[RFC PATCH] iommu/arm-smmu: Add global SMR masking property

[Nipun Gupta]

> -----Original Message-----
> From: iommu-bounces at lists.linux-foundation.org [mailto:iommu-
> bounces at lists.linux-foundation.org] On Behalf Of Robin Murphy
> Sent: Friday, December 16, 2016 18:49
> To: iommu at lists.linux-foundation.org; devicetree at vger.kernel.org; linux-arm-
> kernel at lists.infradead.org
> Cc: mark.rutland at arm.com; will.deacon at arm.com; Stuart Yoder
> <stuart.yoder at nxp.com>
> Subject: [RFC PATCH] iommu/arm-smmu: Add global SMR masking property
> 
> The current SMR masking support using a 2-cell iommu-specifier is
> primarily intended to handle individual masters with large and/or
> complex Stream ID assignments; it quickly gets a bit clunky in other SMR
> use-cases where we just want to consistently mask out the same part of
> every Stream ID (e.g. for MMU-500 configurations where the appended TBU
> number gets in the way unnecessarily). Let's add a new property to allow
> a single global mask value to better fit the latter situation.
> 
> CC: Stuart Yoder <stuart.yoder at nxp.com>

Tested-by: Nipun Gupta <nipun.gupta at nxp.com>

> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---
> 
> Compile-tested only...
> 
>  Documentation/devicetree/bindings/iommu/arm,smmu.txt | 8 ++++++++
>  drivers/iommu/arm-smmu.c                             | 4 +++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> index e862d1485205..98f5cbe5fdb4 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> @@ -60,6 +60,14 @@ conditions.
>                    aliases of secure registers have to be used during
>                    SMMU configuration.
> 
> +- stream-match-mask : Specifies a fixed SMR mask value to combine with
> +                  the Stream ID value from every iommu-specifier. This
> +                  may be used instead of an "#iommu-cells" value of 2
> +                  when there is no need for per-master SMR masks, but
> +                  it is still desired to mask some portion of every
> +                  Stream ID (e.g. for certain MMU-500 configurations
> +                  given globally unique external IDs).
> +
>  ** Deprecated properties:
> 
>  - mmu-masters (deprecated in favour of the generic "iommus" binding) :
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 8f7281444551..f1abcb7dde36 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1534,13 +1534,15 @@ static int arm_smmu_domain_set_attr(struct
> iommu_domain *domain,
> 
>  static int arm_smmu_of_xlate(struct device *dev, struct of_phandle_args *args)
>  {
> -	u32 fwid = 0;
> +	u32 mask, fwid = 0;
> 
>  	if (args->args_count > 0)
>  		fwid |= (u16)args->args[0];
> 
>  	if (args->args_count > 1)
>  		fwid |= (u16)args->args[1] << SMR_MASK_SHIFT;
> +	else if (!of_property_read_u32(args->np, "stream-match-mask",
> &mask))
> +		fwid |= (u16)mask << SMR_MASK_SHIFT;
> 
>  	return iommu_fwspec_add_ids(dev, &fwid, 1);
>  }
> --
> 2.10.2.dirty
> 
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