On Wed, Dec 7, 2011 at 1:30 PM, Pratyush Anand <pratyush.anand@xxxxxxxxx> wrote: > Hi, > > I am working with linux-2.6.38 and testing suspend to ram behaviour in > case usb2.0. > > 1. I have connected a HS device, so it is enumerated on EHCI. > 2. Now I do suspend to ram (echo mem > /sys/power/state). > 3. When I do resume, I see that the same HS device is now enumerated by OHCI. > 4. It happens because of following reasons: > a . Power of controller is lost during suspend. By reading > following link it seems that power should not be lost. > http://comments.gmane.org/gmane.linux.usb.general/29432 ;. But, we can > not prevent it , as USB controller and many other peripherals are in > same power island and , this island needs to be switched off in echo > mem operation. Lost vbus of USB bus will cause disconnect event for device, suspend/resume needs vbus is present, the remote wakeup will not be supported if vbus is not present. > b. Power on reset value of Configured flag (Bit 1 of EHCI offset > 0x50) is 0. So, default owner is companion controller. Therefore, OHCI > takes over and now device is enumerated by it. A new sdb node is > created with new bus and device number. However, successive suspend > and resume creates same node, as now device is always with OHCI. > > 5. Now question is, what should be workaround? I am doing following > workaround. Is this correct? or am I missing something and not able > to use already available feature of kernel? > > a. In my controller specific suspend, I keep track of > configured_flag. If it is set in controller, I set my software flag > too. > b. If configured_flag is set, then I also save ehci port status > of all the ports. > c. In resume, I check if configured flag was set. > d. If it was set, then I check if port was powered. > e. If it was powered, I set power bit (bit 12) and I check if a > device was present. > f. If a device was present, then I wait (with a timeout) till > device present bit (bit 0) becomes 1. > > g. With these modifications, I see that usb_port_resume function > is correctly able to see reset resume and device is enumerated with > same address and bus at EHCI. > > Please advice, if it is the right way. > > Regards > Pratyush > -- > 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 -- BR, Peter Chen -- 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
