Re: [RFC][PATCH 2/2] Add support of the IOMMU_DEVICE flag.

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

On Mon, Oct 06, 2014 at 11:28:16AM +0100, Varun Sethi wrote:
> This flag is used for specifying access to device memory. SMMU would apply
> device memory attributes for a DMA transaction. This is required for setting
> access to GIC registers, for generating message interrupts. This would ensure that 
> transactions targetting device memory are not gathered or reordered.
> 
> Signed-off-by: Varun Sethi <Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> ---
>  drivers/iommu/arm-smmu.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index ca18d6d..f8338d6 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1263,6 +1263,10 @@ static int arm_smmu_alloc_init_pte(struct arm_smmu_device *smmu, pmd_t *pmd,
>  		if (prot & IOMMU_CACHE)
>  			pteval |= (MAIR_ATTR_IDX_CACHE <<
>  				   ARM_SMMU_PTE_ATTRINDX_SHIFT);
> +
> +		if (prot & IOMMU_DEVICE)
> +			pteval |= (MAIR_ATTR_IDX_DEV <<
> +				   ARM_SMMU_PTE_ATTRINDX_SHIFT);

This is slightly odd, as I could in theory pass IOMMU_CACHE | IOMMU_DEVICE
to iommu_map.

Will