From: Tomasz Figa <tfiga@chromium.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Ezequiel Garcia <ezequiel@collabora.com>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
linux-usb@vger.kernel.org,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,"
<linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
"Matwey V. Kornilov" <matwey@sai.msu.ru>,
Alan Stern <stern@rowland.harvard.edu>,
kernel@collabora.com, keiichiw@chromium.org
Subject: Re: [RFC 2/3] USB: core: Add non-coherent buffer allocation helpers
Date: Wed, 31 Oct 2018 10:55:23 +0900 [thread overview]
Message-ID: <CAAFQd5BjGkJf-Yz3ixiCjCaoeQJKKXbF41JyEvrm1DQ6uNnBrQ@mail.gmail.com> (raw)
In-Reply-To: <CAAFQd5DhFr8ywjc41oK9q+zZXH9zsOKh_7DxWmjzcE0+5Q3hGA@mail.gmail.com>
Hi Christoph and everyone,
On Fri, Aug 31, 2018 at 3:51 PM Tomasz Figa <tfiga@chromium.org> wrote:
>
> On Fri, Aug 31, 2018 at 2:50 PM Christoph Hellwig <hch@infradead.org> wrote:
> >
> > On Thu, Aug 30, 2018 at 07:11:35PM -0300, Ezequiel Garcia wrote:
> > > On Thu, 2018-08-30 at 10:58 -0700, Christoph Hellwig wrote:
> > > > Please don't introduce new DMA_ATTR_NON_CONSISTENT users, it is
> > > > a rather horrible interface, and I plan to kill it off rather sooner
> > > > than later. I plan to post some patches for a better interface
> > > > that can reuse the normal dma_sync_single_* interfaces for ownership
> > > > transfers. I can happily include usb in that initial patch set based
> > > > on your work here if that helps.
> > >
> > > Please do. Until we have proper allocators that go thru the DMA API,
> > > drivers will have to kmalloc the USB transfer buffers, and have
> > > streaming mappings. Which in turns mean not using IOMMU or CMA.
> >
> > dma_map_page will of course use the iommu.
>
> Sure, dma_map*() will, but using kmalloc() defeats (half of) the
> purpose of it, since contiguous memory would be allocated
> unnecessarily, risking failures due to fragmentation.
Have we reached a conclusion here?
It sounds like it's a quite significant problem, at least for some of
the camera (media) devices over there and there are people interested
in solving it, so all we need here is a conclusion on how to do it. :)
Best regards,
Tomasz
WARNING: multiple messages have this Message-ID (diff)
From: Tomasz Figa <tfiga@chromium.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Ezequiel Garcia <ezequiel@collabora.com>,
Linux Media Mailing List <linux-media@vger.kernel.org>,
linux-usb@vger.kernel.org,
"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
Joerg Roedel <joro@8bytes.org>,"
<linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
"Matwey V. Kornilov" <matwey@sai.msu.ru>,
Alan Stern <stern@rowland.harvard.edu>,
kernel@collabora.com, keiichiw@chromium.org
Subject: [RFC,2/3] USB: core: Add non-coherent buffer allocation helpers
Date: Wed, 31 Oct 2018 10:55:23 +0900 [thread overview]
Message-ID: <CAAFQd5BjGkJf-Yz3ixiCjCaoeQJKKXbF41JyEvrm1DQ6uNnBrQ@mail.gmail.com> (raw)
Hi Christoph and everyone,
On Fri, Aug 31, 2018 at 3:51 PM Tomasz Figa <tfiga@chromium.org> wrote:
>
> On Fri, Aug 31, 2018 at 2:50 PM Christoph Hellwig <hch@infradead.org> wrote:
> >
> > On Thu, Aug 30, 2018 at 07:11:35PM -0300, Ezequiel Garcia wrote:
> > > On Thu, 2018-08-30 at 10:58 -0700, Christoph Hellwig wrote:
> > > > Please don't introduce new DMA_ATTR_NON_CONSISTENT users, it is
> > > > a rather horrible interface, and I plan to kill it off rather sooner
> > > > than later. I plan to post some patches for a better interface
> > > > that can reuse the normal dma_sync_single_* interfaces for ownership
> > > > transfers. I can happily include usb in that initial patch set based
> > > > on your work here if that helps.
> > >
> > > Please do. Until we have proper allocators that go thru the DMA API,
> > > drivers will have to kmalloc the USB transfer buffers, and have
> > > streaming mappings. Which in turns mean not using IOMMU or CMA.
> >
> > dma_map_page will of course use the iommu.
>
> Sure, dma_map*() will, but using kmalloc() defeats (half of) the
> purpose of it, since contiguous memory would be allocated
> unnecessarily, risking failures due to fragmentation.
Have we reached a conclusion here?
It sounds like it's a quite significant problem, at least for some of
the camera (media) devices over there and there are people interested
in solving it, so all we need here is a conclusion on how to do it. :)
Best regards,
Tomasz
WARNING: multiple messages have this Message-ID (diff)
From: tfiga@chromium.org (Tomasz Figa)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC 2/3] USB: core: Add non-coherent buffer allocation helpers
Date: Wed, 31 Oct 2018 10:55:23 +0900 [thread overview]
Message-ID: <CAAFQd5BjGkJf-Yz3ixiCjCaoeQJKKXbF41JyEvrm1DQ6uNnBrQ@mail.gmail.com> (raw)
In-Reply-To: <CAAFQd5DhFr8ywjc41oK9q+zZXH9zsOKh_7DxWmjzcE0+5Q3hGA@mail.gmail.com>
Hi Christoph and everyone,
On Fri, Aug 31, 2018 at 3:51 PM Tomasz Figa <tfiga@chromium.org> wrote:
>
> On Fri, Aug 31, 2018 at 2:50 PM Christoph Hellwig <hch@infradead.org> wrote:
> >
> > On Thu, Aug 30, 2018 at 07:11:35PM -0300, Ezequiel Garcia wrote:
> > > On Thu, 2018-08-30 at 10:58 -0700, Christoph Hellwig wrote:
> > > > Please don't introduce new DMA_ATTR_NON_CONSISTENT users, it is
> > > > a rather horrible interface, and I plan to kill it off rather sooner
> > > > than later. I plan to post some patches for a better interface
> > > > that can reuse the normal dma_sync_single_* interfaces for ownership
> > > > transfers. I can happily include usb in that initial patch set based
> > > > on your work here if that helps.
> > >
> > > Please do. Until we have proper allocators that go thru the DMA API,
> > > drivers will have to kmalloc the USB transfer buffers, and have
> > > streaming mappings. Which in turns mean not using IOMMU or CMA.
> >
> > dma_map_page will of course use the iommu.
>
> Sure, dma_map*() will, but using kmalloc() defeats (half of) the
> purpose of it, since contiguous memory would be allocated
> unnecessarily, risking failures due to fragmentation.
Have we reached a conclusion here?
It sounds like it's a quite significant problem, at least for some of
the camera (media) devices over there and there are people interested
in solving it, so all we need here is a conclusion on how to do it. :)
Best regards,
Tomasz
next prev parent reply other threads:[~2018-10-31 1:55 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 17:20 [RFC 0/3] Introduce usb_{alloc,free}_noncoherent API Ezequiel Garcia
2018-08-30 17:20 ` Ezequiel Garcia
2018-08-30 17:20 ` [RFC 1/3] HACK: ARM: dma-mapping: Get writeback memory for non-consistent mappings Ezequiel Garcia
2018-08-30 17:20 ` Ezequiel Garcia
2018-08-30 17:20 ` [RFC,1/3] " Ezequiel Garcia
2018-08-30 17:20 ` [RFC 2/3] USB: core: Add non-coherent buffer allocation helpers Ezequiel Garcia
2018-08-30 17:20 ` Ezequiel Garcia
2018-08-30 17:20 ` [RFC,2/3] " Ezequiel Garcia
2018-08-30 17:58 ` [RFC 2/3] " Christoph Hellwig
2018-08-30 17:58 ` Christoph Hellwig
2018-08-30 17:58 ` [RFC,2/3] " Christoph Hellwig
2018-08-30 22:11 ` [RFC 2/3] " Ezequiel Garcia
2018-08-30 22:11 ` Ezequiel Garcia
2018-08-30 22:11 ` [RFC,2/3] " Ezequiel Garcia
2018-08-31 5:50 ` [RFC 2/3] " Christoph Hellwig
2018-08-31 5:50 ` Christoph Hellwig
2018-08-31 5:50 ` [RFC,2/3] " Christoph Hellwig
2018-08-31 6:51 ` [RFC 2/3] " Tomasz Figa
2018-08-31 6:51 ` Tomasz Figa
2018-08-31 6:51 ` [RFC,2/3] " Tomasz Figa
2018-10-31 1:55 ` Tomasz Figa [this message]
2018-10-31 1:55 ` [RFC 2/3] " Tomasz Figa
2018-10-31 1:55 ` [RFC,2/3] " Tomasz Figa
2018-08-30 17:20 ` [RFC 3/3] stk1160: Use non-coherent buffers for USB transfers Ezequiel Garcia
2018-08-30 17:20 ` Ezequiel Garcia
2018-08-30 17:20 ` [RFC,3/3] " Ezequiel Garcia
2018-08-30 17:59 ` [RFC 3/3] " Christoph Hellwig
2018-08-30 17:59 ` Christoph Hellwig
2018-08-30 17:59 ` [RFC,3/3] " Christoph Hellwig
2018-09-07 8:54 ` [RFC 3/3] " Tomasz Figa
2018-09-07 8:54 ` Tomasz Figa
2018-09-07 8:54 ` [RFC,3/3] " Tomasz Figa
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