Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754003AbdC1O7p (ORCPT ); Tue, 28 Mar 2017 10:59:45 -0400 Received: from muru.com ([72.249.23.125]:42440 "EHLO muru.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752418AbdC1O7n (ORCPT ); Tue, 28 Mar 2017 10:59:43 -0400 Date: Tue, 28 Mar 2017 07:59:08 -0700 From: Tony Lindgren To: Moreno Bartalucci Cc: Bin Liu , 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: <20170328145908.GT10760@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> <11BBAEC7-0B26-40FE-963E-811F7853F2FE@tecnorama.it> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <11BBAEC7-0B26-40FE-963E-811F7853F2FE@tecnorama.it> 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: 1820 Lines: 38 * Moreno Bartalucci [170327 23:12]: > > Il giorno 27 mar 2017, alle ore 19:15, Bin Liu ha scritto: > > > > […] > > > > 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. > > > > 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. > > > > During my research, I used this patch to try to print the status of the usb port: > > --- a/drivers/usb/musb/musb_dsps.c 2017-03-13 09:34:31.000000000 +0100 > +++ b/drivers/usb/musb/musb_dsps.c 2017-03-13 09:36:02.000000000 +0100 > @@ -245,6 +245,8 @@ static void otg_timer(unsigned long _mus > dev_dbg(musb->controller, "Poll devctl %02x (%s)\n", devctl, > usb_otg_state_string(musb->xceiv->otg->state)); > > + dev_emerg(musb->controller, "musb->xceiv->otg->state=%s, musb->port_mode=%d\n", usb_otg_state_string(musb->xceiv->otg->state),(int)musb->port_mode); > + > spin_lock_irqsave(&musb->lock, flags); > switch (musb->xceiv->otg->state) { > case OTG_STATE_A_WAIT_BCON: > > Unless I did something wrong, maybe it’s worth to notice that before the patch that apparently introduced this bug (2f3fd2c5bde1f94513c3dc311ae64494085ec371) I got nothing printed anywhere. > With that patch applied, instead, I got the line printed in dmesg. > I might be wrong but my assumption is that without that patch otg_timer was never called. > If this is true, it would explain why writing 0 on DEVCTL didn’t bother anything: it never happened. OK yeah that makes sense. Thanks, Tony