linux-kernel - Re: [PATCHv2 2/6] iommu/arm-smmu: Allow client devices to select direct mapping

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Message-ID: <e35b10dc-8e58-f201-8485-9543dafbadfe@arm.com>
Date:   Mon, 20 Apr 2020 16:57:55 +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 2/6] iommu/arm-smmu: Allow client devices to select
 direct mapping

On 2020-04-20 3:37 pm, Sai Prakash Ranjan wrote:
> From: Jordan Crouse <jcrouse@...eaurora.org>
> 
> Some client devices want to directly map the IOMMU themselves instead
> of using the DMA domain. Allow those devices to opt in to direct
> mapping by way of a list of compatible strings.
> 
> Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
> Co-developed-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
> ---
>   drivers/iommu/arm-smmu-qcom.c | 19 +++++++++++++++++++
>   drivers/iommu/arm-smmu.h      |  1 +
>   2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
> index 64a4ab270ab7..0b3f159065aa 100644
> --- a/drivers/iommu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm-smmu-qcom.c
> @@ -3,6 +3,7 @@
>    * Copyright (c) 2019, The Linux Foundation. All rights reserved.
>    */
>   
> +#include <linux/of_device.h>
>   #include <linux/qcom_scm.h>
>   
>   #include "arm-smmu.h"
> @@ -11,6 +12,23 @@ struct qcom_smmu {
>   	struct arm_smmu_device smmu;
>   };
>   
> +static const struct of_device_id qcom_smmu_client_of_match[] = {
> +	{ .compatible = "qcom,adreno" },
> +	{ .compatible = "qcom,mdp4" },
> +	{ .compatible = "qcom,mdss" },
> +	{ .compatible = "qcom,sc7180-mdss" },
> +	{ .compatible = "qcom,sdm845-mdss" },
> +	{ }
> +};
> +
> +static int qcom_smmu_request_domain(struct device *dev)
> +{
> +	const struct of_device_id *match =
> +		of_match_device(qcom_smmu_client_of_match, dev);
> +
> +	return match ? IOMMU_DOMAIN_IDENTITY : 0;
> +}
> +
>   static int qcom_sdm845_smmu500_reset(struct arm_smmu_device *smmu)
>   {
>   	int ret;
> @@ -41,6 +59,7 @@ static int qcom_smmu500_reset(struct arm_smmu_device *smmu)
>   }
>   
>   static const struct arm_smmu_impl qcom_smmu_impl = {
> +	.req_domain = qcom_smmu_request_domain,
>   	.reset = qcom_smmu500_reset,
>   };
>   
> diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
> index 8d1cd54d82a6..662fdb4dccd2 100644
> --- a/drivers/iommu/arm-smmu.h
> +++ b/drivers/iommu/arm-smmu.h
> @@ -386,6 +386,7 @@ struct arm_smmu_impl {
>   	int (*init_context)(struct arm_smmu_domain *smmu_domain);
>   	void (*tlb_sync)(struct arm_smmu_device *smmu, int page, int sync,
>   			 int status);
> +	int (*req_domain)(struct device *dev);

Nit: since the point is to implement the full iommu_ops::def_domain_type 
interface, can we call it def_domain_type please?

Robin.

>   };
>   
>   static inline void __iomem *arm_smmu_page(struct arm_smmu_device *smmu, int n)
>