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From: Christoph Hellwig <>
To: Mauro Carvalho Chehab <>,
	Thomas Bogendoerfer <>,
	"James E.J. Bottomley" <>,
	Joonyoung Shim <>,
	Seung-Woo Kim <>,
	Ben Skeggs <>,
	Marek Szyprowski <>,
	Tomasz Figa <>,
	Matt Porter <>,
Cc:,,,,,,,,, Stefan Richter <>,,,,
Subject: a saner API for allocating DMA addressable pages v2
Date: Mon, 14 Sep 2020 16:44:16 +0200	[thread overview]
Message-ID: <> (raw)

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.

I'm still a little unsure about the API naming, as alloc_pages sort of
implies a struct page return value, but we return a kernel virtual
address.  The other alternative would be to name the API
dma_alloc_noncoherent, but the whole non-coherent naming seems to put
people off.  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.

Note that I haven't carried over any Tested-by: tags for the noncoherent
allocation conversions as there was a bit of a patch reshuffle, but the
result should be the same.

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:// dma_alloc_pages


Changes since v1:
 - rebased on the latests dma-mapping tree, which merged many of the
 - 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

iommu mailing list

             reply	other threads:[~2020-09-14 14:47 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-14 14:44 Christoph Hellwig [this message]
2020-09-14 14:44 ` [PATCH 01/17] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT flag Christoph Hellwig
2020-09-14 14:44 ` [PATCH 02/17] mm: turn alloc_pages into an inline function Christoph Hellwig
2020-09-14 14:44 ` [PATCH 03/17] drm/exynos: stop setting DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2020-09-14 15:34   ` Sergei Shtylyov
2020-09-15  6:33     ` Christoph Hellwig
2020-09-14 14:44 ` [PATCH 04/17] drm/nouveau/gk20a: " Christoph Hellwig
2020-09-14 14:44 ` [PATCH 05/17] net/au1000-eth: stop using DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2020-09-14 14:44 ` [PATCH 06/17] lib82596: move DMA allocation into the callers of i82596_probe Christoph Hellwig
2020-09-14 14:44 ` [PATCH 07/17] 53c700: improve non-coherent DMA handling Christoph Hellwig
2020-09-14 15:20   ` James Bottomley
2020-09-15  6:27     ` Christoph Hellwig
2020-09-15 14:10       ` James Bottomley
2020-09-14 14:44 ` [PATCH 08/17] dma-mapping: add a new dma_alloc_noncoherent API Christoph Hellwig
2020-09-14 14:44 ` [PATCH 09/17] sgiwd93: convert to dma_alloc_noncoherent Christoph Hellwig
2020-09-14 14:44 ` [PATCH 10/17] hal2: " Christoph Hellwig
2020-09-14 14:44 ` [PATCH 11/17] sgiseeq: " Christoph Hellwig
2020-09-14 15:13   ` Matthew Wilcox
2020-09-15  6:32     ` Christoph Hellwig
2020-09-14 14:44 ` [PATCH 12/17] 53c700: " Christoph Hellwig
2020-09-14 14:44 ` [PATCH 13/17] dma-mapping: remove dma_cache_sync Christoph Hellwig
2020-09-14 14:44 ` [PATCH 14/17] dma-mapping: add a new dma_alloc_pages API Christoph Hellwig
2020-09-14 14:44 ` [PATCH 15/17] dma-mapping: add new {alloc, free}_noncoherent dma_map_ops methods Christoph Hellwig
2020-09-14 14:44 ` [PATCH 16/17] dma-iommu: implement ->alloc_noncoherent Christoph Hellwig
2020-09-14 14:44 ` [PATCH 17/17] firewire-ohci: use dma_alloc_pages Christoph Hellwig
2020-09-14 15:26 ` a saner API for allocating DMA addressable pages v2 Matthew Wilcox
2020-09-15  6:36   ` Christoph Hellwig

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