From mboxrd@z Thu Jan  1 00:00:00 1970
From: arnd@arndb.de (Arnd Bergmann)
Date: Tue, 4 Feb 2014 17:01:59 +0100
Subject: [RFC/RFT 2/2] ARM: keystone: Install hooks for dma address
 translation routines
In-Reply-To: <52F0F979.2090505@ti.com>
References: <1391470107-15927-1-git-send-email-santosh.shilimkar@ti.com>
 <CAOesGMgzsx3gE6cT-nMTJfnO1T5pvfTr8HA6tVGv8svF_kCYjg@mail.gmail.com>
 <52F0F979.2090505@ti.com>
Message-ID: <201402041702.00039.arnd@arndb.de>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tuesday 04 February 2014, Santosh Shilimkar wrote:
> > PPC servers use "ibm,dma-window" to describe the assigned dma address
> > space for busses/devices, but the window itself doesn't contain any
> > information about the physical address mapping (since it goes through
> > an iommu after that). It likely doesn't fit this particular use case,
> > but it's something we should look at as a base in case we need to
> > start looking at bindings for this instead of coding it per SoC. We'll
> > know more once we've seen what a few of the implementations out there
> > are.
> > 
> Understood.

I think you are looking for the "dma-ranges" property, which describes
how a device DMA address space maps into the parent bus address space
for inbound translations. It's not used much in Linux, but it is clearly
specified. The "ibm,dma-window" property OTOH is for the corner case
that you have a small per-partition DMA address space section, which is
not how things are done on most systems these days.

	Arnd