From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sakari Ailus Subject: Re: [PATCH v2 2/3] omap3: change ISP's IOMMU da_start address Date: Wed, 09 Mar 2011 09:43:44 +0200 Message-ID: <4D772FB0.4020804@maxwell.research.nokia.com> References: <1299615316-17512-1-git-send-email-dacohen@gmail.com> <1299615316-17512-3-git-send-email-dacohen@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.nokia.com ([147.243.128.26]:18060 "EHLO mgw-da02.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751348Ab1CIHoR (ORCPT ); Wed, 9 Mar 2011 02:44:17 -0500 In-Reply-To: <1299615316-17512-3-git-send-email-dacohen@gmail.com> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: David Cohen Cc: Hiroshi.DOYU@nokia.com, linux-omap@vger.kernel.org, fernando.lugo@ti.com, linux-media@vger.kernel.org, laurent.pinchart@ideasonboard.com David Cohen wrote: > ISP doesn't consider 0x0 as a valid address, so it should explicitly > exclude first page from allowed 'da' range. > > Signed-off-by: David Cohen > --- > arch/arm/mach-omap2/omap-iommu.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/mach-omap2/omap-iommu.c b/arch/arm/mach-omap2/omap-iommu.c > index 3fc5dc7..3bea489 100644 > --- a/arch/arm/mach-omap2/omap-iommu.c > +++ b/arch/arm/mach-omap2/omap-iommu.c > @@ -33,7 +33,7 @@ static struct iommu_device omap3_devices[] = { > .name = "isp", > .nr_tlb_entries = 8, > .clk_name = "cam_ick", > - .da_start = 0x0, > + .da_start = 0x1000, > .da_end = 0xFFFFF000, > }, > }, Hi David! Thanks for the patch. My question is once again: is this necessary? My understanding is that the IOMMU allows mapping the NULL address if the user wishes to map it explicitly. da_end specifies the real hardware limit for the mapped top address, da_start should do the same for bottom. I think that the IOMMU users should be either able to rely that they get no NULL allocated automatically for them. Do we want or not want it to be part of the API? I don't think the ISP driver is a special case of all the possible drivers using the IOMMU. On the other hand, probably there will be an API change at some point for the IOMMU since as far as I remember, there are somewhat established APIs for IOMMUs in existence. Regards, -- Sakari Ailus sakari.ailus@maxwell.research.nokia.com