Re: [PATCH 2/2] iommu/arm-smmu: Allow client devices to select direct mapping

[Sai Prakash Ranjan]

Hi Robin,

On 2020-04-16 19:28, Robin Murphy wrote:
> On 2020-01-22 11:48 am, Sai Prakash Ranjan wrote:
> > From: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxxxxx>
> > Co-developed-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> > Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
> > ---
> >   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?

Sorry, I did not get the "grouping by the desired SMMU behaviour" thing.
Could you please give some more details?

> > +
> > +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.

Ok will use it.

> > +}
> > +
> > +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.

I'll wait till the dust settles down and then post the next version.

> >   	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...

Will move this out.

Thanks,
Sai

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