From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: Tegra DRM device tree bindings Date: Tue, 26 Jun 2012 20:48:18 -0600 Message-ID: <4FEA7472.7050201@nvidia.com> References: <20120626105513.GA9552@avionic-0098.mockup.avionic-design.de> <20120626160224.40ba10a26e3dd3a56b1f312c@nvidia.com> <20120626140033.GC1115@avionic-0098.mockup.avionic-design.de> <23B010BBA481A74B98487467C29BA57BF2361DA3AA@HKMAIL01.nvidia.com> <4FEA6E09.30800@nvidia.com> <23B010BBA481A74B98487467C29BA57BF2361DA3C4@HKMAIL01.nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <23B010BBA481A74B98487467C29BA57BF2361DA3C4-Q4EWCATADntDw2glCA4ptUEOCMrvLtNR@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Mark Zhang Cc: Thierry Reding , Hiroshi Doyu , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Lucas Stach List-Id: devicetree@vger.kernel.org On 06/26/2012 08:32 PM, Mark Zhang wrote: >> On 06/26/2012 07:46 PM, Mark Zhang wrote: >>>>> On Tue, 26 Jun 2012 12:55:13 +0200 >>>>> Thierry Reding wrote: >> ... >>>> I'm not sure I understand how information about the carveout would be >>>> obtained from the IOMMU API, though. >>> >>> I think that can be similar with current gart implementation. Define carveout as: >>> >>> carveout { >>> compatible = "nvidia,tegra20-carveout"; >>> size = <0x10000000>; >>> }; >>> >>> Then create a file such like "tegra-carveout.c" to get these definitions and >> register itself as platform device's iommu instance. >> >> The carveout isn't a HW object, so it doesn't seem appropriate to define a DT >> node to represent it. > > Yes. But I think it's better to export the size of carveout as a configurable item. > So we need to define this somewhere. How about define carveout as a property of gart? There already exists a way of preventing Linux from using certain chunks of memory; the /memreserve/ syntax. From a brief look at the dtc source, it looks like /memreserve/ entries can have labels, which implies that a property in the GART node could refer to the /memreserve/ entry by phandle in order to know what memory regions to use.