On Tue, Dec 13, 2016 at 5:24 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 12 Dec 2016, John Stultz wrote: > >> From: Chen Yu <chenyu56@xxxxxxxxxx> >> >> The Hi6220's usb controller is limited in that it does not >> support "Split Transactions", so it does not support communicating >> with low-speed and full-speed devices behind a high-speed hub. >> >> Thus it requires a quirk so that we can manually drop the usb >> speed when low/full-speed are attached, and bump back to high >> speed when they are removed. > > Just out of curiosity (I know nothing about this hardware), what If your interested in details, page 12 of the pdf here has some details: https://github.com/96boards/documentation/blob/master/ConsumerEdition/HiKey/AdditionalDocs/HiKey_Hardware_User_Manual_Rev0.2.pdf There's also schematics for the board available (if you are interested in that sort of stuff). You can find the USB bits on Page 4 here: https://github.com/96boards/documentation/blob/master/ConsumerEdition/HiKey/HardwareDocs/HiKey_schematics_LeMaker_version_Rev_A1.pdf > happens if there is a high-speed hub plugged into the host controller > and both a high-speed and a full-speed device plugged into the hub? > > Do you end up forcing the high-speed device to run at full speed? Yes. It drops back to full-speed. thanks -john -- 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
