Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755980AbcCaGhf (ORCPT ); Thu, 31 Mar 2016 02:37:35 -0400 Received: from mail-yw0-f182.google.com ([209.85.161.182]:34444 "EHLO mail-yw0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755868AbcCaGhb (ORCPT ); Thu, 31 Mar 2016 02:37:31 -0400 MIME-Version: 1.0 In-Reply-To: References: <20160325070937.GA22398@peterchendt>

Date: Thu, 31 Mar 2016 14:37:30 +0800 Message-ID: Subject: Re: [PATCH v8 0/4] Introduce usb charger framework to deal with the usb gadget power negotation From: Baolin Wang To: Jun Li Cc: Peter Chen , Felipe Balbi , Greg KH , Sebastian Reichel , Dmitry Eremin-Solenikov , David Woodhouse , Peter Chen , Alan Stern , "r.baldyga@samsung.com" , Yoshihiro Shimoda , Lee Jones , Mark Brown , Charles Keepax , "patches@opensource.wolfsonmicro.com" , Linux PM list , USB , "device-mainlining@lists.linuxfoundation.org" , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3962 Lines: 88 On 31 March 2016 at 14:12, Jun Li wrote: > Hi > >> -----Original Message----- >> From: Baolin Wang [mailto:baolin.wang@linaro.org] >> Sent: Thursday, March 31, 2016 1:23 PM >> To: Jun Li >> Cc: Peter Chen ; Felipe Balbi ; >> Greg KH ; Sebastian Reichel ; >> Dmitry Eremin-Solenikov ; David Woodhouse >> ; Peter Chen ; Alan Stern >> ; r.baldyga@samsung.com; Yoshihiro Shimoda >> ; Lee Jones ; Mark >> Brown ; Charles Keepax >> ; patches@opensource.wolfsonmicro.com; >> Linux PM list ; USB ; >> device-mainlining@lists.linuxfoundation.org; LKML > kernel@vger.kernel.org> >> Subject: Re: [PATCH v8 0/4] Introduce usb charger framework to deal with >> the usb gadget power negotation >> >> On 30 March 2016 at 18:58, Jun Li wrote: >> >> >> >> > Seems you don't want to guarantee charger type detection is >> >> >> >> > done before gadget connection(pullup DP), right? >> >> >> >> > I see you call usb_charger_detect_type() in each gadget usb >> >> >> >> > state >> >> >> >> changes. >> >> >> >> >> >> >> >> I am not sure I get your point correctly, please correct me if >> >> >> >> I misunderstand you. >> >> >> >> We need to check the charger type at every event comes from the >> >> >> >> usb gadget state changes or the extcon device state changes, >> >> >> >> which means a new charger plugin or pullup. >> >> >> >> >> >> >> > >> >> >> > According to usb charger spec, my understanding is you can't do >> >> >> > real charger detection procedure *after* gadget >> >> >> > _connection_(pullup DP), also I don't >> >> >> >> >> >> Why can not? Charger detection is usually from PMIC. >> >> > >> >> > Charger detection process will impact DP/DM line state, see usb >> >> > charger spec v1.2 for detail detection process, section 4.6.3 says: >> >> > >> >> > "A PD is allowed to *disconnect* and repeat the charger detection >> >> > process multiple times while attached. The PD is required to wait >> >> > for a time of at least TCP_VDM_EN max between disconnecting and >> >> > restarting the charger detection process." >> >> > >> >> > As Peter mentioned, the charger detection should happen between >> >> > VBUS detection and gadget pull up DP for first plug in case. So >> >> > when&after gadget connect (pullup DP), you should already know the >> charger type. >> >> >> >> Make sense. In our company's solution, charger detection can be done >> >> by hardware from PMIC at first, then it will not affect the DP/DM >> >> line when gadget starts to enumeration. >> > >> > I see, charger type detection is done automatically by PMIC when VBUS >> > is detected in your case, you just assume the process is complete >> > before SW do gadget connect. To make the framework common, you may do >> one time charger type check when vbus is on, and save it to avoid repeat >> charger type check. >> >> OK. I'll add one judgement to check if the charger type is set in >> 'usb_charger_detect_type()' function. > > Just adding a judgement isn't enough here, your framework should make sure > usb_charger_detect_type() is called before gadget connect, with that, the > existing caller place just gets the charger type from the saved value. > The real charger type detection done by usb_charger_detect_type() can > be called only when vbus is on. > e.g. maybe in usb_udc_vbus_handler() before usb_udc_connect_control(). Yeah, Like Felipe suggested, I think we need to introduce one 'charger_detect()' method to do the SW charger type detection at the right gadget state. Thanks for your comments. >> >> -- >> Baolin.wang >> Best Regards -- Baolin.wang Best Regards