From mboxrd@z Thu Jan 1 00:00:00 1970 From: Timur Subject: ehci-tegra issue with deep sleep Date: Tue, 11 Dec 2012 23:23:12 +0100 Message-ID: <50C7B250.7020409@riseup.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org Hi. I discovered a problem with USB host mode on a Nexus 7 running Android 4.2.x: USB slave devices will become undetectable ("not accepting address xx, error -71") after the host goes through a deep sleep cycle (60+ seconds loss of external power; running on battery). In this situation the methods tegra_ehci_suspend() and tegra_ehci_resume() are being called. I am _not_ experiencing this issue at all, when the host only goes through a light sleep cycle (less than 20 seconds of power loss). During light sleep, the methods tegra_ehci_suspend() and tegra_ehci_resume() are _not_ being called. The slave device (a USB DAC; many different products have been tested) is loosing power in both cases. But this does not seem to be the problem, because slave devices stays accessible, when the host (N7) only goes through light sleep. Is anyone aware of this problem? Has it been fixed since 3.1.10? Thank you. Timur Project on github: http://mehrvarz.github.com/usb-host-mode-power-management-nexus7 Discussion: "Can you charge & USB Host mode simultaneously?" http://rootzwiki.com/forum/512-nexus-7