From: Christoph Hellwig <hch@infradead.org>
To: Vladimir Kondratiev <Vladimir.Kondratiev@mobileye.com>
Cc: Christoph Hellwig <hch@infradead.org>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH] riscv: make ZONE_DMA32 optional
Date: Mon, 23 Sep 2024 23:39:20 -0700 [thread overview]
Message-ID: <ZvJemFN1qdvi8qo-@infradead.org> (raw)
In-Reply-To: <VI1PR09MB233391A7544336FBD06303CE946E2@VI1PR09MB2333.eurprd09.prod.outlook.com>
On Sun, Sep 22, 2024 at 10:06:59AM +0000, Vladimir Kondratiev wrote:
> This is the whole point - there are platforms where you can't allocate 32-bit
> dma-able memory.
Ugg. They will be broke for all kinds of devices (plug in PCIe devices
IP IP blocks).
> Unless there's IOMMU or some platform specific tricks,
> DMA address is same as physical address.
Well, that's where the usual platform specific trick is, as the
platforms with high DRAM either have a mapping between physical
and DMA range (see the dma_ranges concept in the DMA and OF code)
or a mirror of the higher addresses. Or very rarely (e.g. sparc)
a required IOMMU that is always used.
next prev parent reply other threads:[~2024-09-24 6:39 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-27 11:36 Vladimir Kondratiev
2024-08-27 23:10 ` Drew Fustini
2024-09-20 8:58 ` Palmer Dabbelt
2024-09-20 13:18 ` Drew Fustini
2024-09-23 9:46 ` Ben Dooks
2024-09-20 14:04 ` Christoph Hellwig
2024-09-22 10:06 ` Vladimir Kondratiev
2024-09-24 6:39 ` Christoph Hellwig [this message]
2024-09-30 9:55 ` Alexandre Ghiti
2024-10-06 10:44 ` Vladimir Kondratiev
2024-10-06 10:55 ` [PATCH v1] " Vladimir Kondratiev
2024-10-06 22:58 ` Drew Fustini
2024-10-07 5:41 ` Christoph Hellwig
2024-10-07 6:17 ` Vladimir Kondratiev
2024-10-07 6:22 ` Christoph Hellwig
2024-10-07 11:39 ` Nick Kossifidis
2024-10-07 13:03 ` Vladimir Kondratiev
2024-10-07 12:17 ` [PATCH] " Ben Dooks
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