From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: Changes to power management in ehci-tegra Date: Tue, 17 Apr 2012 17:28:12 -0600 Message-ID: <4F8DFC8C.5010001@wwwdotorg.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alan Stern Cc: Benoit Goby , linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, USB list List-Id: linux-tegra@vger.kernel.org On 04/17/2012 08:56 AM, Alan Stern wrote: > On Mon, 16 Apr 2012, Stephen Warren wrote: > >>>> The EHCI controller's active_kids count stays at 1 all the time. I >>>> assume that's the root USB hub device. Looking in its power/ directory, >>>> I see that even when nothing is plugged in, runtime_status==enabled, >>>> even with no active_kids or runtime_usage: >>> >>> That does indeed sound like a bug. Aha, there's a CONFIG_USB_SUSPEND which I didn't have enabled. Now I see the controller suspending. However, the controller suspends immediately the system boots even if there's a device already connected, and never resumes if there wasn't connected at boot, but one is plugged in later. In this state, I must set tegra-ehci.2/usb3/power/control=on to get anything to work. Forcing just the controller on (tegra-ehci.2/power/control=on) doesn't fix this. After than, I can set tegra-ehci.2/usb3/power/control=auto, and see the root hub (tegra-ehci.2/usb3/power) suspending/resuming as devices are unplugged/plugged. I just can't have tegra-ehci.2/power/control=auto while nothing is plugged in, or the cycle starts again. I assume this a bug in the Tegra EHCI driver's suspend implementation?