> > The reason is that ehci_handle_root_hub_status_change() in ehci driver is > > called once every 256 ms to poll the ehci root hub or port status change. > > The fix way is to change the polling to the interrupter-driven. Fortunately, > > there is a corresponding interrupt enable bit(Port Change Interrupt Enable) > > offered in the ehci interrupt register. It will be supported to fix the > > issue. > > This might be one of the causes. 256ms is long enough to let CPUs enter > deep package C-state. I guess there must be some other activities from USB.
The USB 1.x OHCI driver is polling for port status changes more frequently; OHCI is polling every 30 milliseconds: #define OHCI_RH_POLL_TIME 30000 http://src.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/common/sys/usb/hcd/openhci/ohci_hub.h#102 {e,o,u}hci_handle_root_hub_status_change should be visible in powertop... -- This message posted from opensolaris.org _______________________________________________ driver-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/driver-discuss
