From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D441EC433FE for ; Wed, 16 Nov 2022 14:02:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233733AbiKPOCZ (ORCPT ); Wed, 16 Nov 2022 09:02:25 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38120 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233143AbiKPOAS (ORCPT ); Wed, 16 Nov 2022 09:00:18 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ECB70209AE for ; Wed, 16 Nov 2022 05:57:10 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8944E61E1C for ; Wed, 16 Nov 2022 13:57:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D0582C433C1; Wed, 16 Nov 2022 13:57:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1668607029; bh=icU4I7RIgRLNY1cWYT1aruWSL+8MqM+CeYHqkxj7G4M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=mfcdaHIoG5bad1XTgqtegKoMoni3gJ7rGv0tAdPMtGnmpeFXcdmD95qMfH0WVHlIv 2dL/Yn+4DdsISc9XdDN8loUYubDD4IYeHGwvB/gOoGgEW+8FYaOwAf4m8kFFsrNWoq lib7U6lPDPNE+YkVP2EJJs7dpT++WsUSD9WXJsfU//6Eijw5SIoKjrXtPxI+BOnwAh +u2UP1CrpYQsM+iNXtOgvfO9Y4NCP06dR20DqflU49xk0LpmqOSX2RD4LCkILfTonu Ju7zqNJbta95pi4ejC+XhnmPESECVhFZ7VKy93eD+Vd1dWvQRQ5X7lHqydydBCMNPu tj2RHppy2+jHA== Date: Wed, 16 Nov 2022 13:57:04 +0000 From: Lee Jones To: Liu Ying Cc: Rob Herring , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, shawnguo@kernel.org, s.hauer@pengutronix.de, kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com Subject: Re: [PATCH RESEND] mfd: Add Freescale i.MX8qxp Control and Status Registers (CSR) module driver Message-ID: References: <20221017075702.4182846-1-victor.liu@nxp.com> <4dfb7699c33974a682d798071c85b431b87e5432.camel@nxp.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 16 Nov 2022, Liu Ying wrote: > On Tue, 2022-11-15 at 07:33 -0600, Rob Herring wrote: > > On Mon, Nov 14, 2022 at 11:22 PM Liu Ying wrote: > > > On Mon, 2022-11-14 at 14:54 -0600, Rob Herring wrote: > > > > On Mon, Nov 7, 2022 at 9:58 PM Liu Ying wrote: > > > > > Hi Lee, > > > > > > > > > > On Mon, 2022-11-07 at 09:05 +0000, Lee Jones wrote: > > > > > > On Wed, 02 Nov 2022, Liu Ying wrote: > > > > > > > > > > > > > Hi Lee, > > > > > > > > > > > > > > On Tue, 2022-11-01 at 13:53 +0800, Liu Ying wrote: > > > > > > > > Hi Lee, > > > > > > > > > > > > > > > > On Mon, 2022-10-31 at 15:40 +0000, Lee Jones wrote: > > > > > > > > > On Mon, 17 Oct 2022, Liu Ying wrote: > > > > > > > > > > > > > [...] > > > > > > > > > > > > + ret = devm_of_platform_populate(&pdev->dev); > > > > > > > > > > > > > > > > > > The use of this API does not constitute a MFD. > > > > > > > > > > > > > > > > > > Please use "simple-mfd" instead. > > > > > > > > > > > > > > > > simple-mfd devices have "ONLY_BUS" set in simple-pm-bus.c, so the > > > > > > > > simple-pm-bus driver would not populate child devices of simple-mfd > > > > > > > > devices. > > > > > > > > > > > > Right, simple-pm-bus will not populate child devices, because: > > > > > > > > > > simple-pm-bus.c may populate child devices of simple-pm-bus devices > > > > > because "ONLY_BUS" is _not_ set for simple-pm-bus devices. > > > > > > > > > > simple-pm-bus.c would _not_ populate child devices of simple-mfd > > > > > devices because "ONLY_BUS" is set for simple-mfd devices. > > > > > > > > > > > /* > > > > > > * These are transparent bus devices (not simple-pm-bus matches) that > > > > > > * have their child nodes populated automatically. So, don't need to > > > > > > * do anything more. We only match with the device if this driver is > > > > > > * the most specific match because we don't want to incorrectly bind to > > > > > > * a device that has a more specific driver. > > > > > > */ > > > > > > > > > > > > So "simple-mfd" must be populated elsewhere i.e. drivers/of/platform.c. > > > > > > > > > > If simple-mfd device is a child device of one device listed in > > > > > of_default_bus_match_table[], then it may be populated by > > > > > drivers/of/platform.c. But, in my case, simple-mfd device is a child > > > > > device of simple-pm-bus device(not listed in that table), so it will > > > > > not be populated by drivers/of/platform.c. Instead, > > > > > drivers/bus/simple-pm-bus.c would populate the simple-mfd device. > > > > > > > > > > > > > Also, the simple-pm-bus driver would not enable runtime > > > > > > > > power management for simple-mfd devices due to "ONLY_BUS", which > > > > > > > > means it would not propagate power management operations from child > > > > > > > > devices of simple-mfd devices to parent devices of simple-mfd > > > > > > > > devices. That's why a dedicated fsl-imx8qxp-csr driver is needed. > > > > > > > > > > > > This is more of an issue. > > > > > > > > > > > > Why can't this device use "simple-pm-bus" to have support for both > > > > > > auto-registration AND Runtime PM? > > > > > > > > > > If I change the compatible string of the CSR module from > > > > > "fsl,imx8qxp-mipi-lvds-csr", "syscon", "simple-mfd" > > > > > to > > > > > "fsl,imx8qxp-mipi-lvds-csr", "syscon", "simple-pm-bus", > > > > > all devices I'm interested in are populated and all relevant drivers > > > > > can probe. But, this change makes 'make dt_binding_check' for the > > > > > existing fsl,imx8qxp-csr.yaml fail: > > > > > > > > As 'simple-bus' is for MMIO devices, so is 'simple-pm-bus' with the > > > > addition of PM capabilities. That means you have registers defined > > > > (reg), but you don't. > > > > > > > > Either you have a block with mixed functions or you have separate > > > > blocks. If the register space is all mixed together, then it is the > > > > former and an MFD. Don't be designing your binding based on Linux > > > > behavior. > > > > > > Thanks for clarifying how to differetiate MFD and 'simple-bus'/'simple- > > > pm-bus'. I would say the register space of the CSR module is mixed > > > together, e.g., LVDS PHY child device has a register offset 0x00, > > > PXL2DPI child device has a register offset 0x40 and LDB child device > > > has register offsets 0x20 and 0xe0 in i.MX8qxp MIPI DSI/LVDS combo > > > subsystem CSR module register space. So, it appears to be a MFD. > > > > > > Lee, what do you think? If it is indeed an MFD, a new MFD driver for > > > the CSR module is needed then. > > > > There already exists a driver which does what you need, so why create > > a 2nd one? Just add the "fsl,imx8qxp-mipi-lvds-csr" compatible to the > > simple-pm-bus match table and don't set ONLY_BUS. Isn't that enough? > > Adding "fsl,imx8qxp-mipi-lvds-csr" and "fsl,imx8qm-lvds-csr" compatible > strings to the simple-pm-bus match table does work, but it tends to > make people think the CSR module is a bus instead of a MFD. MFDs don't exist. They're a figment of our imagination. If you want PM enabled and wish for your child devices to be auto-magically registered for you, simple-pm-bus is what you need. > It's kinka > straightforward if a MFD device driver lives in drivers/mfd directory. > However, since "simple-mfd" compatible is also in that match table, I > would add the CSR module's compatible strings to that match table if no > objections. Fine by me if it saves authoring a pointless driver. -- Lee Jones [李琼斯]