Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754273AbdC1GKZ convert rfc822-to-8bit (ORCPT ); Tue, 28 Mar 2017 02:10:25 -0400 Received: from out.consiagnet.it ([83.149.128.196]:47479 "EHLO out.consiagnet.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752760AbdC1GKX (ORCPT ); Tue, 28 Mar 2017 02:10:23 -0400 X-Spam-Flag: NO X-Spam-Score: -2.901 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 10.2 \(3259\)) Subject: Re: [PATCH] usb-musb: keep VBUS on when device is disconnected From: Moreno Bartalucci In-Reply-To: <20170327171534.GA4403@uda0271908> Date: Tue, 28 Mar 2017 08:10:00 +0200 Cc: Tony Lindgren , Lars Melin , "linux-omap@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Alessio Igor Bogani Content-Transfer-Encoding: 8BIT Message-Id: <11BBAEC7-0B26-40FE-963E-811F7853F2FE@tecnorama.it> 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> To: Bin Liu X-Mailer: Apple Mail (2.3259) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1665 Lines: 35 > 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. Regards, Moreno