SPARC: USB Power Management

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

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. Devices that support remote wake up can notify the system to wake up everything in the device's path, so that the device can be used. 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 wake up capability. A USB printer is power-managed only between two print jobs.

When power management is running to reduce power consumption, USB leaf devices are powered down first. 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.