Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758868Ab2EURil (ORCPT ); Mon, 21 May 2012 13:38:41 -0400 Received: from ns.km20343-01.keymachine.de ([84.19.182.79]:41606 "EHLO km20343-01.keymachine.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1758415Ab2EURib (ORCPT ); Mon, 21 May 2012 13:38:31 -0400 Message-ID: <1337621908.1621.16.camel@tellur> Subject: Re: [PATCH 2/2] iommu/tegra: gart: Reserve iomem resource From: Lucas Stach To: Thierry Reding Cc: Stephen Warren , Hiroshi DOYU , linux-tegra@vger.kernel.org, Joerg Roedel , Bharat Nihalani , Vandana Salve , linux-kernel@vger.kernel.org Date: Mon, 21 May 2012 19:38:28 +0200 In-Reply-To: <20120521173124.GB11824@avionic-0098.mockup.avionic-design.de> References: <1337019127-6863-1-git-send-email-hdoyu@nvidia.com> <1337019127-6863-2-git-send-email-hdoyu@nvidia.com> <20120521141152.GA21513@avionic-0098.mockup.avionic-design.de> <4FBA702A.1010203@wwwdotorg.org> <1337619935.1621.13.camel@tellur> <4FBA77E2.4000409@wwwdotorg.org> <20120521173124.GB11824@avionic-0098.mockup.avionic-design.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.1 (3.4.1-2.fc17) Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2467 Lines: 51 Am Montag, den 21.05.2012, 19:31 +0200 schrieb Thierry Reding: > * Stephen Warren wrote: > > On 05/21/2012 11:05 AM, Lucas Stach wrote: > > > Am Montag, den 21.05.2012, 10:41 -0600 schrieb Stephen Warren: > > >> On 05/21/2012 08:11 AM, Thierry Reding wrote: > > >>> * Hiroshi DOYU wrote: > > >>>> GART Register/Aperture range should be reserved. > > >> ... > > >>>> diff --git a/drivers/iommu/tegra-gart.c > > >>>> b/drivers/iommu/tegra-gart.c > > >> ... > > >>>> + if (!devm_request_mem_region(dev, res_remap->start, + > > >>>> resource_size(res_remap), dev_name(dev))) { + dev_err(dev, > > >>>> "failed to reserve GART aperture\n"); + return -EBUSY; + } + > > >>> > > >>> I'm not so sure that this is a good idea. If the GART driver > > >>> requests the GART aperture, then users of the GART aperture (e.g. > > >>> the DRM driver) will no longer be able to use it. > > >> > > >> Presumably the DRM driver would be obtaining access to parts of the > > >> GART aperture through the GART driver, rather than just grabbing the > > >> IO region and using it for itself? > > > > > > With a TTM-like memory manager the DRM driver will take over the address > > > space management of the GART aperture. The GART driver is only used to > > > set up the mappings in the IOMMU. The DRM driver is the one that sets > > > up/tears down the CPU mappings on demand, so the aperture should be > > > claimed in the DRM driver. > > > > Even if the DRM driver is managing the aperture, I still think the GART > > driver should claim it. The physical address of the aperture is a > > property of the GART, so only the GART's resources (and DT node) should > > contain a representation of where that aperture is. The DRM driver > > should call into the GART driver to find out where the aperture is, and > > hence GART is able to claim it without conflict. > > That could be difficult to do. There isn't any API to allow this. I guess if > something like that is added it should probably go into the IOMMU framework. Ah, yes. There already was a plan to add properties for this to the IOMMU API. So I'm ok with the GART driver claiming the resources. I will try to push the needed API changes forward in the next few days. -- Lucas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/