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 X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1939FC433DF for ; Thu, 2 Jul 2020 09:13:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1D5120702 for ; Thu, 2 Jul 2020 09:13:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=walle.cc header.i=@walle.cc header.b="Z5NTFwts" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727905AbgGBJM7 (ORCPT ); Thu, 2 Jul 2020 05:12:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726183AbgGBJM7 (ORCPT ); Thu, 2 Jul 2020 05:12:59 -0400 Received: from ssl.serverraum.org (ssl.serverraum.org [IPv6:2a01:4f8:151:8464::1:2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E8278C08C5C1; Thu, 2 Jul 2020 02:12:58 -0700 (PDT) Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id AC46622EEB; Thu, 2 Jul 2020 11:12:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1593681177; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sYkGBHvaNTyBI74MG9qO6W/wGpDKi9edSCvGAhgdkmw=; b=Z5NTFwtsFTYlze4XpyzMl067BvWkIbwhHTjSbiqKRE16dig9ea7I8Zhk/I9+hsAgGHhoHk 4pPkMKBrrjJp3+gbmZNXUe5DHCPV8JllhP1smmyGy3tt6bg4fn+kz2tky67/5dmfpzXYK1 eiaDSv/hOT3BDEbjpFFUsNa07btoD34= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 02 Jul 2020 11:12:56 +0200 From: Michael Walle To: Lee Jones Cc: Wolfram Sang , robh+dt@kernel.org, broonie@kernel.org, gregkh@linuxfoundation.org, andriy.shevchenko@linux.intel.com, devicetree@vger.kernel.org, linus.walleij@linaro.org, bgolaszewski@baylibre.com, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/1] mfd: Add I2C based System Configuaration (SYSCON) access In-Reply-To: <20200702081825.GR1179328@dell> References: <20200622075145.1464020-1-lee.jones@linaro.org> <20200701070434.GP1179328@dell> <5d1d41504172d86d395b0135923f6f02@walle.cc> <20200702065412.GO1179328@dell> <20200702081825.GR1179328@dell> User-Agent: Roundcube Webmail/1.4.6 Message-ID: <58ae64ebf22707ad1725987615b355c2@walle.cc> X-Sender: michael@walle.cc Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 2020-07-02 10:18, schrieb Lee Jones: > On Thu, 02 Jul 2020, Michael Walle wrote: > >> Am 2020-07-02 08:54, schrieb Lee Jones: >> > On Wed, 01 Jul 2020, Michael Walle wrote: >> > >> > > Am 2020-07-01 09:04, schrieb Lee Jones: >> > > > On Wed, 01 Jul 2020, Michael Walle wrote: >> > > > >> > > > > Hi Lee, >> > > > > >> > > > > Am 2020-06-30 11:16, schrieb Michael Walle: >> > > > > > I'm just trying to use this for my sl28 driver. Some remarks, see below. >> > > > > > >> > > > > > Am 2020-06-22 09:51, schrieb Lee Jones: >> > > > > > > The existing SYSCON implementation only supports MMIO (memory mapped) >> > > > > > > accesses, facilitated by Regmap. This extends support for registers >> > > > > > > held behind I2C busses. >> > > > > > > >> > > > > > > Signed-off-by: Lee Jones >> > > > > > > --- >> > > > > > > Changelog: >> > > > > > > >> > > > > > > v3 => v4 >> > > > > > > - Add ability to provide a non-default Regmap configuration >> > > > > > > >> > > > > > > v2 => v3 >> > > > > > > - Change 'is CONFIG' present check to include loadable modules >> > > > > > > - s/#ifdef CONFIG_MFD_SYSCON_I2C/#if >> > > > > > > IS_ENABLED(CONFIG_MFD_SYSCON_I2C)/ >> > > > > > > >> > > > > > > v1 => v2 >> > > > > > > - Remove legacy references to OF >> > > > > > > - Allow building as a module (fixes h8300 0-day issue) >> > > > > > > >> > > > > > > drivers/mfd/Kconfig | 7 +++ >> > > > > > > drivers/mfd/Makefile | 1 + >> > > > > > > drivers/mfd/syscon-i2c.c | 104 >> > > > > > > +++++++++++++++++++++++++++++++++ >> > > > > > > include/linux/mfd/syscon-i2c.h | 36 ++++++++++++ >> > > > > > > 4 files changed, 148 insertions(+) >> > > > > > > create mode 100644 drivers/mfd/syscon-i2c.c >> > > > > > > create mode 100644 include/linux/mfd/syscon-i2c.h >> > >> > [...] >> > >> > > > > > This way, (a) a driver doesn't have to use "#include " just >> > > > > > to call to_i2c_client() (or i2c_verify_client()) and (b) you won't do it >> > > > > > all over again in all sub drivers. >> > > > > > >> > > > > > So you could just do a >> > > > > > regmap = syscon_i2c_to_regmap(pdev->dev.parent); >> > > > > > >> > > > > > I've also noticed that the mmio syscon uses device_node as parameter. >> > > > > > What >> > > > > > was the reason to divert from that? Just curious. >> > > > > >> > > > > How is this supposed to be used? >> > > > > >> > > > > I had something like the following in mind: >> > > > > >> > > > > &i2c { >> > > > > cpld@4a { >> > > > > compatible = "simple-mfd"; >> > > > > reg = <0x4a>; >> > > > > >> > > > > gpio@4 { >> > > > > compatible = "vendor,gpio"; >> > > > > reg = <0x4>; >> > > > > }; >> > > > > }; >> > > > > }; >> > > > >> > > > Yes, that was the idea. >> > > > >> > > > > But I think the childen are not enumerated if its an I2C device. And >> > > > > the actual i2c driver is also missing. >> > > > >> > > > What do you mean? Can you elaborate? >> > > >> > > There is no i2c_driver instance who would create the regmap. >> > >> > The regmap is created by the first caller of: >> > >> > syscon_i2c_to_regmap{_config}() >> >> But which one is an i2c_driver? All the sub devices are platform >> drivers >> and there should be no need for them to know that they are behind an >> i2c driver (or spi driver or just mmio). All they have to know is how >> to access the registers. >> >> > > If I'm >> > > reading the I2C code correctly, it won't probe any i2c device of a >> > > bus if there is no i2c_driver with an associated .probe() or >> > > .probe_new(). >> > >> > Why wouldn't the children be registered using i2c_driver? >> >> Where is the code which enumerates the children? > > Yes, I see the problem now. So I2C devices depend on a device > registering with the i2c_driver framework, which then probes the > device accordingly. Thus a physical driver is required to convert I2C > devices to platform devices. So this stops being an MFD problem and > starts being a 'simple-i2c' issue. :) Yes, but this is still MFD specifc, because no other normal (in lack of a better word, think of one-function-devices) I2C device has sub-nodes. Thus my proposal for that simple-mfd-i2c driver. And keep in mind that this likely isn't specific to I2C but also to SPI (without having looked at it). So in theory that simple-mfd-i2c, could also register a spi_driver which then registers an SPI regmap and enumerates the children. So this is not only an I2C topic, but IMHO still MFD. -michael