From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH 1/1] arm/dts: Tegra30: Add device tree support for SMMU Date: Wed, 18 Apr 2012 11:31:12 -0600 Message-ID: <4F8EFA60.2040400@wwwdotorg.org> References: <20120413.132205.1766846402066131036.hdoyu@nvidia.com> <4F887F9B.700@wwwdotorg.org> <20120416.131059.331282986467061278.hdoyu@nvidia.com> <4F8C43AA.7090107@wwwdotorg.org> <20120418081017.d3c630c6f7d09cd4ed039854@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120418081017.d3c630c6f7d09cd4ed039854-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Hiroshi Doyu Cc: "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" List-Id: devicetree@vger.kernel.org On 04/17/2012 11:10 PM, Hiroshi Doyu wrote: > On Mon, 16 Apr 2012 18:07:06 +0200 > Stephen Warren wrote: > >> On 04/16/2012 04:10 AM, Hiroshi Doyu wrote: >>> Stephen Warren wrote at Fri, 13 Apr 2012 21:33:47 +0200: >>>> On 04/13/2012 04:22 AM, Hiroshi Doyu wrote: >>>>> Add device tree support for Tegra30 IOMMU(SMMU). >> ... >>>> But why does the SMMU driver expect to control the AHB arbitration >>>> registers? They seem unrelated to the SMMU. >>> >>> It's necessary to inform AHB that SMMU is ready to use. There's a >>> dedicated bit for SMMU in this AHB arbitration register. >> >> Shouldn't there be a dedicated driver for the AHB arbitration registers >> that the SMMU driver calls into to achieve this? IIRC, the AHB >> arbitration registers support much more than the SMMU enable, and if we >> ever need to touch those other features, going to the SMMU driver to do >> so probably wouldn't make sense. > > Agree. Sounds like the way to go. > > We haven't upstreamed AHB driver yet. So is it ok to remove AHB entry > from SMMU dt and add AHB function call when upstreaming AHB driver? > I'll work on that. I think that seems reasonable for now, yes. I assume you mean implementing e.g. arch/arm/mach-tegra/tegra30-ahb.c, similar to how, say, the fuse APIs work.