SPARC: USB Power Management

Suspending and resuming USB devices are fully supported on SPARC systems. However, do not suspend a devices that is busy and never remove a device when the system is powered off.

If the SPARC based system has power management enabled, the USB framework makes a best effort to power-manage all devices. Power-managing a USB device means that the hub driver suspends the port to which the device is connected. The device might or might not support remote wakeup. If the device supports remote wakeup, it wakes up the hub it is connected to, depending on the event, such as moving the mouse. The host system could also wake up the device if an application sends an I/O to the device.

All HID (keyboard, mouse, speakers, microphones), hub, and storage devices are power-managed by default if they support remote wakeup capability. A USB printer is power-managed only between two print jobs.

When you power-manage to reduce power consumption, USB leaf devices are powered down first. Then, after some delay, the parent hub is powered down. When all devices that are connected to this hub's ports are powered down, the hub is powered down after some delay. To achieve the most efficient power management, do not cascade many hubs.