From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932467AbcHXJDs (ORCPT ); Wed, 24 Aug 2016 05:03:48 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:33826 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750999AbcHXJDp (ORCPT ); Wed, 24 Aug 2016 05:03:45 -0400 Date: Wed, 24 Aug 2016 16:53:35 +0800 From: Peter Chen To: Vaibhav Hiremath , robh+dt@kernel.org Cc: Peter Chen , gregkh@linuxfoundation.org, stern@rowland.harvard.edu, ulf.hansson@linaro.org, broonie@kernel.org, sre@kernel.org, robh+dt@kernel.org, shawnguo@kernel.org, dbaryshkov@gmail.com, dwmw3@infradead.org, mark.rutland@arm.com, devicetree@vger.kernel.org, k.kozlowski@samsung.com, linux-usb@vger.kernel.org, oscar@naiandei.net, pawel.moll@arm.com, arnd@arndb.de, linux-pm@vger.kernel.org, festevam@gmail.com, s.hauer@pengutronix.de, stephen.boyd@linaro.org, linux-kernel@vger.kernel.org, troy.kisky@boundarydevices.com, stillcompiling@gmail.com, p.zabel@pengutronix.de, mail@maciej.szmigiero.name, mka@chromium.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v6 0/8] power: add power sequence library Message-ID: <20160824085335.GB27233@shlinux2> References: <1471252398-957-1-git-send-email-peter.chen@nxp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 23, 2016 at 04:02:48PM +0530, Vaibhav Hiremath wrote: > > > On Monday 15 August 2016 02:43 PM, Peter Chen wrote: > >Hi all, > > > >This is a follow-up for my last power sequence framework patch set [1]. > >According to Rob Herring and Ulf Hansson's comments[2], I use a generic > >power sequence library for parsing the power sequence elements on DT, > >and implement generic power sequence on library. The host driver > >can allocate power sequence instance, and calls pwrseq APIs accordingly. > > > >In future, if there are special power sequence requirements, the special > >power sequence library can be created. > > > >This patch set is tested on i.mx6 sabresx evk using a dts change, I use > >two hot-plug devices to simulate this use case, the related binding > >change is updated at patch [1/6], The udoo board changes were tested > >using my last power sequence patch set.[3] > > > >Except for hard-wired MMC and USB devices, I find the USB ULPI PHY also > >need to power on itself before it can be found by ULPI bus. > > > >[1] http://www.spinics.net/lists/linux-usb/msg142755.html > >[2] http://www.spinics.net/lists/linux-usb/msg143106.html > >[3] http://www.spinics.net/lists/linux-usb/msg142815.html > (Please ignore my response on V2) > > Sorry being so late in the discussion... > > If I am not missing anything, then I am afraid to say that the > generic library > implementation in this patch series is not going to solve many of > the custom > requirement of power on, off, etc... > I know you mentioned about adding another library when we come > across such platforms, but should we not keep provision (or easy > hooks/path) > to enable that ? > > Let me bring in the use case I am dealing with, > > > Host > | > V > USB port > ------------------------------------------------------------ > | > V > USB HUB device (May need custom on/off seq) > | > V > ============================= > | | > V V > Device-1 Device-2 > (Needs special power (Needs special power > on/off sequence. on/off sequence. > Also may need custom Also, may need custom > sequence for sequence for > suspend/resume) suspend/resume) > > > Note: Both Devices are connected to HUB via HSIC and may differ > in terms of functionality, features they support. > > In the above case, both Device-1 and Device-2, need separate > power on/off sequence. So generic library currently we have in this > patch series is not going to satisfy the need here. > > I looked at all 6 revisions of this patch-series, went through the > review comments, and looked at MMC power sequence code; > what I can say here is, we need something similar to > MMC power sequence here, where every device can have its own > power sequence (if needed). > > I know Rob is not in favor of creating platform device for > this, and I understand his comment. > If not platform device, but atleast we need mechanism to > connect each device back to its of_node and its respective > driver/library fns. For example, the Devices may support different > boot modes, and platform driver needs to make sure that > the right sequence is followed for booting. > > Peter, My apologies for taking you back again on this series. > I am OK, if you wish to address this in incremental addition, > but my point is, we know that the current generic way is not > enough for us, so I think we should try to fix it in initial phase only. > Rob, it seems generic power sequence can't cover all cases. Without information from DT, we can't know which power sequence for which device. -- Best Regards, Peter Chen