Hi list. I have several sensor boards connected to PC via UART, actually an FTDI FT4232H quad port USB 2.0 to UART bridge in-between. With sensor board A: baud: 115200 bps, actual transfer: 320 Bps, there is no problem whether or not ehci high speed mode is enabled. With sensor board B: baud: 115200 bps, actual transfer: 6400 Bps, there is still no problem when high speed mode is disabled. However when high speed mode is enabled, a program waits read() to complete for a long time or even forever. Tried using a USB 2.0 hub and no luck. With hw.usb.debug and hw.usb.ehci.debug tunables both set to 1 and I got many USB_ERR_STALLED errors. The machine runs yesterday's 8.0-STABLE amd64. Is there a way to fix/diagnose the problem? Thanks. -- UEMURA Tetsuya <t_uemura@macome.co.jp> -------------- next part -------------- A non-text attachment was scrubbed... Name: dmesg.txt Type: application/octet-stream Size: 11868 bytes Desc: not available Url : http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20091128/73324774/dmesg-0001.obj -------------- next part -------------- A non-text attachment was scrubbed... Name: usb-log.txt Type: application/octet-stream Size: 91895 bytes Desc: not available Url : http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20091128/73324774/usb-log-0001.obj