linux-kernel - Re: [PATCH 2/7 v2] powerpc/dma-mapping: override dma_get_page

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Date:	Wed, 28 Oct 2015 12:20:58 +0900
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Nishanth Aravamudan <nacc@...ux.vnet.ibm.com>
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	Michael Ellerman <mpe@...erman.id.au>,
	Matthew Wilcox <willy@...ux.intel.com>,
	Keith Busch <keith.busch@...el.com>,
	Paul Mackerras <paulus@...ba.org>,
	David Gibson <david@...son.dropbear.id.au>,
	Christoph Hellwig <hch@...radead.org>,
	"David S. Miller" <davem@...emloft.net>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org
Subject: Re: [PATCH 2/7 v2] powerpc/dma-mapping: override dma_get_page_shift

On Tue, 2015-10-27 at 19:30 -0700, Nishanth Aravamudan wrote:
> On 28.10.2015 [11:20:05 +0900], Benjamin Herrenschmidt wrote:
> > On Tue, 2015-10-27 at 18:54 -0700, Nishanth Aravamudan wrote:
> > > 
> > > In "bypass" mode, what TCE size is used? Is it guaranteed to be
> > > 4K?
> > 
> > None :-) The TCEs are completely bypassed. You get a N:M linear
> > mapping
> > of all memory starting at 1<<59 PCI side.
> 
> Err, duh, sorry! Ok, so in that case, DMA page shift is PAGE_SHIFT,
> then?

I think so.

Cheers,
Ben.


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