[PATCH V2] iommu/arm-smmu-v2: Workaround for ThunderX errata#27704

[mark.rutland@arm.com (Mark Rutland)]

On Thu, Feb 18, 2016 at 10:29:18AM -0800, tchalamarla at caviumnetworks.com wrote:
> From: Tirumalesh Chalamarla <tchalamarla@caviumnetworks.com>
> 
> Due to Errata#27704 CN88xx SMMUv2,supports  only shared ASID and VMID
> namespaces; specifically within a given node SMMU0 and SMMU1 share,
> as does SMMU2 and SMMU3.
> 
> This patch tries to address these issuee by supplying asid and vmid
> base from devicetree.
> 
> changes from V1:
> 	- rebased on top of 16 bit VMID patch
> 	- removed redundent options from DT
> 	- insted of transform, DT now supplies starting ASID/VMID
> 
> Signed-off-by: Akula Geethasowjanya <Geethasowjanya.Akula@caviumnetworks.com>
> Signed-off-by: Tirumalesh Chalamarla <tchalamarla@caviumnetworks.com>
> ---
>  .../devicetree/bindings/iommu/arm,smmu.txt         |  8 +++++
>  drivers/iommu/arm-smmu.c                           | 37 +++++++++++++++-------
>  2 files changed, 34 insertions(+), 11 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.txt b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> index bb7e569..80b8484 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.txt
> @@ -57,6 +57,14 @@ conditions.
>  
>  - smmu-enable-vmid16 : Enable 16 bit VMID, if allowed.
>  
> +- asid-base :	Buggy SMMUv2 implementations which doesn't satisfy the
> +		ASID namespace needs, use this field to specify starting
> +		ASID for the SMMU.
> +
> +- vmid-base :	Buggy SMMUv2 implementations which doesn't satisfy the VMID
> +		namespace needs, use this field to specify starting VMID
> +		for the SMMU.

As has been pointed out, these are not strictly properties of the
hardware, and are insufficient to aovid the issue in general (adding an
arbitrary base does not enforce IDs fall within a particular range).

So NAK for *-base properties alone.

> +	if (of_property_read_u32(dev->of_node, "#asid-base",
> +				 &smmu->asid_base)) {
> +		smmu->asid_base = 0;
> +	}
> +
> +	if (of_property_read_u32(dev->of_node, "#vmid-base",
> +				 &smmu->vmid_base)) {
> +		smmu->vmid_base = 1;
> +	}

These do not match the documentation above.

Mark.