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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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