linux-kernel - Re: [PATCHv2 3/6] iommu/arm-smmu: Implement iommu_ops->def_domain

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Date:   Mon, 20 Apr 2020 16:26:22 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Will Deacon <will@...nel.org>, Joerg Roedel <joro@...tes.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Rob Clark <robdclark@...il.com>
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Evan Green <evgreen@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        iommu@...ts.linux-foundation.org,
        Matthias Kaehlcke <mka@...omium.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv2 3/6] iommu/arm-smmu: Implement
 iommu_ops->def_domain_type call-back

On 2020-04-20 3:37 pm, Sai Prakash Ranjan wrote:
> Implement the new def_domain_type call-back for the ARM
> SMMU driver. We need this to support requesting the domain
> type by the client devices.
> 
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> ---
>   drivers/iommu/arm-smmu.c | 20 ++++++++++++++++++++
>   1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index e622f4e33379..b5d1d52dfbb8 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1609,6 +1609,25 @@ static void arm_smmu_get_resv_regions(struct device *dev,
>   	iommu_dma_get_resv_regions(dev, head);
>   }
>   
> +static int arm_smmu_def_domain_type(struct device *dev)
> +{
> +	struct iommu_fwspec *fwspec;
> +	struct arm_smmu_device *smmu;
> +
> +	fwspec = dev_iommu_fwspec_get(dev);
> +	if (!fwspec || fwspec->ops != &arm_smmu_ops)
> +		return -ENODEV;
> +
> +	smmu = arm_smmu_get_by_fwnode(fwspec->iommu_fwnode);
> +	if (!smmu)
> +		return -ENODEV;
> +

AFAICS this should only ever be called for a device in a group, which 
means an initial ->probe_device has succeeded and rather than 
defensively going the long way round, we can safely assume this:

	struct arm_smmu_master_cfg = dev_iommu_priv_get(dev);
	struct arm_smmu_impl *impl = cfg->smmu->impl;

	if (impl && impl->req_domain)
		return impl->req_domain(dev);

Or have I misunderstood the flow?

Robin.

> +	if (smmu->impl && smmu->impl->req_domain)
> +		return smmu->impl->req_domain(dev);
> +
> +	return 0;
> +}
> +
>   static struct iommu_ops arm_smmu_ops = {
>   	.capable		= arm_smmu_capable,
>   	.domain_alloc		= arm_smmu_domain_alloc,
> @@ -1627,6 +1646,7 @@ static struct iommu_ops arm_smmu_ops = {
>   	.of_xlate		= arm_smmu_of_xlate,
>   	.get_resv_regions	= arm_smmu_get_resv_regions,
>   	.put_resv_regions	= generic_iommu_put_resv_regions,
> +	.def_domain_type	= arm_smmu_def_domain_type,
>   	.pgsize_bitmap		= -1UL, /* Restricted during device attach */
>   };
>   
>