Messages in this thread | | | From | "Grover, Andrew" <> | Subject | [PATCH] USB suspend when no devices attached | Date | Fri, 16 Mar 2001 16:21:28 -0800 |
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Hi all.
This is a preliminary patch against 2.4.2 to uhci.c that puts the host controller into global suspend when there are no devices attached. This conserves power on mobile systems, and because suspending the host controller ceases UHCI's incessant busmastering activity, it allows the CPU to enter a deeper idle state.
The main problem with this implementation is that it just looks at the 2 root hub ports and suspends if nothing is connected. Ideally, it would be smart enough to realize it can also suspend when only hubs are present, or when all devices on the USB are also suspended. I hope a USB expert can add these enhancements, as it's beyond me.
You should be able to verify this patch is working in one of two ways: 1) Turn on USB debug messages, and look for suspend_hc and wakeup_hc messages 2) Download the latest ACPI patch from http://developer.intel.com/technology/iapc/acpi/downloads.htm and verify that /proc/acpi/processor/0/status shows mostly 0's for busmastering activity (as opposed to mostly F's) when no USB devices are connected.
Thanks -- Regards -- Andy
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