On Fri, 16 Dec 2005, Marco Calviani wrote: > Hi list, > i would like to pose a question regarding the USB drivers: i've > experienced that with USB modules loaded my CPU cannot go in C3 mode, > in this way spending more energy that is actually required by the > system because the modules are continously polling for signal.
That's true if you have a USB device attached to the computer. If no devices are attached then the driver modules do not prevent the CPU from going into C3. > I would definitely like my CPU to go in the C3 mode also using an USB > connected mouse. > Some ideas that i've been given from the acpi-devel list is to: > > 1) increase the USB polling time, so that the CPU is able to go in > sleep mode during these intervals I don't know if that is practical. How quickly can the CPU enter and leave C3? Typical polling times are on the order of a few tens of milliseconds, and the design of the drivers does not allow them to go much higher. Even worse, the real problem is the use of DMA. No matter how slow the polling is, the USB controller needs to use DMA at least once per millisecond. That alone is enough to prevent the CPU from going into C3. > 2) Fix USB to send mouse in runtime sleep state (thanks Pavel), in > order to give the possibility to the CPU to go C3 as long as i'm not > actively moving the mouse. That's the holy grail of USB runtime power management. People are working on it (slowly perhaps, but working). We'll get there eventually. > I'm not definitely an USB driver programmer.... > Could you please suggest me how to implement these settings? Start by becoming a USB driver programmer. :-) Alan Stern ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
