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=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 8E153C10F27 for ; Wed, 11 Mar 2020 13:10:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58C1422464 for ; Wed, 11 Mar 2020 13:10:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=walle.cc header.i=@walle.cc header.b="jsXNM2wq" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729579AbgCKNKJ (ORCPT ); Wed, 11 Mar 2020 09:10:09 -0400 Received: from ssl.serverraum.org ([176.9.125.105]:40383 "EHLO ssl.serverraum.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729320AbgCKNKI (ORCPT ); Wed, 11 Mar 2020 09:10:08 -0400 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 03E7E23E68; Wed, 11 Mar 2020 14:10:04 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1583932205; 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=pAA7KgLyLRLoYnDJlQStIPFh8C+EewIWjpAD8ZGuqRA=; b=jsXNM2wqYJpN/1wVlSTmmSoTtG9YSiVhax7XZQR/7UJqJqTS5sAj7Y2xen4E2VaQBtwcrA XJi7rd1OOu2MMSB56DCfEXzdveqkfrLYpfu2CObTktWidvgJ94BF2rpIOhadyjI9PkLc/a pkR0//E1A/CIBWYoBz2kP58g8s+KEVc= MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 11 Mar 2020 14:10:04 +0100 From: Michael Walle To: Robin Murphy Cc: linux-kernel@vger.kernel.org, Lee Jones , Christoph Hellwig , Rob Herring , Russell King Subject: Re: [RFC PATCH] mfd: mfd-core: inherit only valid dma_masks/flags from parent In-Reply-To: <5f167c37-566f-bd62-b0fd-fdb7925c5afd@arm.com> References: <20200310230935.23962-1-michael@walle.cc> <5f167c37-566f-bd62-b0fd-fdb7925c5afd@arm.com> Message-ID: <68db76c663170817c223fcf779a92d28@walle.cc> X-Sender: michael@walle.cc User-Agent: Roundcube Webmail/1.3.10 X-Spamd-Bar: / X-Rspamd-Server: web X-Rspamd-Queue-Id: 03E7E23E68 X-Spamd-Result: default: False [-0.10 / 15.00]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; RCPT_COUNT_FIVE(0.00)[6]; DKIM_SIGNED(0.00)[]; NEURAL_HAM(-0.00)[-0.662]; RCVD_COUNT_ZERO(0.00)[0]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[] Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 2020-03-11 12:25, schrieb Robin Murphy: > On 2020-03-10 11:09 pm, Michael Walle wrote: >> Only copy the dma_masks and flags from the parent device, if the >> parent >> has a valid dma_mask/flags. Commit cdfee5623290 ("driver core: >> initialize a default DMA mask for platform device") initialize the DMA >> masks 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. >> >> [ 1.877937] sl28cpld-pwm sl28cpld-pwm: DMA mask not set >> [ 1.883282] sl28cpld-pwm sl28cpld-pwm.0: DMA mask not set >> [ 1.888795] sl28cpld-gpio sl28cpld-gpio: DMA mask not set >> >> Thus a MFD child should just inherit valid dma_masks and keep the >> platform default otherwise. >> >> Cc: Christoph Hellwig >> Cc: Rob Herring >> Cc: Robin Murphy >> Cc: Russell King >> Signed-off-by: Michael Walle >> --- >> >> Hi, >> >> I don't know if that is the correct way of handling things. Maybe I'm >> also doing something wrong in my driver, I had a look at other I2C MFD >> drivers but couldn't find a clue why they shouldn't have the same >> problem. > > The underlying issue is that about 99% of MFD children should not be > going through dma_configure() at all because their parent 'real' > device is not on a DMA-capable bus, but as they are platform devices > we are forced to give them the benefit of the doubt. For DT systems > the only vaguely-reasonable heuristic to distinguish between > "platform" meaning "SoC memory-mapped device" and "platform" meaning > "random crap made up by Linux" is whether the device has a populated > OF node, but MFD's trick of hanging the parent device's OF node onto > its synthesised children kicks a hole right through even that. Thanks for the explanation. > Modulo any other concerns with the existing code, does the change > below make things work the way you want? It's still a bit of a bodge, > but short of invasive large-scale changes with bus types I don't see a > way to do the 'right' thing :/ > > Robin. > > ----->8----- > diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c > index f5a73af60dd4..1e4a6e8bd630 100644 > --- a/drivers/mfd/mfd-core.c > +++ b/drivers/mfd/mfd-core.c > @@ -138,7 +138,7 @@ static int mfd_add_device(struct device *parent, > int id, > > pdev->dev.parent = parent; > pdev->dev.type = &mfd_dev_type; > - pdev->dev.dma_mask = parent->dma_mask; > + pdev->dma_mask = parent->dma_mask ? *parent->dma_mask : 0; That works. -michael > pdev->dev.dma_parms = parent->dma_parms; > pdev->dev.coherent_dma_mask = parent->coherent_dma_mask;