From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Linux IOMMU <iommu@lists.linux-foundation.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Takashi Iwai <tiwai@suse.de>, Robin Murphy <robin.murphy@arm.com>,
Michal Simek <monstr@monstr.eu>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
linux-m68k <linux-m68k@lists.linux-m68k.org>,
Parisc List <linux-parisc@vger.kernel.org>,
Linux-sh list <linux-sh@vger.kernel.org>,
linux-xtensa@linux-xtensa.org,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/5] dma-mapping: provide a better default ->get_required_mask
Date: Mon, 29 Jul 2019 11:57:19 +0200 [thread overview]
Message-ID: <CAMuHMdUBPj8AVSuDwaBB_4gRD6k7vzo0WAFJEkTUbxSw31bzUg@mail.gmail.com> (raw)
In-Reply-To: <20190725063401.29904-5-hch@lst.de>
Hi Christoph,
On Thu, Jul 25, 2019 at 8:35 AM Christoph Hellwig <hch@lst.de> wrote:
> Most dma_map_ops instances are IOMMUs that work perfectly fine in 32-bits
> of IOVA space, and the generic direct mapping code already provides its
> own routines that is intelligent based on the amount of memory actually
> present. Wire up the dma-direct routine for the ARM direct mapping code
> as well, and otherwise default to the constant 32-bit mask. This way
> we only need to override it for the occasional odd IOMMU that requires
> 64-bit IOVA support, or IOMMU drivers that are more efficient if they
> can fall back to the direct mapping.
As I know you like diving into cans of worms ;-)
Does 64-bit IOVA support actually work in general? Or only on 64-bit
platforms, due to dma_addr_t to unsigned long truncation on 32-bit?
https://lore.kernel.org/linux-renesas-soc/CAMuHMdWkQ918Y61tMJbHEu29AGLEyNwbvZbSBB-RRH7YYUNRcA@mail.gmail.com/
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2019-07-29 9:57 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-25 6:33 remove default fallbacks in dma_map_ops Christoph Hellwig
2019-07-25 6:33 ` [PATCH 1/5] m68knommu: add a pgprot_noncached stub Christoph Hellwig
2019-07-25 6:33 ` [PATCH 2/5] dma-mapping: move the dma_get_sgtable API comments from arm to common code Christoph Hellwig
2019-07-25 6:33 ` [PATCH 3/5] dma-mapping: explicitly wire up ->mmap and ->get_sgtable Christoph Hellwig
2019-07-25 6:34 ` [PATCH 4/5] dma-mapping: provide a better default ->get_required_mask Christoph Hellwig
2019-07-29 9:57 ` Geert Uytterhoeven [this message]
2019-07-30 6:26 ` Christoph Hellwig
2019-07-25 6:34 ` [PATCH 5/5] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP Christoph Hellwig
2019-08-02 7:03 ` Christoph Hellwig
2019-08-02 8:24 ` Takashi Iwai
2019-08-03 10:30 ` Christoph Hellwig
2019-08-03 11:22 ` Takashi Iwai
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