linux-kernel - Re: [PATCH 1/3] iommu/arm-smmu: Move to bitmap for arm_smmu

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Date:   Mon, 21 Jan 2019 13:51:47 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>, will.deacon@....com,
        joro@...tes.org, iommu@...ts.linux-foundation.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, tfiga@...omium.org,
        pratikp@...eaurora.org, pdaly@...eaurora.org,
        jcrouse@...eaurora.org
Subject: Re: [PATCH 1/3] iommu/arm-smmu: Move to bitmap for arm_smmu_domain
 atrributes

On 21/01/2019 05:53, Vivek Gautam wrote:
> A number of arm_smmu_domain's attributes can be assigned based
> on the iommu domains's attributes. These local attributes better
> be managed by a bitmap.
> So remove boolean flags and move to a 32-bit bitmap, and enable
> each bits separtely.
> 
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> ---
>   drivers/iommu/arm-smmu.c | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 7ebbcf1b2eb3..52b300dfc096 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -257,10 +257,11 @@ struct arm_smmu_domain {
>   	const struct iommu_gather_ops	*tlb_ops;
>   	struct arm_smmu_cfg		cfg;
>   	enum arm_smmu_domain_stage	stage;
> -	bool				non_strict;
>   	struct mutex			init_mutex; /* Protects smmu pointer */
>   	spinlock_t			cb_lock; /* Serialises ATS1* ops and TLB syncs */
>   	struct iommu_domain		domain;
> +#define ARM_SMMU_DOMAIN_ATTR_NON_STRICT	BIT(0)
> +	unsigned int			attr;
>   };
>   
>   struct arm_smmu_option_prop {
> @@ -901,7 +902,7 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
>   	if (smmu->features & ARM_SMMU_FEAT_COHERENT_WALK)
>   		pgtbl_cfg.quirks = IO_PGTABLE_QUIRK_NO_DMA;
>   
> -	if (smmu_domain->non_strict)
> +	if (smmu_domain->attr & ARM_SMMU_DOMAIN_ATTR_NON_STRICT)
>   		pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
>   
>   	/* Non coherent page table mappings only for Stage-1 */
> @@ -1598,7 +1599,8 @@ static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
>   	case IOMMU_DOMAIN_DMA:
>   		switch (attr) {
>   		case DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE:
> -			*(int *)data = smmu_domain->non_strict;
> +			*(int *)data = !!(smmu_domain->attr &
> +					  ARM_SMMU_DOMAIN_ATTR_NON_STRICT);
>   			return 0;
>   		default:
>   			return -ENODEV;
> @@ -1638,7 +1640,7 @@ static int arm_smmu_domain_set_attr(struct iommu_domain *domain,
>   	case IOMMU_DOMAIN_DMA:
>   		switch (attr) {
>   		case DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE:
> -			smmu_domain->non_strict = *(int *)data;
> +			smmu_domain->attr |= ARM_SMMU_DOMAIN_ATTR_NON_STRICT;

But what if *data == 0?

Robin.

>   			break;
>   		default:
>   			ret = -ENODEV;
>