I'll add a few more details since you seem to be somewhat interested in our specific application. The HP DL120 server has an EHCI-only HCD, which connects to an embedded USB 2.0 hub chip on the motherboard itself. There is no OHCI nor UHCI companion controller as far as I can tell. USB physical ports connect via motherboard traces from that embedded hub to the USB type-A sockets on the front and rear of the chassis, and also to an internal USB header. The internal header is intended for use with fixed USB storage modules. We are using an industrial-grade module similar to this one http://www.atpinc.com/p2-4a.php?sn=00000533 The signal traces on the motherboard from the embedded USB socket to the USB controller are fairly short and direct, but I noticed the USB bus traces running from the embedded hub out to the external chassis connectors pass very close to the CPU. A keyboard and mouse are connected to those external connectors on the rear of the chasiss. So I thought: maybe the problem was a physical issue with EMI or noise, and perhaps de-rating the transfer speed on those signal traces to FS could mitigate the problem. I hoped for a way to tell the HCD to do that, which is where this thread started... In terms of physical workarounds, as the USB storage module resides within the server chassis itself, there's nowhere to insert a FS hub unfortunately. So any fix or workaround is going to have to be in software. Unfortunately from Alan's responses it seems there isn't a way to slow down the HDC to BUS connection in software, as that is hard-coded at HS. I am testing now; if I can get a debug trace (the problem is very intermittent) I'll post a followup shortly. -- 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
