On Mon, Aug 22, 2016 at 05:55:50PM +0200, Hans de Goede wrote: > Hi, > > On 22-08-16 17:38, Bin Liu wrote: > >On Mon, Aug 22, 2016 at 05:32:57PM +0200, Hans de Goede wrote: > > <snip> > > >>>>>>>When switching from host to peripheral mode, if an usb device is still > >>>>>>>plugged and enumerated, how do you handle the device disconnect? > >>>>>> > >>>>>>The phy code will report vbus low for long enough for the musb to end > >>>>>>the current session. It already does this for boards which do not > >>>>>>have working vbus detection. > >>>>> > >>>>>But you didn't disconnect DP/DM, right? then musb detects vbus is gone > >>>>>without receiving disconnect event, this is vbus error case, not a normal > >>>>>teardown. > >>>> > >>>>Correct, there is no way to disconnect DP/DM and reporting Vbus low for > >>>>a while does the trick. > >>> > >>>Without physically disconnecting DP/DM, we still have a way to properly > >>>teardown the enumerated devices. Please check musb_softconnect_write() > >>>in musb_debugfs.c. > >> > >>That is manipulating the session bit in the devctl reg, that does not > >>work to switch from device to host role or from host to device role, > >>at least not on allwinner's musb implementation. I've already tried that > >>before writing the code to report VBus low. > > > >I would think you have to call musb_root_disconnect() first to notify > >the core to teardown the enumerated devices. > > I tried that it does not help. It only affects the software state, the > hardware will still stay in host-mode if it does not see vbus low for > long enough). I didn't mean to use musb_root_disconnect() to replace your implementation. I suggest to add this call before lowing vbus to let the core tearing down the numerated devices. > > Note this is on devices which lack vbus detection (again this is simply > physically not available on the PCB, just like some PCB's miss the > id-pin). Normally this never is an issue, because when a host cable gets > unplugged from a AB connector we see the id pin go high, disable the > boards driving of Vbus and then the phy's Vbus detect will report low to > the musb controller. In this case, DP/DM get disconnected before vbus line, so musb_root_disconnect() gets called in handling the disconnect interrupt event. I think it is better simulate this in your usecase, which does not generate disconnect event. Regards, -Bin. > > Anyways this is a solved problem, the reporting of Vbus low has been > working fine for both boards which lack vbus-detection as well as > for role-changing from sysfs. > > Regards, > > Hans -- 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
