From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 1/2] mmc: let the dma map ops handle bouncing Date: Thu, 11 Apr 2019 16:34:30 +0200 Message-ID: <20190411143430.GA17371@lst.de> References: <20190411070948.29564-1-hch@lst.de> <20190411070948.29564-2-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Ulf Hansson Cc: Christoph Hellwig , Russell King , "linux-mmc@vger.kernel.org" , Linux ARM , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Linux Kernel Mailing List List-Id: iommu@lists.linux-foundation.org On Thu, Apr 11, 2019 at 11:00:56AM +0200, Ulf Hansson wrote: > > blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, mq->queue); > > if (mmc_can_erase(card)) > > mmc_queue_setup_discard(mq->queue, card); > > > > - blk_queue_bounce_limit(mq->queue, limit); > > + if (!mmc_dev(host)->dma_mask || !*mmc_dev(host)->dma_mask) > > + blk_queue_bounce_limit(mq->queue, BLK_BOUNCE_HIGH); > > So this means we are not going to set a bounce limit for the queue, in > case we have a dma mask. > > Why isn't that needed no more? Whats has changed? On most architectures it was never needed, the major hold out was x86-32 with PAE. In general the dma_mask tells the DMA API layer what is supported, and if the physical addressing doesn't support that it has to use bounce buffering like swiotlb (or dmabounce on arm32). A couple month ago I finally fixes x86-32 to also properly set up swiotlb, and remove the block layerer bounce buffering that wasn't for highmem (which is about having a kernel mapping, not addressing), and ISA DMA (which is not handled like everything else, but we'll get there). But for some reason I missed mmc back then, so mmc right now is the only remaining user of address based block layer bouncing. 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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 CFEDBC10F13 for ; Thu, 11 Apr 2019 14:35:36 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A2E57206BA for ; Thu, 11 Apr 2019 14:35:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2E57206BA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 69297241D; Thu, 11 Apr 2019 14:35:36 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id CA8CE23F1 for ; Thu, 11 Apr 2019 14:34:44 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from newverein.lst.de (verein.lst.de [213.95.11.211]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 5D76CF4 for ; Thu, 11 Apr 2019 14:34:44 +0000 (UTC) Received: by newverein.lst.de (Postfix, from userid 2407) id 150ED68AFE; Thu, 11 Apr 2019 16:34:31 +0200 (CEST) Date: Thu, 11 Apr 2019 16:34:30 +0200 From: Christoph Hellwig To: Ulf Hansson Subject: Re: [PATCH 1/2] mmc: let the dma map ops handle bouncing Message-ID: <20190411143430.GA17371@lst.de> References: <20190411070948.29564-1-hch@lst.de> <20190411070948.29564-2-hch@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Cc: "linux-mmc@vger.kernel.org" , Linux Kernel Mailing List , Russell King , "list@263.net:IOMMU DRIVERS , Joerg Roedel , " , Christoph Hellwig , Linux ARM X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org Message-ID: <20190411143430.EUEY9oMzeIHIofrmi9BwyuMckDpCU3Y8rVBkC-8_0kI@z> On Thu, Apr 11, 2019 at 11:00:56AM +0200, Ulf Hansson wrote: > > blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, mq->queue); > > if (mmc_can_erase(card)) > > mmc_queue_setup_discard(mq->queue, card); > > > > - blk_queue_bounce_limit(mq->queue, limit); > > + if (!mmc_dev(host)->dma_mask || !*mmc_dev(host)->dma_mask) > > + blk_queue_bounce_limit(mq->queue, BLK_BOUNCE_HIGH); > > So this means we are not going to set a bounce limit for the queue, in > case we have a dma mask. > > Why isn't that needed no more? Whats has changed? On most architectures it was never needed, the major hold out was x86-32 with PAE. In general the dma_mask tells the DMA API layer what is supported, and if the physical addressing doesn't support that it has to use bounce buffering like swiotlb (or dmabounce on arm32). A couple month ago I finally fixes x86-32 to also properly set up swiotlb, and remove the block layerer bounce buffering that wasn't for highmem (which is about having a kernel mapping, not addressing), and ISA DMA (which is not handled like everything else, but we'll get there). But for some reason I missed mmc back then, so mmc right now is the only remaining user of address based block layer bouncing. _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu