Thread (36 messages) 36 messages, 4 authors, 2020-09-26

Re: a saner API for allocating DMA addressable pages v3

From: Christoph Hellwig <hch@lst.de>
Date: 2020-09-21 06:36:38
Also in: alsa-devel, linux-arm-kernel, linux-doc, linux-iommu, linux-media, linux-mips, linux-mm, linux-samsung-soc, linux-scsi, lkml, nouveau

Any comments?

Thomas: this should be identical to the git tree I gave you for mips
testing, and you add your tested-by (and reviewd-by tags where
applicable)?

Helge: for parisc this should effectively be the same as the first
version, but I've dropped the tested-by tags due to the reshuffle,
and chance you could retest it?

On Tue, Sep 15, 2020 at 05:51:04PM +0200, Christoph Hellwig wrote:
Hi all,

this series replaced the DMA_ATTR_NON_CONSISTENT flag to dma_alloc_attrs
with a separate new dma_alloc_pages API, which is available on all
platforms.  In addition to cleaning up the convoluted code path, this
ensures that other drivers that have asked for better support for
non-coherent DMA to pages with incurring bounce buffering over can finally
be properly supported.

As a follow up I plan to move the implementation of the
DMA_ATTR_NO_KERNEL_MAPPING flag over to this framework as well, given
that is also is a fundamentally non coherent allocation.  The replacement
for that flag would then return a struct page, as it is allowed to
actually return pages without a kernel mapping as the name suggested
(although most of the time they will actually have a kernel mapping..)

In addition to the conversions of the existing non-coherent DMA users,
I've also added a patch to convert the firewire ohci driver to use
the new dma_alloc_pages API.

The first patch is queued up for 5.9 in the media tree, but included here
for completeness.


A git tree is available here:

    git://git.infradead.org/users/hch/misc.git dma_alloc_pages

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dma_alloc_pages


Changes since v2:
 - fix up the patch reshuffle which wasn't quite correct
 - fix up a few commit messages

Changes since v1:
 - rebased on the latests dma-mapping tree, which merged many of the
   cleanups
 - fix an argument passing typo in 53c700, caught by sparse
 - rename a few macro arguments in 53c700
 - pass the right device to the DMA API in the lib82596 drivers
 - fix memory ownershiptransfers in sgiseeq
 - better document what a page in the direct kernel mapping means
 - split into dma_alloc_pages that returns a struct page and is in the
   direct mapping vs dma_alloc_noncoherent that can be vmapped
 - conver the firewire ohci driver to dma_alloc_pages

Diffstat:
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