From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754156AbaIAOZ4 (ORCPT ); Mon, 1 Sep 2014 10:25:56 -0400 Received: from mout.kundenserver.de ([212.227.126.187]:49890 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753398AbaIAOZm (ORCPT ); Mon, 1 Sep 2014 10:25:42 -0400 From: Arnd Bergmann To: linux-arm-kernel@lists.infradead.org Cc: Lee Jones , kgene.kim@samsung.com, linux@arm.linux.org.uk, naushad@samsung.com, Pankaj Dubey , Tomasz Figa , linux-kernel@vger.kernel.org, joshi@samsung.com, linux-samsung-soc@vger.kernel.org, broonie@kernel.org, thomas.ab@samsung.com, vikas.sajjan@samsung.com, chow.kim@samsung.com Subject: Re: [PATCH] mfd: syscon: Decouple syscon interface from syscon devices Date: Mon, 01 Sep 2014 16:24:27 +0200 Message-ID: <12348292.z1qJl96tVA@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20140901112549.GM7374@lee--X1> References: <1408694991-21615-1-git-send-email-pankaj.dubey@samsung.com> <4121644.3haxjiIdIo@wuerfel> <20140901112549.GM7374@lee--X1> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V02:K0:qERyDHGOp8/4GrWJDzhvLRl311yAKqtJ3Tk/E5r2Oyb xc/kwp3zGfYTU1YiunS3gjSs59gNFiB3IRPMdkfzfvX1qNr63d 2pgCVl0xRSXoDlZcZzZ8qa0OeAwtdSGHxbPYiIrovkNICjYC9D UpRabNUxmgJ21Ylded73fEdTJ4H/aE6a1n6ndQmjQxJuLhXoRD 75KRkWrXdDlRpukmeW+hqqn+UAz6mIoOiqahDgIM3mjkmjmaXq VTBSP2tlnvk/09zS0Gh4hKIM/tFnjLX6CtsyLQhCC0p41GKN7u WSHore0P8vF8FkCfWPfVS064hFzO6EVgY3zFRx/Sy0HNHErrgW euavMIbWEHhrnEmMg3bk= X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday 01 September 2014 12:25:49 Lee Jones wrote: > On Mon, 01 Sep 2014, Arnd Bergmann wrote: > > On Monday 01 September 2014 08:49:18 Lee Jones wrote: > > > On Fri, 22 Aug 2014, Pankaj Dubey wrote: > > > > > > > From: Tomasz Figa > > > > > > > > Currently a syscon entity can be only registered directly through a > > > > platform device that binds to a dedicated driver. However in certain use > > > > cases it is desirable to make a device used with another driver a syscon > > > > interface provider. For example, certain SoCs (e.g. Exynos) contain > > > > system controller blocks which perform various functions such as power > > > > domain control, CPU power management, low power mode control, but in > > > > addition contain certain IP integration glue, such as various signal > > > > masks, coprocessor power control, etc. In such case, there is a need to > > > > have a dedicated driver for such system controller but also share > > > > registers with other drivers. The latter is where the syscon interface > > > > is helpful. > > > > > > > > This patch decouples syscon object from syscon driver, so that it can be > > > > registered from any driver in addition to the original "syscon" platform > > > > driver. > > > > > > > > Signed-off-by: Tomasz Figa > > > > Signed-off-by: Pankaj Dubey > > > > --- > > > > > > > > RFC patch [1] was posted by Tomasz Figa. This patch addresses some of > > > > comments given by Arnd to RFC patch, and further decouples syscon from > > > > device model. It also gives flexibility of registering with syscon at > > > > early stage using device_node object. > > > > > > It would be helpful if Arnd gave this revision his blessing (Ack). > > > > I never saw a reason why we don't take this all the way as discussed > > a few times: Completely remove the dependency of syscon on having > > a platform driver for it, and make it possible to just call > > syscon_regmap_lookup_by_phandle() without having to register > > it first. > > I think this sounds like a good end-state. Migrating over by > supporting both methods in this way does sound like the correct thing > to do though. Doing so is likely to dramatically reduce the effect on > current users. Maybe I'm misreading the patch, but I don't see how it creates a migration path. What I want to end up with is infrastructure that lets anybody call syscon_regmap_lookup_by_pdevname or syscon_regmap_lookup_by_compatible (if they really need to) without needing the platform_driver for syscon. That should not require any form of compatibility layer because to the driver using it there is no API change. In contrast, this patch introduces a new of_syscon_{un,}register() interface that would get removed after the the above has been implemented, causing extra churn for any driver that also wants to provide a regmap-like interface. Arnd