From: Christoph Hellwig <hch@lst.de>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Christoph Hellwig <hch@lst.de>,
Russell King <linux@armlinux.org.uk>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,"
<iommu@lists.linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] mmc: let the dma map ops handle bouncing
Date: Thu, 11 Apr 2019 16:34:30 +0200 [thread overview]
Message-ID: <20190411143430.GA17371@lst.de> (raw)
In-Reply-To: <CAPDyKFqHrvz_5taNTx7k6Skx=Ox+9XgQHHz0LZyr4QNV9orvRw@mail.gmail.com>
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.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Russell King <linux@armlinux.org.uk>,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,
" <iommu@lists.linux-foundation.org>,
Christoph Hellwig <hch@lst.de>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/2] mmc: let the dma map ops handle bouncing
Date: Thu, 11 Apr 2019 16:34:30 +0200 [thread overview]
Message-ID: <20190411143430.GA17371@lst.de> (raw)
Message-ID: <20190411143430.EUEY9oMzeIHIofrmi9BwyuMckDpCU3Y8rVBkC-8_0kI@z> (raw)
In-Reply-To: <CAPDyKFqHrvz_5taNTx7k6Skx=Ox+9XgQHHz0LZyr4QNV9orvRw@mail.gmail.com>
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.
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iommu@lists.linux-foundation.org
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next prev parent reply other threads:[~2019-04-11 14:34 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-11 7:09 get rid of dma_max_pfn Christoph Hellwig
2019-04-11 7:09 ` Christoph Hellwig
2019-04-11 7:09 ` [PATCH 1/2] mmc: let the dma map ops handle bouncing Christoph Hellwig
2019-04-11 7:09 ` Christoph Hellwig
2019-04-11 9:00 ` Ulf Hansson
2019-04-11 9:00 ` Ulf Hansson
2019-04-11 14:34 ` Christoph Hellwig [this message]
2019-04-11 14:34 ` Christoph Hellwig
2019-04-11 7:09 ` [PATCH 2/2] dma-mapping: remove dma_max_pfn Christoph Hellwig
2019-04-11 7:09 ` Christoph Hellwig
2019-06-25 9:20 get rid of dma_max_pfn Christoph Hellwig
2019-06-25 9:20 ` [PATCH 1/2] mmc: let the dma map ops handle bouncing Christoph Hellwig
2019-07-08 11:55 ` Ulf Hansson
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