On Fri, 17 Jun 2011, Amit Nagal wrote: > On Fri, Jun 17, 2011 at 2:44 PM, suman <vijayendra.suman@xxxxxxxxx> wrote: > > Hi Amit, > > > > How is the USB connected in your system Is it through some USB > > controller, or directly to some CPU GPIO pins, you can program CPU > > registers to power down but you need to check the CPU spec, this in > > effect will bring the power down. If it is connected through some USB > > controller you can check the Spec, they have such commands to power > > down the controller. > > > currently i am referring to EHCI specs rev 1.0 Section 4.2.4 "Port > Power " and Table 4-3 , it says : > > "The Port Power Control (PPC) bit in the HCSPARAMS register indicates > whether the USB 2.0 host > controller has port power control (See Section 2.2.3). When this bit > is a zero, then the host controller does > not support software control of port power switches. When in this > configuration, the port power is always > available and the companion host controllers must implement > functionality consistent with port power > always on. > When the PPC bit is a one, then the host controller implementation > includes port power switches. Each > available switch has an output enable, which is referred to in this > discussion as PortPowerOutputEnable (PPE). > PPE is controlled based on the state of the combination bits PPC bit, > EHCI Configured (CF)-bit and > individual Port Power (PP) bits . Table 4�3 illustrates the summary > behavioral model. " > > can this be used to achieve poweroff / on usb port ? It can _if_ the PPC bit is set to 1. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
