[PATCH 2/3] iommu/qcom: Use identity default domains for the MSM GPU and display

[Rob Clark]

On Fri, Oct 30, 2026 at 3:05 PM Dmitry Baryshkov
<dmitry.baryshkov at oss.qualcomm.com> wrote:
>
> drm/msm writes the addresses dma_map_sgtable() returns for the DRM
> device into its own page tables, so they have to be physical addresses,
> i.e. the device must not use iommu-dma. qcom_iommu has no
> def_domain_type, so the MDP5 and Adreno devices do get iommu-dma, the
> buffers end up mapped at IOVAs of the unused default domain and the
> db410c GPU fails to start.
>
> Use identity default domains for these devices, as arm-smmu-qcom does.
>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com>

Reviewed-by: Rob Clark <rob.clark at oss.qualcomm.com>

> ---
>  drivers/iommu/arm/arm-smmu/qcom_iommu.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> index 54130c32056a..4a9c4cf63724 100644
> --- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> +++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> @@ -22,6 +22,7 @@
>  #include <linux/init.h>
>  #include <linux/mutex.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm.h>
> @@ -531,6 +532,18 @@ static bool qcom_iommu_capable(struct device *dev, enum iommu_cap cap)
>         }
>  }
>
> +static const struct of_device_id qcom_iommu_client_of_match[] = {
> +       { .compatible = "qcom,adreno" },
> +       { .compatible = "qcom,mdp5" },
> +       { }
> +};
> +
> +static int qcom_iommu_def_domain_type(struct device *dev)
> +{
> +       return of_match_device(qcom_iommu_client_of_match, dev) ?
> +               IOMMU_DOMAIN_IDENTITY : 0;
> +}
> +
>  static struct iommu_device *qcom_iommu_probe_device(struct device *dev)
>  {
>         struct qcom_iommu_dev *qcom_iommu = dev_iommu_priv_get(dev);
> @@ -602,6 +615,7 @@ static const struct iommu_ops qcom_iommu_ops = {
>         .capable        = qcom_iommu_capable,
>         .domain_alloc_paging = qcom_iommu_domain_alloc_paging,
>         .probe_device   = qcom_iommu_probe_device,
> +       .def_domain_type = qcom_iommu_def_domain_type,
>         .device_group   = generic_device_group,
>         .of_xlate       = qcom_iommu_of_xlate,
>         .default_domain_ops = &(const struct iommu_domain_ops) {
>
> --
> 2.47.3
>