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: Mon, 27 Mar 2017 10:55:37 -0700 Message-ID: <20170327175536.GP10760@atomide.com> References: <20170315140801.97230-1-moreno.bartalucci@tecnorama.it> <20170324185836.GC19814@uda0271908> <2d10809f-d482-ffa9-30b7-8785e94ab102@gmail.com> <00882633-3F61-4010-A4D2-D04473282B10@tecnorama.it> <20170327131701.GA12674@uda0271908> <20170327143049.GG10760@atomide.com> <63FD9E13-2B70-485C-80A7-206BEC16905A@tecnorama.it> <20170327165946.GL10760@atomide.com> <20170327171534.GA4403@uda0271908> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20170327171534.GA4403@uda0271908> Sender: linux-usb-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bin Liu , Moreno Bartalucci , Lars Melin , "linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Alessio Igor Bogani List-Id: linux-omap@vger.kernel.org * Bin Liu [170327 10:17]: > On Mon, Mar 27, 2017 at 09:59:47AM -0700, Tony Lindgren wrote: > > * Moreno Bartalucci [170327 09:23]: > > > If I understood your patch, however, if the device (anyone, not just my one) takes longer to switch, VBUS is deasserted anyway. > > > > Yeah some of them can take at least 10 seconds even to enumerate. > > So probably we need to have to have some longer timeout set for > > OTG_STATE_A_WAIT_BCON, like 20 or 30 seconds. > > > > > Although this patch is working for me, personally I would prefer a solution which would not deassert VBUS. At least on a host only port. Honestly I don’t know how a dual role port should work. > > > > It's been really long time since I read the OTG spec. There > > may be some diagram showing the required timeouts in the spec > > if there is one for VBUS. > > > > Maybe we need some property to specify vbus-always-on-in-host-mode? > > The MUSB otg state machine has been changed in many place since the last > time I looked at it, and I am not sure how exactly it works now. Yup.. I looked up the timers in the OTG spec and they are described in chapter "8.5.5.2" as a_wait_bcon_tmo or a_wait_bcon_tmr. But I could not find any values for them. Anyways, clearly we want things working with real devices :) > If the $subject patch can correctly keep the VBUS on for host-only mode, > we can somehow use dr_modei value to distinguish the mode. We don't have > to create a new vbus-always-on-in-host-mode flag. VBUS has to be always > on in host-only mode anyway, until some error condition happens. Yeh and it seems PM still works with the $subject patch also for host mode. So maybe that's enough to fix the issue. Also I don't have any idea why for ages we have been writing 0 to devctl there.. Maybe we've had a bug there that only now shows up when we idle things. Anyways, for the $subject patch related to MUSB runtime PM: Tested-by: Tony Lindgren -- 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