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. 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
