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Mon, 5 Mar 2018 06:07:46 -0500 Received: from mga14.intel.com ([192.55.52.115]:57483 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752630AbeCELHq (ORCPT ); Mon, 5 Mar 2018 06:07:46 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.47,426,1515484800"; d="asc'?scan'208";a="205569076" From: Felipe Balbi To: Baolin Wang , Roger Quadros Cc: USB , LKML Subject: Re: [PATCH] usb: dwc3: Prevent indefinite sleep in _dwc3_set_mode during suspend/resume In-Reply-To: References: <1519730526-22274-1-git-send-email-rogerq@ti.com> <87sh9l5z4l.fsf@linux.intel.com> <94cd6377-1327-2309-8d69-6ab0de2bdfd4@ti.com> <87po4i3o1v.fsf@linux.intel.com> Date: Mon, 05 Mar 2018 13:06:49 +0200 Message-ID: <87k1uq3ho6.fsf@linux.intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" Sender: linux-usb-owner@vger.kernel.org X-Mailing-List: linux-usb@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable Hi, Baolin Wang writes: >>> Roger Quadros writes: >>>>> Roger Quadros writes: >>>>>> In the following test we get stuck by sleeping forever in _dwc3_set_= mode() >>>>>> after which dual-role switching doesn't work. >>>>>> >>>>>> On dra7-evm's dual-role port, >>>>>> - Load g_zero gadget driver and enumerate to host >>>>>> - suspend to mem >>>>>> - disconnect USB cable to host and connect otg cable with Pen drive = in it. >>>>>> - resume system >>>>>> - we sleep indefinitely in _dwc3_set_mode due to. >>>>>> dwc3_gadget_exit()->usb_del_gadget_udc()->udc_stop()-> >>>>>> dwc3_gadget_stop()->wait_event_lock_irq() >>>>>> >>>>>> Let's clear the DWC3_EP_END_TRANSFER_PENDING flag on all endpoints >>>>>> so we don't wait in dwc3_gadget_stop(). >>>>>> >>>>>> Signed-off-by: Roger Quadros >>>>>> --- >>>>>> drivers/usb/dwc3/gadget.c | 14 ++++++++++++++ >>>>>> 1 file changed, 14 insertions(+) >>>>>> >>>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c >>>>>> index 2bda4eb..0a360da 100644 >>>>>> --- a/drivers/usb/dwc3/gadget.c >>>>>> +++ b/drivers/usb/dwc3/gadget.c >>>>>> @@ -3273,6 +3273,20 @@ int dwc3_gadget_init(struct dwc3 *dwc) >>>>>> >>>>>> void dwc3_gadget_exit(struct dwc3 *dwc) >>>>>> { >>>>>> + int epnum; >>>>>> + unsigned long flags; >>>>>> + >>>>>> + spin_lock_irqsave(&dwc->lock, flags); >>>>>> + for (epnum =3D 2; epnum < DWC3_ENDPOINTS_NUM; epnum++) { >>>>>> + struct dwc3_ep *dep =3D dwc->eps[epnum]; >>>>>> + >>>>>> + if (!dep) >>>>>> + continue; >>>>>> + >>>>>> + dep->flags &=3D ~DWC3_EP_END_TRANSFER_PENDING; >>>>>> + } >>>>>> + spin_unlock_irqrestore(&dwc->lock, flags); >>>>>> + >>>>>> usb_del_gadget_udc(&dwc->gadget); >>>>>> dwc3_gadget_free_endpoints(dwc); >>>>> >>>>> free endpoints is a better place for this. It's already going to free >>>>> the memory anyway. Might as well clear all flags to 0 there. >>>>> >>>> >>>> But it won't solve the deadlock issue. Since dwc3_gadget_free_endpoint= s() >>>> is called after usb_del_gadget_udc() and the deadlock happens when >>>> >>>> usb_del_gadget_udc()->udc_stop()->dwc3_gadget_stop()->wait_event_lock_= irq() >>>> >>>> and DWC3_EP_END_TRANSFER_PENDING flag is set. >>> >>> indeed. Iterating twice over the entire endpoint list seems >>> wasteful. Perhaps we just shouldn't wait when removing the UDC since >>> that's essentially what this patch will do, right? If you clear the flag >>> before calling ->udc_stop(), this means the loop in dwc3_gadget_stop() >>> will do nothing. Might as well remove it. >>> >> >> This means that we will never wait for DWC3_EP_END_TRANSFER_PENDING to c= lear >> in dwc3_gadget_stop() like we used to. This is perfectly fine, right? >> >> It makes sense to me as dwc3_gadget_stop() calls __dwc3_gadget_stop() wh= ich >> masks all interrupts and nobody will ever clear that flag if it was set. > > I don't think so. It can not mask the endpoint events, please check > the events which will be masked in DEVTEN register. The reason why we > should wait for DWC3_EP_END_TRANSFER_PENDING to clear is that, > sometimes the DWC3_DEPEVT_EPCMDCMPLT event will be triggered later > than 100us, but now we may have freed the gadget irq which will cause > crash. We could mask command complete events as soon as ->udc_stop() is called, right? Hmm, actually, __dwc3_gadget_stop() already clears DEVTEN completely. /me goes check databook At least on revision 2.60a of the databook, bit 10 is reserved. I wonder if that's the start of all the problems. 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