Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751891AbdC0R4t (ORCPT ); Mon, 27 Mar 2017 13:56:49 -0400 Received: from muru.com ([72.249.23.125]:42312 "EHLO muru.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353AbdC0R4m (ORCPT ); Mon, 27 Mar 2017 13:56:42 -0400 Date: Mon, 27 Mar 2017 10:55:37 -0700 From: Tony Lindgren 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 Subject: Re: [PATCH] usb-musb: keep VBUS on when device is disconnected 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-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170327171534.GA4403@uda0271908> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2002 Lines: 41 * 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