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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 114F3C83001 for ; Tue, 28 Apr 2020 14:29:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F17862072A for ; Tue, 28 Apr 2020 14:29:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727804AbgD1O3n (ORCPT ); Tue, 28 Apr 2020 10:29:43 -0400 Received: from mga06.intel.com ([134.134.136.31]:4285 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727108AbgD1O3n (ORCPT ); Tue, 28 Apr 2020 10:29:43 -0400 IronPort-SDR: kOZrIelPDgOUC3aJDJW9H80ah7VC/S2GDIWbHQz354UeEUlk3/wUSs6TRvijBEJrgEMrqAkN+V kbTVQZESG98A== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Apr 2020 07:29:42 -0700 IronPort-SDR: vGnHmY/BqlTIl3FGa5R64rDdkwKbnMHUnpT0wYGLkHb05hlF7l+pQ52NbGLIPzbFCXoyvBDAUH qkiQUfkvunvw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,328,1583222400"; d="scan'208";a="432201423" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga005.jf.intel.com with ESMTP; 28 Apr 2020 07:29:36 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jTREw-003ZVU-6Y; Tue, 28 Apr 2020 17:29:38 +0300 Date: Tue, 28 Apr 2020 17:29:38 +0300 From: Andy Shevchenko To: Robin Murphy Cc: Michael Walle , linux-gpio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hwmon@vger.kernel.org, linux-pwm@vger.kernel.org, linux-watchdog@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Linus Walleij , Bartosz Golaszewski , Rob Herring , Jean Delvare , Guenter Roeck , Lee Jones , Thierry Reding , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Wim Van Sebroeck , Shawn Guo , Li Yang , Thomas Gleixner , Jason Cooper , Marc Zyngier , Mark Brown , Greg Kroah-Hartman Subject: Re: [PATCH v3 02/16] mfd: mfd-core: Don't overwrite the dma_mask of the child device Message-ID: <20200428142938.GX185537@smile.fi.intel.com> References: <20200423174543.17161-1-michael@walle.cc> <20200423174543.17161-3-michael@walle.cc> <20200428124548.GS185537@smile.fi.intel.com> <3cd3705a-4f48-6a46-e869-3ee11dc17323@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3cd3705a-4f48-6a46-e869-3ee11dc17323@arm.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Tue, Apr 28, 2020 at 02:06:20PM +0100, Robin Murphy wrote: > On 2020-04-28 1:45 pm, Andy Shevchenko wrote: > > On Thu, Apr 23, 2020 at 07:45:29PM +0200, Michael Walle wrote: > > > Commit cdfee5623290 ("driver core: initialize a default DMA mask for > > > platform device") initialize the DMA of a platform device. But if the > > > parent doesn't have a dma_mask set, for example if it's an I2C device, > > > the dma_mask of the child platform device will be set to zero again. > > > Which leads to many "DMA mask not set" warnings, if the MFD cell has the > > > of_compatible property set. > > > > I'm wondering why parent doesn't have it. > > Because the parent isn't on a DMA-capable bus, and thus really shouldn't > have a valid DMA configuration ever. Then how come a child is DMA capable? MFD takes a physical device node as a parent and creates one of several children with that device as a parent. DMA mask is a property of the device which *does DMA*. Obviously a child is not correct device for that. Where am I mistaken? > > I remember we have explicit patches in the past for buses such as PCI and AMBA > > to set default DMA mask for all physical devices on the respective bus, of > > course they can individually override it later. > > > > So, this seems to me a paper over the real issue (absence of default DMA mask > > where it's needed) and devices should explicitly define it if they disagree > > with default. > > > > If I'm wrong, you really need elaborate commit message much better. > > The problem here is that MFD children are created as platform devices > (regardless of what their parent is) and assigned an of_node, at which point > they look pretty much indistinguishable from SoC devices created by the > of_platform code, that *do* have to be assumed to be DMA-capable to prevent > ~90% of existing devicetrees from breaking. > > Of course the real fundamental issue is the platform bus itself, but it's > way too late to fix that :( I don't think it's an issue, rather in model you are describing. Or I miss something not so obvious. -- With Best Regards, Andy Shevchenko