From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hiroshi Doyu Subject: Re: Tegra DRM device tree bindings Date: Thu, 28 Jun 2012 09:37:53 +0300 Message-ID: <20120628093753.545e0649fc84413837a5dca4@nvidia.com> References: <20120626105513.GA9552@avionic-0098.mockup.avionic-design.de> <20120626160224.40ba10a26e3dd3a56b1f312c@nvidia.com> <20120626140033.GC1115@avionic-0098.mockup.avionic-design.de> <20120627154400.d9d7db67128404079d98ab39@nvidia.com> <4FEB4AC6.2060909@wwwdotorg.org> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4FEB4AC6.2060909-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Stephen Warren Cc: Thierry Reding , "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: iommu@lists.linux-foundation.org On Wed, 27 Jun 2012 20:02:46 +0200 Stephen Warren wrote: > On 06/27/2012 06:44 AM, Hiroshi Doyu wrote: > ... > > I think that there are 2 cases: > > > > (1) discontiguous memory with IOMMU > > (2) contiguous memory without IOMMU(called "carveout" in general?) > ... > > For (2), although memory is mostly anonymous one, we may need to know > > how much to allocate, where we only need "size". This size is not from > > h/w feature, but it depends on the system load/usage. So I think that > > this size can be passed from kernel command line? For exmaple, we can > > specify how much contiguous memory is necessary with putting > > "coherent_pool=??M" in the kernel command line as below: > > > > coherent_pool=nn[KMG] [ARM,KNL] > > Sets the size of memory pool for coherent, atomic dma > > allocations. > > I guess if that's the standard way of initializing CMA, then that's fine. > > It'd be nice if there was a way to specify that from the DT too; that > way the user/distro/bootloader constructing the kernel command-line > wouldn't have to remember to add "random" (potentially > Tegra-/board-specific) extra arguments onto the command-line; the Tegra > command-line in the upstream kernel is quite clean right now, especially > compare to the enormous number of options we require downstream:-( DT can specify the kernel command-line as "bootargs" in a dts file, which can be modified after extracted on memory by bootloader.