Hi Thierry,

Thank you for the patch.

On Wednesday 04 February 2015 08:58:08 Thierry Reding wrote:
> From: Thierry Reding <[email protected]>
> 
> 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 <[email protected]>
> Cc: Tony Lindgren <[email protected]>
> Cc: Suman Anna <[email protected]>
> Cc: Laurent Pinchart <[email protected]>
> Signed-off-by: Thierry Reding <[email protected]>
> ---
>  drivers/iommu/omap-iommu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iommu/omap-iommu.c b/drivers/iommu/omap-iommu.c
> index bbb7dcef02d3..e4d4f133a3b3 100644
> --- a/drivers/iommu/omap-iommu.c
> +++ b/drivers/iommu/omap-iommu.c
> @@ -1377,6 +1377,9 @@ static int __init omap_iommu_init(void)
>       const unsigned long flags = SLAB_HWCACHE_ALIGN;
>       size_t align = 1 << 10; /* L2 pagetable alignement */
> 
> +     if (!of_find_matching_node(NULL, omap_iommu_of_match))
> +             return 0;
> +

We should convert the omap-iommu driver to proper DT instantiation, but this 
should do for now.

>       p = kmem_cache_create("iopte_cache", IOPTE_TABLE_SIZE, align, flags,
>                             iopte_cachep_ctor);
>       if (!p)
> @@ -1394,6 +1397,9 @@ subsys_initcall(omap_iommu_init);
> 
>  static void __exit omap_iommu_exit(void)
>  {
> +     if (!of_find_matching_node(NULL, omap_iommu_of_match))
> +             return;
> +
>       kmem_cache_destroy(iopte_cachep);
> 
>       platform_driver_unregister(&omap_iommu_driver);

The exit function will never be called as the omap-iommu driver is always 
built-in. You could just remove the exit function.

-- 
Regards,

Laurent Pinchart

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