Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755877AbcCaGfO (ORCPT ); Thu, 31 Mar 2016 02:35:14 -0400 Received: from mail-yw0-f177.google.com ([209.85.161.177]:32879 "EHLO mail-yw0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754827AbcCaGfJ (ORCPT ); Thu, 31 Mar 2016 02:35:09 -0400 MIME-Version: 1.0 In-Reply-To: <87y48zgogi.fsf@intel.com> References: <20160325070937.GA22398@peterchendt> <878u10jjie.fsf@intel.com> <87y48zgogi.fsf@intel.com> Date: Thu, 31 Mar 2016 14:35:08 +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: 3002 Lines: 76 On 31 March 2016 at 14:18, Felipe Balbi wrote: > > Hi, > > Baolin Wang writes: >> [ text/plain ] >> 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()'. > > yes. > >> 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. > > they shouldn't detect is get_type(), the semantics doesn't work. If, at > some point, we have to do SW detection of the charger, then a new > ->charger_detect() method will have to be added. Make sense. > > -- > balbi -- Baolin.wang Best Regards