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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 2AC48C10F25 for ; Wed, 11 Mar 2020 06:18:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E826220873 for ; Wed, 11 Mar 2020 06:18:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727480AbgCKGSJ (ORCPT ); Wed, 11 Mar 2020 02:18:09 -0400 Received: from verein.lst.de ([213.95.11.211]:57420 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725976AbgCKGSI (ORCPT ); Wed, 11 Mar 2020 02:18:08 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 5597968C4E; Wed, 11 Mar 2020 07:18:06 +0100 (CET) Date: Wed, 11 Mar 2020 07:18:06 +0100 From: Christoph Hellwig To: Michael Walle Cc: linux-kernel@vger.kernel.org, Lee Jones , Christoph Hellwig , Rob Herring , Robin Murphy , Russell King Subject: Re: [RFC PATCH] mfd: mfd-core: inherit only valid dma_masks/flags from parent Message-ID: <20200311061806.GB10902@lst.de> References: <20200310230935.23962-1-michael@walle.cc> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200310230935.23962-1-michael@walle.cc> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 11, 2020 at 12:09:35AM +0100, 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. > > There was also a thread [1] about this topic, but there seems to be no > conclusion. > > [1] https://www.spinics.net/lists/linux-renesas-soc/msg31581.html > > drivers/mfd/mfd-core.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c > index b9eb8f40c073..5d8ea5e8e93c 100644 > --- a/drivers/mfd/mfd-core.c > +++ b/drivers/mfd/mfd-core.c > @@ -139,9 +139,12 @@ 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->dev.dma_parms = parent->dma_parms; > - pdev->dev.coherent_dma_mask = parent->coherent_dma_mask; > + if (parent->dma_mask) > + pdev->dev.dma_mask = parent->dma_mask; > + if (parent->dma_parms) > + pdev->dev.dma_parms = parent->dma_parms; Both of these are pointers, and we can't just share them. You need to allocate storage for them and the allocate the values over.