From: Marek Szyprowski <m.szyprowski@samsung.com>
To: Christoph Hellwig <hch@lst.de>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
Joonyoung Shim <jy0922.shim@samsung.com>,
Seung-Woo Kim <sw0312.kim@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
Ben Skeggs <bskeggs@redhat.com>, Pawel Osciak <pawel@osciak.com>,
Matt Porter <mporter@kernel.crashing.org>,
iommu@lists.linux-foundation.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
alsa-devel@alsa-project.org, linux-samsung-soc@vger.kernel.org,
linux-ia64@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-parisc@vger.kernel.org, linux-doc@vger.kernel.org,
nouveau@lists.freedesktop.org, linux-kernel@vger.kernel.org,
linux-nvme@lists.infradead.org, linux-mips@vger.kernel.org,
linux-mm@kvack.org, netdev@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-media@vger.kernel.org
Subject: Re: a saner API for allocating DMA addressable pages
Date: Tue, 25 Aug 2020 13:30:41 +0200 [thread overview]
Message-ID: <8fa1ce36-c783-1a02-6890-211eb504a33b@samsung.com> (raw)
In-Reply-To: <20200819065555.1802761-1-hch@lst.de>
Hi Christoph,
On 19.08.2020 08:55, Christoph Hellwig wrote:
> 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
> the last three patches also convert the DMA coherent allocations in
> the NVMe driver to use this new framework through a dmapool addition.
> This was both to give me a good testing vehicle, but also because it
> should speed up the NVMe driver on platforms with non-coherent DMA
> nicely, without a downside on platforms with cache coherent DMA.
I really wonder what is the difference between this new API and
alloc_pages(GFP_DMA, n). Is this API really needed? I thought that this
is legacy thing to be removed one day...
Maybe it would make more sense to convert the few remaining drivers to
regular dma_map_page()/dma_sync_*()/dma_unmap_page() or have I missed
something?
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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next prev parent reply other threads:[~2020-08-25 11:30 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200819065610eucas1p2fde88e81917071b1888e7cc01ba0f298@eucas1p2.samsung.com>
2020-08-19 6:55 ` a saner API for allocating DMA addressable pages Christoph Hellwig
2020-08-19 6:55 ` [PATCH 01/28] mm: turn alloc_pages into an inline function Christoph Hellwig
2020-08-19 6:55 ` [PATCH 02/28] drm/exynos: stop setting DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2020-08-19 6:55 ` [PATCH 03/28] drm/nouveau/gk20a: " Christoph Hellwig
2020-08-19 6:55 ` [PATCH 04/28] net/au1000-eth: stop using DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2020-08-19 6:55 ` [PATCH 05/28] media/v4l2: remove V4L2-FLAG-MEMORY-NON-CONSISTENT Christoph Hellwig
2020-08-19 11:16 ` Tomasz Figa
2020-08-19 11:51 ` Robin Murphy
2020-08-19 12:49 ` Tomasz Figa
2020-08-19 13:57 ` Christoph Hellwig
2020-08-19 14:11 ` Tomasz Figa
2020-08-20 4:45 ` Christoph Hellwig
2020-08-20 10:09 ` Tomasz Figa
2020-08-20 16:51 ` Christoph Hellwig
2020-08-19 14:07 ` Robin Murphy
2020-08-19 14:22 ` Tomasz Figa
2020-08-20 4:52 ` Christoph Hellwig
2020-08-20 5:02 ` Christoph Hellwig
2020-08-20 10:24 ` Tomasz Figa
2020-08-20 16:52 ` Christoph Hellwig
2020-08-20 17:41 ` Tomasz Figa
2020-08-19 13:54 ` Christoph Hellwig
2020-08-19 13:57 ` Tomasz Figa
2020-08-20 4:43 ` Christoph Hellwig
2020-08-20 5:20 ` Christoph Hellwig
2020-08-20 10:05 ` Tomasz Figa
2020-08-20 16:54 ` Christoph Hellwig
2020-08-20 17:33 ` Tomasz Figa
2020-09-01 11:06 ` Christoph Hellwig
2020-09-01 15:02 ` Tomasz Figa
2020-08-19 6:55 ` [PATCH 06/28] lib82596: move DMA allocation into the callers of i82596_probe Christoph Hellwig
2020-09-01 13:29 ` Thomas Bogendoerfer
2020-08-19 6:55 ` [PATCH 07/28] 53c700: improve non-coherent DMA handling Christoph Hellwig
2020-09-01 14:52 ` James Bottomley
2020-09-01 15:05 ` Matthew Wilcox
2020-09-01 15:22 ` James Bottomley
2020-09-01 16:21 ` Helge Deller
2020-09-01 16:41 ` Helge Deller
2020-09-01 16:53 ` Matthew Wilcox
2020-09-02 15:00 ` Helge Deller
2020-08-19 6:55 ` [PATCH 08/28] MIPS: make dma_sync_*_for_cpu a little less overzealous Christoph Hellwig
2020-09-01 13:53 ` Thomas Bogendoerfer
2020-08-19 6:55 ` [PATCH 09/28] MIPS/jazzdma: remove the unused vdma_remap function Christoph Hellwig
2020-09-01 13:49 ` Thomas Bogendoerfer
2020-08-19 6:55 ` [PATCH 10/28] MIPS/jazzdma: decouple from dma-direct Christoph Hellwig
2020-09-01 13:49 ` Thomas Bogendoerfer
2020-08-19 6:55 ` [PATCH 11/28] dma-mapping: add (back) arch_dma_mark_clean for ia64 Christoph Hellwig
2020-08-19 6:55 ` [PATCH 12/28] dma-direct: remove dma_direct_{alloc,free}_pages Christoph Hellwig
2020-08-19 6:55 ` [PATCH 13/28] dma-direct: lift gfp_t manipulation out of__dma_direct_alloc_pages Christoph Hellwig
2020-08-19 6:55 ` [PATCH 14/28] dma-direct: use phys_to_dma_direct in dma_direct_alloc Christoph Hellwig
2020-08-19 6:55 ` [PATCH 15/28] dma-direct: remove __dma_to_phys Christoph Hellwig
2020-08-19 6:55 ` [PATCH 16/28] dma-direct: rename and cleanup __phys_to_dma Christoph Hellwig
2020-08-19 6:55 ` [PATCH 17/28] dma-mapping: move dma_common_{mmap, get_sgtable} out of mapping.c Christoph Hellwig
2020-08-19 6:55 ` [PATCH 18/28] dma-mapping: move the dma_declare_coherent_memory documentation Christoph Hellwig
2020-08-19 6:55 ` [PATCH 19/28] dma-mapping: replace DMA_ATTR_NON_CONSISTENT with dma_{alloc, free}_pages Christoph Hellwig
2020-08-19 15:03 ` Tomasz Figa
2020-08-20 5:15 ` Christoph Hellwig
2020-08-19 6:55 ` [PATCH 20/28] sgiwd93: convert from dma_cache_sync to dma_sync_single_for_device Christoph Hellwig
2020-08-19 6:55 ` [PATCH 21/28] hal2: " Christoph Hellwig
2020-08-19 6:55 ` [PATCH 22/28] sgiseeq: " Christoph Hellwig
2020-09-01 15:22 ` Thomas Bogendoerfer
2020-09-01 17:12 ` Thomas Bogendoerfer
2020-09-01 17:16 ` Christoph Hellwig
2020-09-01 17:38 ` Thomas Bogendoerfer
2020-09-02 21:38 ` Thomas Bogendoerfer
2020-09-03 8:42 ` Christoph Hellwig
2020-09-03 8:43 ` Christoph Hellwig
2020-09-03 8:46 ` Christoph Hellwig
2020-08-19 6:55 ` [PATCH 23/28] lib82596: " Christoph Hellwig
2020-08-19 6:55 ` [PATCH 24/28] 53c700: " Christoph Hellwig
2020-08-19 6:55 ` [PATCH 25/28] dma-mapping: remove dma_cache_sync Christoph Hellwig
2020-08-19 6:55 ` [PATCH 26/28] dmapool: add dma_alloc_pages support Christoph Hellwig
2020-08-19 6:55 ` [PATCH 27/28] nvme-pci: fix PRP pool size Christoph Hellwig
2020-08-19 6:55 ` [PATCH 28/28] nvme-pci: use dma_alloc_pages backed dmapools Christoph Hellwig
2020-08-25 11:30 ` Marek Szyprowski [this message]
2020-08-25 13:26 ` a saner API for allocating DMA addressable pages Christoph Hellwig
2020-08-29 9:46 ` Helge Deller
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