From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: [PATCH v2 2/5] usb: musb: call musb_port_suspend from musb_bus_suspend Date: Wed, 02 Oct 2013 14:01:17 +0200 Message-ID: <524C0B0D.3020300@linutronix.de> References: <1380634797-29541-1-git-send-email-zonque@gmail.com> <1380634797-29541-3-git-send-email-zonque@gmail.com> <20131002104910.GD16680@linutronix.de> <524C001B.8040901@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <524C001B.8040901-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Daniel Mack Cc: linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, neumann-SRDuVqtxQLSzQB+pC5nmwQ@public.gmane.org, vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, balbi-l0cyMroinI0@public.gmane.org List-Id: linux-omap@vger.kernel.org On 10/02/2013 01:14 PM, Daniel Mack wrote: > On 02.10.2013 12:49, Sebastian Andrzej Siewior wrote: >> * Daniel Mack | 2013-10-01 15:39:54 [+0200]: >> >>> Make musb_port_suspend() externally available, and call it when to host >>> goes into suspend. This allows the core to go into suspend while a >>> device is connected. >> >> Sorry for asking this stupid question but what is usally happening when >> the host goes to suspend and a device is connected? I think it is >> disconnected & re-enumerated and resume and this not what you want, >> right? > > It is usually put into USB suspend and the host preserves its state. > After resume, the usb storage driver, for example, will not register new > partitions but expect things to be as they were before. That is, your > previously mounted devices remain functional. > > However, the enumeration process has to be done again, because when the > device looses power, it can't memorize its address. > >> What happens if the device is unplugged while the host is suspended and >> not there on resume? > > That condition is detected and a full teardown of the connected drivers > is conducted. Try what happens on your notebook when you do that. > Embedded systems should behave just the same. I had the feeling that the USB device gets disconnected and re-enumerated on resume. But if you say that the ehci-hcd saves the state and keeps the device connected if it wasn't disconnected during suspend then there is no reason for musb to behave differently. > Daniel Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html