Re: [PATCH v3 8/9] iommu/arm-smmu: Support non-PCI devices with SMMUv3

[Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>]

On Tue, Jun 28, 2016 at 04:48:27PM +0100, Robin Murphy wrote:
> With the device <-> stream ID relationship suitably abstracted and
> of_xlate() hooked up, the PCI dependency now looks, and is, entirely
> arbitrary. Any bus using the of_dma_configure() mechanism will work,
> so extend support to the platform and AMBA buses which do just that.
> 
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
> ---
> 
> v3: Now actually tested; improve comment about duplicate IDs.
> 
>  drivers/iommu/Kconfig       |  2 +-
>  drivers/iommu/arm-smmu-v3.c | 42 ++++++++++++++++++++++++++++++++++--------
>  2 files changed, 35 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index ad0860383cb3..d1c66afefeed 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -308,7 +308,7 @@ config ARM_SMMU
>  
>  config ARM_SMMU_V3
>  	bool "ARM Ltd. System MMU Version 3 (SMMUv3) Support"
> -	depends on ARM64 && PCI
> +	depends on ARM64
>  	select IOMMU_API
>  	select IOMMU_IO_PGTABLE_LPAE
>  	select GENERIC_MSI_IRQ_DOMAIN
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 8ce2a4f9342b..735690e03818 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -35,6 +35,8 @@
>  #include <linux/pci.h>
>  #include <linux/platform_device.h>
>  
> +#include <linux/amba/bus.h>
> +
>  #include "io-pgtable.h"
>  
>  /* MMIO registers */
> @@ -1822,6 +1824,25 @@ static void arm_smmu_remove_device(struct device *dev)
>  	iommu_fwspec_free(dev);
>  }
>  
> +static struct iommu_group *arm_smmu_device_group(struct device *dev)
> +{
> +	struct iommu_group *group;
> +
> +	/*
> +	 * The difficulty of efficient stream-ID-to-device lookup prevents us
> +	 * from reasonably detecting aliasing outside of PCI buses, but for the
> +	 * the same underlying reason (a sparse 32-bit ID space) there's also

extra 'the'

> +	 * little excuse for systems to be wired up with non-unique IDs in the
> +	 * first place; consider them unsupported.
> +	 */

This is a long-winded way of saying "we don't support aliasing SIDs outside
of PCI".

Will