From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Date: Fri, 12 May 2017 07:58:49 -0700 Message-ID: <20170512145849.GE3489@atomide.com> References: <20170511185528.GW3489@atomide.com> <20170511190100.GF7154@uda0271908> <20170511191005.GG7154@uda0271908> <20170511192013.GA4459@uda0271908> <20170511193810.GX3489@atomide.com> <20170511200220.GH7154@uda0271908> <20170511202306.GY3489@atomide.com> <20170511204406.GI7154@uda0271908> <20170511210628.GA3489@atomide.com> <20170512134042.GK7154@uda0271908> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170512134042.GK7154@uda0271908> Sender: linux-kernel-owner@vger.kernel.org To: Bin Liu , Moreno Bartalucci , Lars Melin , "linux-omap@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Alessio Igor Bogani List-Id: linux-omap@vger.kernel.org * Bin Liu [170512 06:43]: > On Thu, May 11, 2017 at 02:06:28PM -0700, Tony Lindgren wrote: > > > > Well maybe the minimal fix for now is just pretty much back to > > square one of this thread. This should keep VBUS always on. > > Then we can figure out some logic to cut VBUS later on. > > > > And yeah, the state machine is really hard to follow so some kind > > of clean up would be nice. > > Okay, figured out why clearing session in OTG_STATE_A_WAIT_BCON, it is > not for error condition handling (which is done in musb-core), but for > going back to b_idle state from a_host for dual-role mode. otg_timer() > (now is dsps_check_status()) was only called for otg port originally, so > it wasn't an issue, until started calling it for host mode as well when > runtime PM was added. OK makes sense. > > 8< ------------------- > > --- a/drivers/usb/musb/musb_dsps.c > > +++ b/drivers/usb/musb/musb_dsps.c > > @@ -245,7 +245,6 @@ static int dsps_check_status(struct musb *musb, void *unused) > > dsps_mod_timer_optional(glue); > > break; > > case OTG_STATE_A_WAIT_BCON: > > - musb_writeb(musb->mregs, MUSB_DEVCTL, 0); > > skip_session = 1; > > /* fall */ > > > > So the above patch breaks otg port when switching from host to device > mode. The following change should solve it. But Tony do you see any way > to improve it with glue->vbus_irq? OK. No better ideas except I think we should probably have a separate timer for keeping VBUS on after state changes eventually. I guess the real test here would be to connect a USB modem that changes state to the am335x-evm OTG port and make sure it works with commit similar to d680414d0f42 ("ARM: dts: Configure BeagleBone peripheral USB VBUS irq"). And also without configuring the vusb_irq. For the patch below, seems like the way to go for the fix assuming it fixes the $subject issue: Acked-by: Tony Lindgren > 8< -------------------- > diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c > index 9c7ee26ef388..465281244596 100644 > --- a/drivers/usb/musb/musb_dsps.c > +++ b/drivers/usb/musb/musb_dsps.c > @@ -245,9 +245,14 @@ static int dsps_check_status(struct musb *musb, void *unused) > dsps_mod_timer_optional(glue); > break; > case OTG_STATE_A_WAIT_BCON: > + /* keep VBUS on for host-only mode */ > + if (musb->port_mode == MUSB_PORT_MODE_HOST) { > + dsps_mod_timer_optional(glue); > + break; > + } > musb_writeb(musb->mregs, MUSB_DEVCTL, 0); > skip_session = 1; > - /* fall */ > + /* fall through */ > > case OTG_STATE_A_IDLE: > case OTG_STATE_B_IDLE: