From mboxrd@z Thu Jan 1 00:00:00 1970 From: hdegoede@redhat.com (Hans de Goede) Date: Thu, 25 Aug 2016 19:59:46 +0200 Subject: [PATCH v2 7/7] musb: sunxi: Add support for platform_set_mode In-Reply-To: <20160822161037.GK1853@uda0271908> References: <1471288892-21702-1-git-send-email-hdegoede@redhat.com> <1471288892-21702-8-git-send-email-hdegoede@redhat.com> <20160819213049.GC1853@uda0271908> <2a55a1bf-7ebf-3ab4-b231-85eba20103f1@redhat.com> <20160822141158.GF1853@uda0271908> <9699b62e-421a-ae8e-c25e-ef48beb84ce0@redhat.com> <20160822152421.GH1853@uda0271908> <20160822153842.GI1853@uda0271908> <2e1d2bb6-c3c4-17ab-79a6-8f9efa45a831@redhat.com> <20160822161037.GK1853@uda0271908> Message-ID: <00986b3a-1a2a-1c67-f8bd-3a4c916cfbba@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On 22-08-16 18:10, Bin Liu wrote: > 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: >> >> >> >>>>>>>>> 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. Ah right, I ran some tests and indeed the hcd does not see a disconnect on role-change unless musb_root_disconnect() gets called, I'll send a v4 fixing this. Thank you for catching this. Regards, Hans > > 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