On Tue, Mar 07, 2017 at 06:26:28PM +0000, Robin Murphy wrote:
> 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.
>
> Tested-by: Nipun Gupta <nipun.gupta@xxxxxxx>
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> ---
>
> Time to rekindle the discussion about whether an architecture-level
> concept with a rather specific name needs a vendor prefix ;)
>
> Robin.
>
> Documentation/devicetree/bindings/iommu/arm,smmu.txt | 10 ++++++++++
> drivers/iommu/arm-smmu.c | 4 +++-
> 2 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> index 6cdf32d037fc..d66f355e174f 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> @@ -60,6 +60,16 @@ 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). This property is
> + not valid for SMMUs using stream indexing, and may be
> + ignored if stream matching is not supported.
> +
Generally, this sounds fine.
However, there is an ambiguity here (inherited from the existing
#iommu-cells = <2> case), in that it's not clear what is meant by "to
combine".
>From the example at the end of the file, this appears to be a mask of
bits to not consider for matching purposes?
Would you mind clarifying that in both cases?
This could also do with an example.
Thanks,
Mark.
> ** 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 abf6496843a6..e394d55146a6 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1590,13 +1590,15 @@ 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);
> }
> --
> 2.11.0.dirty
>
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