From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx192.postini.com [74.125.245.192]) by kanga.kvack.org (Postfix) with SMTP id E5BE06B002B for ; Tue, 16 Oct 2012 10:13:43 -0400 (EDT) From: Hiroshi Doyu Date: Tue, 16 Oct 2012 16:13:38 +0200 Subject: Re: [Linaro-mm-sig] [RFC 0/2] DMA-mapping & IOMMU - physically contiguous allocations Message-ID: <20121016.171338.1300372057637804407.hdoyu@nvidia.com> References: <20121016090434.7d5e088152a3e0b0606903c8@nvidia.com> In-Reply-To: Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: "inki.dae@samsung.com" Cc: "m.szyprowski@samsung.com" , "linux@arm.linux.org.uk" , "arnd@arndb.de" , "linux-kernel@vger.kernel.org" , "linaro-mm-sig@lists.linaro.org" , "linux-mm@kvack.org" , "kyungmin.park@samsung.com" , "linux-arm-kernel@lists.infradead.org" , "linux-tegra@vger.kernel.org" Hi Inki, Inki Dae wrote @ Tue, 16 Oct 2012 12:12:49 +0200: > Hi Hiroshi, >=20 > 2012/10/16 Hiroshi Doyu : > > Hi Inki/Marek, > > > > On Tue, 16 Oct 2012 02:50:16 +0200 > > Inki Dae wrote: > > > >> 2012/10/15 Marek Szyprowski : > >> > Hello, > >> > > >> > Some devices, which have IOMMU, for some use cases might require to > >> > allocate a buffers for DMA which is contiguous in physical memory. S= uch > >> > use cases appears for example in DRM subsystem when one wants to imp= rove > >> > performance or use secure buffer protection. > >> > > >> > I would like to ask if adding a new attribute, as proposed in this R= FC > >> > is a good idea? I feel that it might be an attribute just for a sing= le > >> > driver, but I would like to know your opinion. Should we look for ot= her > >> > solution? > >> > > >> > >> In addition, currently we have worked dma-mapping-based iommu support > >> for exynos drm driver with this patch set so this patch set has been > >> tested with iommu enabled exynos drm driver and worked fine. actually, > >> this feature is needed for secure mode such as TrustZone. in case of > >> Exynos SoC, memory region for secure mode should be physically > >> contiguous and also maybe OMAP but now dma-mapping framework doesn't > >> guarantee physically continuous memory allocation so this patch set > >> would make it possible. > > > > Agree that the contigous memory allocation is necessary for us too. > > > > In addition to those contiguous/discontiguous page allocation, is > > there any way to _import_ anonymous pages allocated by a process to be > > used in dma-mapping API later? > > > > I'm considering the following scenario, an user process allocates a > > buffer by malloc() in advance, and then it asks some driver to convert > > that buffer into IOMMU'able/DMA'able ones later. In this case, pages > > are discouguous and even they may not be yet allocated at > > malloc()/mmap(). > > >=20 > I'm not sure I understand what you mean but we had already tried this > way and for this, you can refer to below link, > http://www.mail-archive.com/dri-devel@lists.freedesktop.or= g/msg22555.html The above patch doesn't seem to have so much platform/SoC specific code but rather it could common over other SoC as well. Is there any plan to make it more generic, which can be used by other DRM drivers? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org