[PATCH v2 2/8] iommu/arm-smmu-v3: Use S2FWB when available

[Tian, Kevin]

> From: Jason Gunthorpe <jgg at nvidia.com>
> Sent: Tuesday, August 27, 2024 11:52 PM
> 
> @@ -4189,6 +4193,13 @@ static int arm_smmu_device_hw_probe(struct
> arm_smmu_device *smmu)
> 
>  	/* IDR3 */
>  	reg = readl_relaxed(smmu->base + ARM_SMMU_IDR3);
> +	/*
> +	 * If for some reason the HW does not support DMA coherency then
> using
> +	 * S2FWB won't work. This will also disable nesting support.
> +	 */
> +	if (FIELD_GET(IDR3_FWB, reg) &&
> +	    (smmu->features & ARM_SMMU_FEAT_COHERENCY))
> +		smmu->features |= ARM_SMMU_FEAT_S2FWB;
>  	if (FIELD_GET(IDR3_RIL, reg))
>  		smmu->features |= ARM_SMMU_FEAT_RANGE_INV;

then also clear ARM_SMMU_FEAT_NESTING?