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

[Sai Prakash Ranjan]

Hi Evan,

On 2020-04-14 04:42, Evan Green wrote:
> On Wed, Jan 22, 2020 at 3:48 AM Sai Prakash Ranjan
> <saiprakash.ranjan@xxxxxxxxxxxxxx> 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,
>
> I don't actually see direct_mapping being used. Shouldn't this member
> be checked somewhere?

Thanks for spotting this, my bad. It should be checked in 
qcom_smmu_request_domain().

diff --git a/drivers/iommu/arm-smmu-qcom.c 
b/drivers/iommu/arm-smmu-qcom.c
index ff746acd1c81..3ff62ca13ad5 100644
--- a/drivers/iommu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm-smmu-qcom.c
@@ -43,7 +43,7 @@ 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)
+       if (client && client->direct_mapping)
                iommu_request_dm_for_dev(dev);

        return 0;

-Sai

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