From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Szyprowski Subject: Re: [PATCH 1/4] iommu/exynos: Play nice in multi-platform builds Date: Wed, 04 Feb 2015 12:26:40 +0100 Message-ID: <54D201F0.9090105@samsung.com> References: <1423036690-3862-1-git-send-email-thierry.reding@gmail.com> <1423036690-3862-2-git-send-email-thierry.reding@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-reply-to: <1423036690-3862-2-git-send-email-thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@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: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hello, On 2015-02-04 08:58, Thierry Reding wrote: > From: Thierry Reding > > The Exynos System MMU driver unconditionally executes code and registers > a struct iommu_ops with the platform bus irrespective of whether it runs > on an Exynos SoC or not. This causes problems in multi-platform kernels > where drivers for other SoCs will no longer be able to register their > own struct iommu_ops or even try to use a struct iommu_ops for an IOMMU > that obviously isn't there. > > The smallest fix I could think of is to check for the existence of any > Exynos System MMU devices in the device tree and skip initialization > otherwise. > > This fixes a problem on Tegra20 where the DRM driver will try to use the > obviously non-existent Exynos System MMU. > > Reported-by: Nicolas Chauvet > Cc: Kukjin Kim > Signed-off-by: Thierry Reding Frankly, you may mark the existing exynos iommu driver as BROKEN, what will solve a few other issues as well. In the current version this driver is not functional and not used on any platform. I thought that my fixes will get into v3.20, but it looks that it won't happen. > --- > drivers/iommu/exynos-iommu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/iommu/exynos-iommu.c b/drivers/iommu/exynos-iommu.c > index 7ce52737c7a1..d4b41fa32368 100644 > --- a/drivers/iommu/exynos-iommu.c > +++ b/drivers/iommu/exynos-iommu.c > @@ -1188,6 +1188,9 @@ static int __init exynos_iommu_init(void) > { > int ret; > > + if (!of_find_matching_node(NULL, sysmmu_of_match)) > + return 0; > + > lv2table_kmem_cache = kmem_cache_create("exynos-iommu-lv2table", > LV2TABLE_SIZE, LV2TABLE_SIZE, 0, NULL); > if (!lv2table_kmem_cache) { Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland