-3 spec forbids devices from operating only at SuperSpeed. >> Devices must be able to connect at high speed, although possibly >> with >> reduced functionality. >> >> Alan Stern >> > > I understand the requirement from the USB 3 specification. Though in > the scenario for this specific device, it is not about comply with the > USB 3 specification, but my question is rather what options I have for > not comply with the specification here, and then force retry of USB 3, > using the dwc3 as device. > > The device is in a fixed mounting with a fixed host. Sometimes when the > host and device is powered up, it ends in high-speed instead of super- > speed. I would like the option for "I will not be compliant with USB, > but rather retry super-speed". If it's "ending in super-speed" this means it tried RX.Detect and it failed, thus falling back to high-speed. It's likely that the signal quality in your setup has degraded or is, at least, sub-par. Forcing a SS-only setup would just give you a device that doesn't even enumerate in some cases. Could you capture dwc3 tracepoints of the problem? Also, which kernel version are you running? Which platform? best -- balbi
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