From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752726AbbDCNiu (ORCPT ); Fri, 3 Apr 2015 09:38:50 -0400 Received: from devils.ext.ti.com ([198.47.26.153]:48964 "EHLO devils.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752465AbbDCNir (ORCPT ); Fri, 3 Apr 2015 09:38:47 -0400 Message-ID: <551E97CE.4000501@ti.com> Date: Fri, 3 Apr 2015 19:08:22 +0530 From: Kishon Vijay Abraham I User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: NeilBrown CC: NeilBrown , Tony Lindgren , , GTA04 owners , , Pavel Machek , , Subject: Re: [PATCH 0/5] Enhancements to twl4030 phy to support better charging - V2 References: <20150322223307.21765.62974.stgit@notabene.brown> <551325B0.1090308@ti.com> <20150326082219.510ac598@notabene.brown> <55134BEE.7050406@ti.com> <20150401154102.5f57ec1e@notabene.brown> In-Reply-To: <20150401154102.5f57ec1e@notabene.brown> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +Extcon MAINTAINERS Hi, On Wednesday 01 April 2015 10:11 AM, NeilBrown wrote: > On Thu, 26 Mar 2015 05:29:42 +0530 Kishon Vijay Abraham I > wrote: > >> Hi NeilBrown, >> >> On Thursday 26 March 2015 02:52 AM, NeilBrown wrote: >>> On Thu, 26 Mar 2015 02:46:32 +0530 Kishon Vijay Abraham I >>> wrote: >>> >>>> Hi, >>>> >>>> On Monday 23 March 2015 04:05 AM, NeilBrown wrote: >>>>> Hi Kishon, >>>>> I wonder if you could queue the following for the next merge window. >>>>> They allow the twl4030 phy to provide more information to the >>>>> twl4030 battery charger. >>>>> There are only minimal changes since the first version, particularly >>>>> documentation has been improved. >>>> >>>> There are quite a few things in this series which use the USB PHY library >>>> interface which is kindof deprecated. We should try and use the Generic PHY >>>> library for all of them. It would also be better to add features to the >>>> PHY framework if the we can't achieve something with the existing PHY >>>> framework. >>> >>> Hi, >>> are you able to more specific at all? What is the "USB PHY library"? >>> Where exactly is the "PHY framework"? >> >> There is a USB PHY library that exists in drivers/usb/phy/phy.c and there is >> a Generic PHY framework that is present in drivers/phy/phy-core.c. twl4030 >> actually supports both the framework. >> >> In your patch whatever uses struct usb_phy uses the old USB PHY library and >> whatever uses struct phy uses the generic PHY framework. (Actually your patch >> does not use the PHY framework at all). We want to deprecate using the USB PHY >> library and make everyone use the generic PHY framework. Adding features >> to a driver using the USB PHY library will make the transition to generic PHY >> framework a bit more difficult. >> >> Now all the features that is supported in the USB PHY library may not be >> supported by the PHY framework. So we should start extending the PHY framework >> instead of using the USB PHY library. >> >> One think I noticed in your driver is using atomic notifier chain. IMO extcon >> framework should be used in twl4030 USB driver to notify the controller driver >> instead of using USB PHY notifier. For all other things we have to see if it >> can be added in the PHY framework. > > I've had a look at the code with these issues in mind, and there is one issue > that I'm not sure about. > > In phy-twl4030-usb, the usb_phy is used to hold a reference to the > 'struct otg', and for passing cable state changes to the notifier. right now we directly call omap_musb_mailbox no? we don't use notifiers right? > > The former probably has to stay until musb can keep a reference to the otg, > separate form the usb_phy. The latter can be changed to use extcon - to > some extent. I actually have patches to do that from a couple of years back, > but I never proceeded with them. > > The problem is that one thing that needs to be communicated to the charger is > the max current that was negotiated by a "Standard Downstream Port". > This could be 500mA from a powered hum, or much less from an unpowered hub. > (Currently the usb gadget code does negotiated between different > possibilities, but it could and hopefully will one day). > > With the notifier chain there is an easy way to communicate the allowed > current once it is negotiated. e.g. ab8500_usb_set_power() does this. > > 'struct phy' has no equivalent of the 'set_power' callback which 'struct > usb_phy' provides, and extcon has no mechanism (that I can see) for > communicating a number - just binary cable states. Chanwoo Choi, Can this be modified so that we can communicate numbers like in the case of EXTCON_CHARGE_DOWNSTREAM? > > Presumably a 'set_power' method could be added to 'struct phy' so the > usb-core can communicate the number to the phy, but it is not clear to me how > the 'phy' can communicate it to the charger. Should the PHY be involved in all this? We can make the gadget driver directly communicate the value to the charger no? > The 'phy' could provide an API to request the current negotiated max current, > but there still needs to be a way to let the charger know that this has > changed. > That could in theory be done via extcon, by having a secondary > 'USB_connected' cable type, but it isn't really a cable type and pretending > that it is seems wrong. I think EXTCON_CHARGE_DOWNSTREAM was created for that purpose. Chanwoo? Thanks Kishon