From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933625AbcKNMg4 (ORCPT ); Mon, 14 Nov 2016 07:36:56 -0500 Received: from mail-yb0-f180.google.com ([209.85.213.180]:36006 "EHLO mail-yb0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752944AbcKNMgx (ORCPT ); Mon, 14 Nov 2016 07:36:53 -0500 MIME-Version: 1.0 In-Reply-To: <87eg2ek7ye.fsf@notabene.neil.brown.name> References: <87k2cttptn.fsf@notabene.neil.brown.name> <87a8dls7yn.fsf@notabene.neil.brown.name> <871sytqrqh.fsf@notabene.neil.brown.name> <87a8dbni27.fsf@notabene.neil.brown.name> <87eg2ek7ye.fsf@notabene.neil.brown.name> From: Baolin Wang Date: Mon, 14 Nov 2016 20:36:51 +0800 Message-ID: Subject: Re: [PATCH v18 0/4] Introduce usb charger framework to deal with the usb gadget power negotation To: NeilBrown Cc: Felipe Balbi , Greg KH , Sebastian Reichel , Dmitry Eremin-Solenikov , David Woodhouse , robh@kernel.org, Jun Li , Marek Szyprowski , Ruslan Bilovol , Peter Chen , Alan Stern , grygorii.strashko@ti.com, Yoshihiro Shimoda , Lee Jones , Mark Brown , John Stultz , 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 On 14 November 2016 at 12:21, NeilBrown wrote: > On Thu, Nov 10 2016, Baolin Wang wrote: > >> Hi >> >> On 8 November 2016 at 04:36, NeilBrown wrote: >>> On Mon, Nov 07 2016, Baolin Wang wrote: >>> >>>> On 3 November 2016 at 09:25, NeilBrown wrote: >>>>> On Tue, Nov 01 2016, Baolin Wang wrote: >>>> >>>> I agree with your most opinions, but these are optimization. >>> >>> I see them as bug fixes, not optimizations. >>> >>>> Firstly I >>>> think we should upstream the USB charger driver. >>> >>> I think you missed the point. The point is that we don't *need* your >>> "USB charger driver" because all the infrastructure we need is *already* >>> present in the kernel. It is buggy and not used uniformly, and could >>> usefully be polished and improved. But the structure is already >>> present. >>> >>> If everyone just added new infrastructure when they didn't like, or >>> didn't understand, what was already present, the kernel would become >>> like the Mad Hatter's tea party, full of dirty dishes. >>> >>>> What I want to ask is >>>> how can we notify power driver if we don't set the >>>> usb_register_notifier(), then I think you give the answer is: power >>>> driver can register by 'struct usb_phy->notifier'. But why usb phy >>>> should notify the power driver how much current should be drawn, and I >>>> still think we should notify the current in usb charger driver which >>>> is better, and do not need to notify current for power driver in usb >>>> phy driver. >>> >>> I accept that it isn't clear that the phy *should* be involved in >>> communicating the negotiated power availability, but nor is it clear >>> that it shouldn't. The power does travel through the physical >>> interface, so physically it plays a role. >>> >>> But more importantly, it already *does* get told (in some cases). >>> There is an interface "usb_phy_set_power()" which exists explicitly to >>> tell the phy what power has been negotiated. Given that infrastructure >>> exists and works, it make sense to use it. >>> >>> If you think it is a broken design and should be removed, then fine: >>> make a case for that. Examine the history. Make sure you know why it >>> is there (or make sure that information cannot be found), and then >>> present a case as to why it should be removed and replaced with >>> something else. But don't just leave it there and pretend it doesn't >>> exist and create something similar-but-different and hope people will >>> know why yours is better. That way lies madness. >> >> Like Peter said, it is not only PHY can detect the USB charger type, >> which means there are other places can detect the charger type. > > If I understand Peter's example correctly, it shows a configuration > where the USB PHysical interface is partly implemented in the SOC and > partly in the PMIC. I appreciate that would make it more challenging to > implement a PHY driver, but there is no reason it should impact anything > outside of the PHY. Like Peter's example, it need to use controller register to pull up dp to begin the secondary detection, which is not belonged to phy driver and I don't think it is suitable we implemented these in phy driver. > >> Second, some controller need to detect the charger type manually which >> USB phy did not support. > > "manually" is an odd term to use in this context. Sorry for the confusing. > I think you mean that to detect the charger type you need to issue some > command to the hardware and wait for it to respond, then assess the > response. Yes. > That isn't at all surprising. The charger type is detected by measuring > resistance between ID and GND, which may require setting up a potential > and activating ADCs to measure the voltage. This can all be done > internally to the phy driver. > Sometimes it is easy (I did https://lkml.org/lkml/2015/2/23/746 for > twl4030, though it never got upstream). > The code for the imx7d does look more complex, but not intrinsically > different. But you should implement these in every phy driver, why not one standard framework? > >> Third, it did not handle what current should >> be drawn in USB phy. > > The standards define that. The extcon just reports the cable type. > Certainly it would be sensible to provide a library function to > translate from cable type to current range. You don't need a new > subsystem to do that, just a library function. I don't think the extcon should handle current things. For example, the extcon can not know the gadget speed, which is used to change the default current values for super speed gadget. > >> Fourth, we need integrate all charger plugin/out >> event in one framework, not from extcon, maybe type-c in future. > > Why not extcon? Given that a charger is connected by an external > connector, extcon seems like exactly the right thing to use. My mistake, what I mean is not only from extcon, maybe from other places in future. > > Obviously extcon doesn't report the current that was negotiated, but > that is best kept separate. The battery charger can be advised of the > available current either via extcon or separately via the usb > subsystem. Don't conflate the two. > > >> In a >> word, we need one standard integration of this feature we need, though >> like you said we should do some clean up or fix to make it better. > > But really, I'm not the person you need to convince. I'm just a vaguely > interested bystander who is rapidly losing interest. You need to > convince a maintainer, but they have so far shown remarkably little > interest. I don't know why, but I'd guess that reviewing a complex new > subsystem isn't much fun. Reviewing and applying clear bugfixes and > incremental improvements is much easier and more enjoyable. But that is > just a guess. Maybe you missed previous comments, and we had a lot of discussion about this patchset. Also Felipe had reviewed this patchset with some suggestion. -- Baolin.wang Best Regards