Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752026AbcCaFd1 (ORCPT ); Thu, 31 Mar 2016 01:33:27 -0400 Received: from mail-yw0-f171.google.com ([209.85.161.171]:36396 "EHLO mail-yw0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750975AbcCaFdZ (ORCPT ); Thu, 31 Mar 2016 01:33:25 -0400 MIME-Version: 1.0 In-Reply-To: <878u10jjie.fsf@intel.com> References: <20160325070937.GA22398@peterchendt> <878u10jjie.fsf@intel.com> Date: Thu, 31 Mar 2016 13:33:24 +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: Felipe Balbi Cc: Jun Li , Peter Chen , 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: 2533 Lines: 62 On 30 March 2016 at 19:24, Felipe Balbi 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 > > assuming this finishes before gadget starts is a bad idea. It would've > been much more robust to delay usb_gadget_connect() until we KNOW > charger detection has completed. It is hardware action to detect the charger type quickly. It actually *gets* the charger type and does not means *detect* charger type in 'usb_charger_detect_type()' function. Maybe I need to change the function name as 'usb_charger_get_type()'. If some udc drivers want to detect charger type in 'gadget->ops->get_charger_type()' callback, they should avoid impacting DP/DM line state at the right gadget state. Thanks. > > -- > balbi -- Baolin.wang Best Regards