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SubjectRe: [PATCH 2/2] iommu/arm-smmu: Allow client devices to select direct mapping
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On 2020-01-22 11:48 am, Sai Prakash Ranjan wrote:
> From: Jordan Crouse <jcrouse@codeaurora.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@codeaurora.org>
> Co-developed-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> ---
> drivers/iommu/arm-smmu-qcom.c | 39 +++++++++++++++++++++++++++++++++++
> drivers/iommu/arm-smmu.c | 3 +++
> drivers/iommu/arm-smmu.h | 5 +++++
> 3 files changed, 47 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
> index 64a4ab270ab7..ff746acd1c81 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 +12,43 @@ struct qcom_smmu {
> struct arm_smmu_device smmu;
> };
>
> +static const struct arm_smmu_client_match_data qcom_adreno = {
> + .direct_mapping = true,
> +};
> +
> +static const struct arm_smmu_client_match_data qcom_mdss = {
> + .direct_mapping = true,
> +};

Might it make sense to group these by the desired SMMU behaviour rather
than (apparently) what kind of device the client happens to be, which
seems like a completely arbitrary distinction from the SMMU driver's PoV?

> +
> +static const struct of_device_id qcom_smmu_client_of_match[] = {
> + { .compatible = "qcom,adreno", .data = &qcom_adreno },
> + { .compatible = "qcom,mdp4", .data = &qcom_mdss },
> + { .compatible = "qcom,mdss", .data = &qcom_mdss },
> + { .compatible = "qcom,sc7180-mdss", .data = &qcom_mdss },
> + { .compatible = "qcom,sdm845-mdss", .data = &qcom_mdss },
> + {},
> +};
> +
> +static const struct arm_smmu_client_match_data *
> +qcom_smmu_client_data(struct device *dev)
> +{
> + const struct of_device_id *match =
> + of_match_device(qcom_smmu_client_of_match, dev);
> +
> + return match ? match->data : NULL;

of_device_get_match_data() is your friend.

> +}
> +
> +static int qcom_smmu_request_domain(struct device *dev)
> +{
> + const struct arm_smmu_client_match_data *client;
> +
> + client = qcom_smmu_client_data(dev);
> + if (client)
> + iommu_request_dm_for_dev(dev);
> +
> + return 0;
> +}
> +
> static int qcom_sdm845_smmu500_reset(struct arm_smmu_device *smmu)
> {
> int ret;
> @@ -41,6 +79,7 @@ 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.c b/drivers/iommu/arm-smmu.c
> index 16c4b87af42b..67dd9326247a 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1448,6 +1448,9 @@ static int arm_smmu_add_device(struct device *dev)
> device_link_add(dev, smmu->dev,
> DL_FLAG_PM_RUNTIME | DL_FLAG_AUTOREMOVE_SUPPLIER);
>
> + if (smmu->impl && smmu->impl->req_domain)
> + return smmu->impl->req_domain(dev);
> +

There are about 5 different patchsets flying around at the moment that
all touch default domain allocation, so this is a fast-moving target,
but I think where the dust should settle is with arm_smmu_ops forwarding
.def_domain_type (or whatever it ends up as) calls to arm_smmu_impl as
appropriate.

> return 0;
>
> out_cfg_free:
> diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
> index 8d1cd54d82a6..059dc9c39f64 100644
> --- a/drivers/iommu/arm-smmu.h
> +++ b/drivers/iommu/arm-smmu.h
> @@ -244,6 +244,10 @@ enum arm_smmu_arch_version {
> ARM_SMMU_V2,
> };
>
> +struct arm_smmu_client_match_data {
> + bool direct_mapping;
> +};

Does this need to be public? I don't see the other users...

Robin.

> +
> enum arm_smmu_implementation {
> GENERIC_SMMU,
> ARM_MMU500,
> @@ -386,6 +390,7 @@ 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);
> };
>
> static inline void __iomem *arm_smmu_page(struct arm_smmu_device *smmu, int n)
>

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