From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751803AbdIEIyG (ORCPT ); Tue, 5 Sep 2017 04:54:06 -0400 Received: from lelnx194.ext.ti.com ([198.47.27.80]:20143 "EHLO lelnx194.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750913AbdIEIxp (ORCPT ); Tue, 5 Sep 2017 04:53:45 -0400 Subject: Re: [PATCH v3 3/5] dt-bindings: sdhci-omap: Add bindings for the sdhci-omap controller To: Tony Lindgren , Rob Herring References: <20170821142132.GH6008@atomide.com> <20170823054246.23927-1-kishon@ti.com> <0c7e0705-d9c2-4499-54ba-cbd84589dc01@ti.com> <20170829115050.3axlr5uysmqlhvd2@earth> <20170829135822.GR6008@atomide.com> <20170829170920.xpgk5ywlvfgrtbqi@rob-hp-laptop> <20170829173913.GD6008@atomide.com> CC: Sebastian Reichel , Ulf Hansson , Adrian Hunter , Sekhar Nori , Russell King , Ravikumar Kattekola , "linux-mmc@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" , linux-omap , "linux-arm-kernel@lists.infradead.org" From: Kishon Vijay Abraham I Message-ID: <06199a7e-456d-708d-6f2f-81f6bbfea2ba@ti.com> Date: Tue, 5 Sep 2017 14:22:55 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <20170829173913.GD6008@atomide.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Tuesday 29 August 2017 11:09 PM, Tony Lindgren wrote: > * Rob Herring [170829 10:09]: >> On Tue, Aug 29, 2017 at 06:58:23AM -0700, Tony Lindgren wrote: >>> * Sebastian Reichel [170829 04:51]: >>>> I would expect the conversion to look like the one done for UART, >>>> see CONFIG_SERIAL_OMAP vs CONFIG_SERIAL_8250_OMAP. Both use the >>>> same compatible value and you can choose using kernel configuration. >>> >>> That does not work unfortunately :( We are now stuck in a situation >>> where two drivers are attempting to probe with the same compatible >>> and we can't enable 8250_OMAP because of the user space breakage >>> with the device names. And I'm actuallly thinking we should add a >>> new compatible for 8250-omap to be able to start enabling it one >>> board at a time. >> >> Is that the only problem? Presumably, the SD driver doesn't have a >> userspace facing issue. > > No userspace issue with the sdhci-omap. But the sdhci-omap driver > still has the issue of trying enable it for everything at once and > expect everything to work. The sdhci-omap driver can already be > used for boards that don't need power management for example, but > will break things for devices running on batteries. > >>> It's best to enable devices to use the new compatible as things are >>> tested rather than hope for some magic "flag day" flip that might >>> never happen. Having two days attempting to probe with the same >>> binding just won't work. >> >> Aren't you just picking whether the flag day is in DT or the kernel? I >> guess you're assuming one kernel build and it would be switching all >> boards at one. > > Right, this would be risky and would take unnecessarily long > to use the new driver on boards that can already use it. While > power management won't work yet, I'd expect the sdhci-omap be > faster on SoCs that can do ADMA. > >>> So yeah, I agree with Kishon that we should stick with generic >>> and sdhci bindings. And then we can start already using it for >>> boards that can use it, then eventually when we're ready, start >>> parsing also the legacy bindings and maybe drop the old driver. >> >> I assume there are some other common properties you would switch to in >> the transition? You could make the legacy driver bail from probe based >> on presence or absence of other properties. Or you could just blacklist >> converted platforms in the legacy driver. The point is that the problems >> are solvable in the kernel. > > Yes this could be done too. But let's enable it on per-board > basis rather than attempt to flip it on at once. > >> But if your really want a new compatible, I don't really care. It's >> only one device. > > Both a new compatible or a check for some resource work just fine > for me as long as the driver can be selected on per-board basis. New compatible sounds simpler to me since it allows to select a driver per-MMC instance. (SDIO support is not added/validated in sdhci-omap). To summarize, we'll create new compatible and new bindings for sdhci-omap and start enabling sdhci-omap on per-board basis. When all the TI platforms starts to use sdhci-omap, omap-hsmmc will be removed at which point support for old compatible and old dt bindings will be added to sdhci-omap.c. Does this sound reasonable? Thanks Kishon