From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: Re: Tegra DRM device tree bindings Date: Thu, 28 Jun 2012 13:58:43 +0200 Message-ID: <20120628115843.GD15137@avionic-0098.mockup.avionic-design.de> 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: multipart/mixed; boundary="===============8983684205935869069==" Return-path: In-Reply-To: <4FEB4AC6.2060909-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Stephen Warren Cc: "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" List-Id: linux-tegra@vger.kernel.org --===============8983684205935869069== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="n2Pv11Ogg/Ox8ay5" Content-Disposition: inline --n2Pv11Ogg/Ox8ay5 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 27, 2012 at 12:02:46PM -0600, Stephen Warren wrote: > On 06/27/2012 06:44 AM, Hiroshi Doyu wrote: > ... > > I think that there are 2 cases: > >=20 > > (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=3D??M" in the kernel command line as below: > >=20 > > coherent_pool=3Dnn[KMG] [ARM,KNL] > > Sets the size of memory pool for coherent, atomic dma > > allocations. >=20 > I guess if that's the standard way of initializing CMA, then that's fine. >=20 > 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:-( Looking at Documentation/kernel-parameters.txt it seems the canonical way to initialize CMA is using the "cma" kernel command-line parameter. For device tree we could extend the "chosen" node to include something like "carveout =3D <0x04000000>;". Or "contiguous-memory" or whatever. Thierry --n2Pv11Ogg/Ox8ay5 Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iQIcBAEBAgAGBQJP7EbzAAoJEN0jrNd/PrOhhCEP/1PsDueyxAmE8VmpTvD2OJsf Q/4Db7Zq9PJi1qZDrfUzuVDCywgxZCRECsFsintsJUOT66u2YXJpfSCQbnoLP4B6 8VIVuvurj4018sf0kOKOoUblH8RRgM0Oi8BkxoB/BbLQDw/Qw9lq2xPwxR9ZbV5e 2tHuXv0/rx8rELP8XDJnsx5MWgY2wDL1Vp6fp58sOSOD3mypK5FrddeT6GlKBE9P SWJIeW9eOiqa9QDUXanioQeFluMY1PzpLGDCJ+FaDIQgH0QttJ+Z5MMsLaWQjrC5 xaPgWiRj8OWlXwSYbO2tryK0oOJ55V8Jk8iNnCFtSYTPYDIjN8xMUFDQko9fil0d Wy8edm/n9E7dlxCXwwEZrc/dH/7+TjuglDMwpF1KfNc3M0lrWAeggBHEON2bko62 JS+S59HRF7ZX8Q1hb1RYkDW95f6Uamtn6qyR+hU5Bn12N3Bu/PU06egCzz+/OPjQ rrwotUTl3C/l2l/Of3ApiQyYRktnbQfpWzq7w8kyaeaG4vdhggKiv5s+DHRlSgud YQkBLApykz1XAP6csHY/8RQyNlQsK9D1oAdaC/scjV2a8+b4QSpY/NjCzcy1+O6+ HANNTIHNxdWF9hQiH5BseC7qbXFRrcPgpEi4Y2fJmzj1l/BxefUbbHi+aGRoTPsO 45uVbSH+0K3FgNQKuJnj =wgnG -----END PGP SIGNATURE----- --n2Pv11Ogg/Ox8ay5-- --===============8983684205935869069== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ iommu mailing list iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org https://lists.linuxfoundation.org/mailman/listinfo/iommu --===============8983684205935869069==--