iommu/omap: Play nice in multi-platform builds

The OMAP IOMMU driver unconditionally executes code and registers a
struct iommu_ops with the platform bus irrespective of whether it runs
on an OMAP 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
OMAP IOMMU 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 OMAP IOMMU.

Reported-by: Nicolas Chauvet <kwizart@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Suman Anna <s-anna@ti.com>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
index f59f857b702e8e3f65080edd43b743a54091170f..a4ba851825c235b5bfa7ab93a8256adfca160ca7 100644 (file)
--- a/drivers/iommu/omap-iommu.c
+++ b/drivers/iommu/omap-iommu.c
@@ -1376,6 +1376,13 @@ static int __init omap_iommu_init(void)
        struct kmem_cache *p;
        const unsigned long flags = SLAB_HWCACHE_ALIGN;
        size_t align = 1 << 10; /* L2 pagetable alignement */
+       struct device_node *np;
+
+       np = of_find_matching_node(NULL, omap_iommu_of_match);
+       if (!np)
+               return 0;
+
+       of_node_put(np);
 
        p = kmem_cache_create("iopte_cache", IOPTE_TABLE_SIZE, align, flags,
                              iopte_cachep_ctor);