From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C41F91A08BC; Tue, 27 Aug 2024 12:19:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724761160; cv=none; b=Jvd69gsN/OtqLAZau6Imr0weTyJT4PVoYrNg9m6uKq8Z6S+HnNMerW0WAVcNlguwc48R/w7Seqm6NzAaqXdEq5yFqk++rRVmDeUuy1ixocoIu9VHZnhCW5tyPWJM5vJ2ahYD9b5wEDywrBcs2Dsy2dKYcpYQ4HdUNvcr+pZKa8c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724761160; c=relaxed/simple; bh=PY/odrZ7HFMDFloiTo+2Oa6vUtHjnrzFME+/EnQwvEM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=cPLJ1L3C7RjbXxvnrTUI3w+PQguu6WaWmK+n5wB5+Zg8MMN3xPdkelAx1at2sit9xTdjbBNycx9Gq9JLcB5UMNPzdJDM4i6CvIaNeENrk+m/6C+zgdOD5aMwVLNM969fjmm4uJ6VQtFcG+f62qq2eBw20mBXTBd01ehpPIKEP4o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6D0DCDA7; Tue, 27 Aug 2024 05:19:43 -0700 (PDT) Received: from [10.1.196.40] (e121345-lin.cambridge.arm.com [10.1.196.40]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 185FF3F762; Tue, 27 Aug 2024 05:19:14 -0700 (PDT) Message-ID: <92ebdc16-7938-462a-bb0e-4d5d368c5eb1@arm.com> Date: Tue, 27 Aug 2024 13:19:13 +0100 Precedence: bulk X-Mailing-List: linux-mmc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] scsi: check that busses support the DMA API before setting dma parameters To: Christoph Hellwig , iommu@lists.linux.dev Cc: "Martin K. Petersen" , Marek Szyprowski , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, linux-media@vger.kernel.org, linux-mmc@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-hyperv@vger.kernel.org, netdev@vger.kernel.org References: <20240824034925.1163244-1-hch@lst.de> <20240824034925.1163244-2-hch@lst.de> From: Robin Murphy Content-Language: en-GB In-Reply-To: <20240824034925.1163244-2-hch@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 24/08/2024 4:49 am, Christoph Hellwig wrote: > We'll start throwing warnings soon when dma_set_seg_boundary and > dma_set_max_seg_size are called on devices for buses that don't fully > support the DMA API. Prepare for that by making the calls in the SCSI > midlayer conditional. Just thinking ahead, might it be worth a logical "are SG segment limits relevant?" wrapper around the dev->dma_parms reference? Not a big deal for now if we think this site is the only user, so either way, Reviewed-by: Robin Murphy > Signed-off-by: Christoph Hellwig > --- > drivers/scsi/scsi_lib.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index 3958a6d14bf457..7f0394c4492033 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -1988,8 +1988,15 @@ void scsi_init_limits(struct Scsi_Host *shost, struct queue_limits *lim) > if (shost->no_highmem) > lim->features |= BLK_FEAT_BOUNCE_HIGH; > > - dma_set_seg_boundary(dev, shost->dma_boundary); > - dma_set_max_seg_size(dev, shost->max_segment_size); > + /* > + * Propagate the DMA formation properties to the dma-mapping layer as > + * a courtesy service to the LLDDs. This needs to check that the buses > + * actually support the DMA API first, though. > + */ > + if (dev->dma_parms) { > + dma_set_seg_boundary(dev, shost->dma_boundary); > + dma_set_max_seg_size(dev, shost->max_segment_size); > + } > } > EXPORT_SYMBOL_GPL(scsi_init_limits); >