From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 29 Jan 2008 09:50:48 -0600 From: Olof Johansson To: Michael Ellerman Subject: Re: [PATCH 8/8] Cell IOMMU fixed mapping support Message-ID: <20080129155048.GA19822@lixom.net> References: <56662c291890f09835ef7251f9b86f70fbee3ad2.1201616038.git.michael@ellerman.id.au> <1cbc0deea968ece13756e3c86ec3af0b7586b80b.1201616038.git.michael@ellerman.id.au> <20080129151511.GA18975@lixom.net> <1201619625.10012.19.camel@concordia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1201619625.10012.19.camel@concordia> Cc: linuxppc-dev@ozlabs.org, cbe-oss-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Jan 30, 2008 at 02:13:45AM +1100, Michael Ellerman wrote: > On Tue, 2008-01-29 at 09:15 -0600, Olof Johansson wrote: > > On Wed, Jan 30, 2008 at 01:14:03AM +1100, Michael Ellerman wrote: > > > > > For example a machine with 4GB of memory would end up with the normal > > > IOMMU window from 0-2GB and the fixed mapping window from 2GB to 6GB. In > > > this case a 64-bit device wishing to DMA to 1GB would be told to DMA to > > > 3GB, plus any offset required by firmware. The firmware offset is encoded > > > in the "dma-ranges" property. > > > > Shouldn't the fixed mapping be between 4G and 8G (and the offset for 1G > > is at 5G), to account for the MMIO range at 2-4G? > > I don't think so, ie. it works setup like that, but I'm not entirely > sure why. Presumably the 2-4GB for MMIO is only for cycles heading out > of the CPU. Ben denied that being so yesterday. :-) If that's the case, then you can stick the dynamic range there for >32GB configs, since it's still addressable with 32 bits. -Olof