Re: [RFC PATCH 01/11] iommu/arm-smmu-v3: Add feature detection for HTTU

[Robin Murphy]

On 2021-01-28 15:17, Keqian Zhu wrote:
> From: jiangkunkun <jiangkunkun@xxxxxxxxxx>
>
> The SMMU which supports HTTU (Hardware Translation Table Update) can
> update the access flag and the dirty state of TTD by hardware. It is
> essential to track dirty pages of DMA.
>
> This adds feature detection, none functional change.
>
> Co-developed-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx>
> Signed-off-by: Kunkun Jiang <jiangkunkun@xxxxxxxxxx>
> ---
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++++
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  8 ++++++++
>   include/linux/io-pgtable.h                  |  1 +
>   3 files changed, 25 insertions(+)
>
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 8ca7415d785d..0f0fe71cc10d 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -1987,6 +1987,7 @@ static int arm_smmu_domain_finalise(struct iommu_domain *domain,
>   		.pgsize_bitmap	= smmu->pgsize_bitmap,
>   		.ias		= ias,
>   		.oas		= oas,
> +		.httu_hd	= smmu->features & ARM_SMMU_FEAT_HTTU_HD,
>   		.coherent_walk	= smmu->features & ARM_SMMU_FEAT_COHERENCY,
>   		.tlb		= &arm_smmu_flush_ops,
>   		.iommu_dev	= smmu->dev,
> @@ -3224,6 +3225,21 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
>   	if (reg & IDR0_HYP)
>   		smmu->features |= ARM_SMMU_FEAT_HYP;
>   
> +	switch (FIELD_GET(IDR0_HTTU, reg)) {

We need to accommodate the firmware override as well if we need this to 
be meaningful. Jean-Philippe is already carrying a suitable patch in the 
SVA stack[1].

> +	case IDR0_HTTU_NONE:
> +		break;
> +	case IDR0_HTTU_HA:
> +		smmu->features |= ARM_SMMU_FEAT_HTTU_HA;
> +		break;
> +	case IDR0_HTTU_HAD:
> +		smmu->features |= ARM_SMMU_FEAT_HTTU_HA;
> +		smmu->features |= ARM_SMMU_FEAT_HTTU_HD;
> +		break;
> +	default:
> +		dev_err(smmu->dev, "unknown/unsupported HTTU!\n");
> +		return -ENXIO;
> +	}
> +
>   	/*
>   	 * The coherency feature as set by FW is used in preference to the ID
>   	 * register, but warn on mismatch.
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> index 96c2e9565e00..e91bea44519e 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
> @@ -33,6 +33,10 @@
>   #define IDR0_ASID16			(1 << 12)
>   #define IDR0_ATS			(1 << 10)
>   #define IDR0_HYP			(1 << 9)
> +#define IDR0_HTTU			GENMASK(7, 6)
> +#define IDR0_HTTU_NONE			0
> +#define IDR0_HTTU_HA			1
> +#define IDR0_HTTU_HAD			2
>   #define IDR0_COHACC			(1 << 4)
>   #define IDR0_TTF			GENMASK(3, 2)
>   #define IDR0_TTF_AARCH64		2
> @@ -286,6 +290,8 @@
>   #define CTXDESC_CD_0_TCR_TBI0		(1ULL << 38)
>   
>   #define CTXDESC_CD_0_AA64		(1UL << 41)
> +#define CTXDESC_CD_0_HD			(1UL << 42)
> +#define CTXDESC_CD_0_HA			(1UL << 43)
>   #define CTXDESC_CD_0_S			(1UL << 44)
>   #define CTXDESC_CD_0_R			(1UL << 45)
>   #define CTXDESC_CD_0_A			(1UL << 46)
> @@ -604,6 +610,8 @@ struct arm_smmu_device {
>   #define ARM_SMMU_FEAT_RANGE_INV		(1 << 15)
>   #define ARM_SMMU_FEAT_BTM		(1 << 16)
>   #define ARM_SMMU_FEAT_SVA		(1 << 17)
> +#define ARM_SMMU_FEAT_HTTU_HA		(1 << 18)
> +#define ARM_SMMU_FEAT_HTTU_HD		(1 << 19)
>   	u32				features;
>   
>   #define ARM_SMMU_OPT_SKIP_PREFETCH	(1 << 0)
> diff --git a/include/linux/io-pgtable.h b/include/linux/io-pgtable.h
> index ea727eb1a1a9..1a00ea8562c7 100644
> --- a/include/linux/io-pgtable.h
> +++ b/include/linux/io-pgtable.h
> @@ -97,6 +97,7 @@ struct io_pgtable_cfg {
>   	unsigned long			pgsize_bitmap;
>   	unsigned int			ias;
>   	unsigned int			oas;
> +	bool				httu_hd;

This is very specific to the AArch64 stage 1 format, not a generic 
capability - I think it should be a quirk flag rather than a common field.

Robin.

[1] 
https://jpbrucker.net/git/linux/commit/?h=sva/current&id=1ef7d512fb9082450dfe0d22ca4f7e35625a097b

>   	bool				coherent_walk;
>   	const struct iommu_flush_ops	*tlb;
>   	struct device			*iommu_dev;