From: Grant Grundler <grundler@parisc-linux.org>
To: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: yinghai@kernel.org, grundler@parisc-linux.org, matthew@wil.cx,
jbarnes@virtuousgeek.org, mingo@elte.hu, tglx@linutronix.de,
hpa@zytor.com, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH] pci: print out DMA mask info
Date: Fri, 10 Oct 2008 16:45:08 -0600 [thread overview]
Message-ID: <20081010224508.GB28369@colo.lackof.org> (raw)
In-Reply-To: <20081010114003X.fujita.tomonori@lab.ntt.co.jp>
On Fri, Oct 10, 2008 at 11:40:56AM +0900, FUJITA Tomonori wrote:
> IIRC, except for one SGI architecture, coherent_dma_mask is
> meaningless, dma_mask is always equal to coherent_dma_mask.
Not correct. Several PCI-X devices can only do 32-bit DMA to control
data but can do 64-bit DMA for payload data. I don't have the list off
the top of my head but that is the origin of coherent DMA mask.
> Lots of
> IOMMU implementations ignore coherent_dma_mask and use dma_mask for
> alloc_coherent().
That sounds like a bug. And I don't think it's "lots".
> Some drivers don't set up coherent_dma_mask.
They probably should. Current default is 32-bits for PCI devices.
> Theoretically, we need to fix this but it doesn't cause any
> problem. That's why nobody cares about it, I guess.
Agreed - for the "supported" configurations, it works.
hth,
grant
next prev parent reply other threads:[~2008-10-10 22:45 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-10-08 23:02 Yinghai Lu
2008-10-09 21:18 ` Grant Grundler
2008-10-09 21:27 ` Yinghai Lu
2008-10-09 21:35 ` Matthew Wilcox
2008-10-09 21:51 ` Yinghai Lu
2008-10-09 22:55 ` Grant Grundler
2008-10-09 23:05 ` Yinghai Lu
2008-10-10 2:40 ` FUJITA Tomonori
2008-10-10 4:56 ` Yinghai Lu
2008-10-10 6:08 ` FUJITA Tomonori
2008-10-10 6:32 ` Yinghai Lu
2008-10-10 7:32 ` FUJITA Tomonori
2008-10-12 7:16 ` Grant Grundler
2008-10-10 22:45 ` Grant Grundler [this message]
2008-10-14 6:50 ` FUJITA Tomonori
2008-10-12 7:11 ` Grant Grundler
2008-10-23 1:45 ` [PATCH] pci: show dma_mask bits in /sys Yinghai Lu
2008-10-23 3:28 ` Matthew Wilcox
2008-10-23 4:19 ` Yinghai Lu
2008-10-23 6:44 ` Grant Grundler
2008-10-23 8:38 ` Rolf Eike Beer
2008-10-23 15:39 ` Greg KH
2008-10-23 18:37 ` H. Peter Anvin
2008-10-23 19:36 ` Grant Grundler
2008-10-23 19:49 ` Greg KH
2008-10-24 10:50 ` Andi Kleen
2008-11-01 17:10 ` Grant Grundler
2008-10-23 6:48 ` Grant Grundler
2008-10-23 6:51 ` Yinghai Lu
2008-10-23 19:28 ` Grant Grundler
2008-10-10 2:40 ` [PATCH] pci: print out DMA mask info FUJITA Tomonori
2008-10-10 2:59 ` FUJITA Tomonori
2008-10-10 2:40 ` FUJITA Tomonori
2008-10-10 15:48 ` Jesse Barnes
2008-10-10 16:19 ` Yinghai Lu
2008-10-10 16:28 ` Jesse Barnes
2008-10-10 16:33 ` Matthew Wilcox
2008-10-10 16:46 ` Yinghai Lu
2008-10-10 17:12 ` Matthew Wilcox
2008-10-10 17:18 ` Roland Dreier
2008-10-12 7:38 ` Grant Grundler
2008-10-12 7:20 ` Grant Grundler
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