Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751826AbdC0RRd (ORCPT ); Mon, 27 Mar 2017 13:17:33 -0400 Received: from lelnx193.ext.ti.com ([198.47.27.77]:38520 "EHLO lelnx193.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751344AbdC0RRU (ORCPT ); Mon, 27 Mar 2017 13:17:20 -0400 Date: Mon, 27 Mar 2017 12:15:34 -0500 From: Bin Liu To: Tony Lindgren CC: 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: <20170327171534.GA4403@uda0271908> Mail-Followup-To: Bin Liu , Tony Lindgren , Moreno Bartalucci , Lars Melin , "linux-omap@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Alessio Igor Bogani 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> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170327165946.GL10760@atomide.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1322 Lines: 26 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. 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. Regards, -Bin.