[PATCH 0/2] iommu/qcom+msm: Use identity domain for display/GPU

[PATCH 0/2] iommu/qcom+msm: Use identity domain for display/GPU

[Rob Clark]

Similar to what is already done in arm-smmu-qcom, match display and GPU
compatible strings to pick identity domain type for them.

So far, we have an "evil twin" domain kicking around after drm/msm
attaches it's own domain.  Until now, that has been relatively harmless.
But it becomes a problem with [1] when we start using sg_dma_len()/
sg_dma_address() for setting up mappings.  Which is required to avoid
problems with CONFIG_DMABUF_DEBUG (dma_buf_wrap_sg_table()).

The first patch is at least compile tested.. msm_iommu seems to be
armv7-only.

If there are devices with bootloader splash, we may also need some
work on qcom_iommu_identity_attach() and/or msm_iommu_identity_attach()
to put the context bank into bypass instead of disabling it?  Not sure,
but that is probably going to require someone with such hardware at
hand.

[1] https://patchwork.freedesktop.org/series/175619/

Rob Clark (2):
  iommu/qcom: Use identity domain for GPU and display
  iommu/msm: Use identity domain for GPU and display

 drivers/iommu/arm/arm-smmu/qcom_iommu.c | 18 ++++++++++++++++++
 drivers/iommu/msm_iommu.c               | 16 ++++++++++++++++
 2 files changed, 34 insertions(+)

-- 
2.56.0

[PATCH 1/2] iommu/qcom: Use identity domain for GPU and display

[Rob Clark]

Similar to commit 0e764a01015d ("iommu/arm-smmu: Allow client devices to
select direct mapping") for arm-smmu-qcom, match GPU and display compat
strings to pick identity domain time.

The drm/msm driver attaches it's own domain, which it manages directly,
so we don't want an iommu managed domain interfering.

Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
---
 drivers/iommu/arm/arm-smmu/qcom_iommu.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
index 21d18ce67b98..5b10feb419d8 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>
@@ -589,6 +590,22 @@ static int qcom_iommu_of_xlate(struct device *dev,
 	return iommu_fwspec_add_ids(dev, &asid, 1);
 }
 
+static const struct of_device_id qcom_iommu_client_of_match[] = {
+	{ .compatible = "qcom,adreno" },
+	{ .compatible = "qcom,mdp4" },
+	{ .compatible = "qcom,mdp5" },
+	{ .compatible = "qcom,mdss" },
+	{ }
+};
+
+static int qcom_iommu_def_domain_type(struct device *dev)
+{
+	const struct of_device_id *match =
+		of_match_device(qcom_iommu_client_of_match, dev);
+
+	return match ? IOMMU_DOMAIN_IDENTITY : 0;
+}
+
 static const struct iommu_ops qcom_iommu_ops = {
 	.identity_domain = &qcom_iommu_identity_domain,
 	.capable	= qcom_iommu_capable,
@@ -596,6 +613,7 @@ static const struct iommu_ops qcom_iommu_ops = {
 	.probe_device	= qcom_iommu_probe_device,
 	.device_group	= generic_device_group,
 	.of_xlate	= qcom_iommu_of_xlate,
+	.def_domain_type = qcom_iommu_def_domain_type,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
 		.attach_dev	= qcom_iommu_attach_dev,
 		.map_pages	= qcom_iommu_map,
-- 
2.56.0

Re: [PATCH 1/2] iommu/qcom: Use identity domain for GPU and display

[Konrad Dybcio]

On 10/29/26 10:23 PM, Rob Clark wrote:
> Similar to commit 0e764a01015d ("iommu/arm-smmu: Allow client devices to
> select direct mapping") for arm-smmu-qcom, match GPU and display compat
> strings to pick identity domain time.
> 
> The drm/msm driver attaches it's own domain, which it manages directly,
> so we don't want an iommu managed domain interfering.
> 
> Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
> ---

fwiw I'm not sure we have any devices with this driver and mdp4
but anyway

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad

Re: [PATCH 1/2] iommu/qcom: Use identity domain for GPU and display

[Rob Clark]

On Fri, Oct 30, 2026 at 1:35 AM Konrad Dybcio
<konrad.dybcio@oss.qualcomm.com> wrote:
>
> On 10/29/26 10:23 PM, Rob Clark wrote:
> > Similar to commit 0e764a01015d ("iommu/arm-smmu: Allow client devices to
> > select direct mapping") for arm-smmu-qcom, match GPU and display compat
> > strings to pick identity domain time.
> >
> > The drm/msm driver attaches it's own domain, which it manages directly,
> > so we don't want an iommu managed domain interfering.
> >
> > Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
> > ---
>
> fwiw I'm not sure we have any devices with this driver and mdp4
> but anyway

probably true of arm-smmu-qcom as well ;-)

> Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
>
> Konrad

[PATCH 2/2] iommu/msm: Use identity domain for GPU and display

[Rob Clark]

Similar to commit 0e764a01015d ("iommu/arm-smmu: Allow client devices to
select direct mapping") for arm-smmu-qcom, match GPU and display compat
strings to pick identity domain time.

The drm/msm driver attaches it's own domain, which it manages directly,
so we don't want an iommu managed domain interfering.

Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
---
 drivers/iommu/msm_iommu.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c
index 4ef1e8c8244b..1c5011432628 100644
--- a/drivers/iommu/msm_iommu.c
+++ b/drivers/iommu/msm_iommu.c
@@ -12,6 +12,7 @@
 #include <linux/io.h>
 #include <linux/io-pgtable.h>
 #include <linux/interrupt.h>
+#include <linux/of_device.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
@@ -691,12 +692,27 @@ irqreturn_t msm_iommu_fault_handler(int irq, void *dev_id)
 	return 0;
 }
 
+static const struct of_device_id msm_iommu_client_of_match[] = {
+	{ .compatible = "qcom,adreno" },
+	{ .compatible = "qcom,mdp4" },
+	{ }
+};
+
+static int msm_iommu_def_domain_type(struct device *dev)
+{
+	const struct of_device_id *match =
+		of_match_device(msm_iommu_client_of_match, dev);
+
+	return match ? IOMMU_DOMAIN_IDENTITY : 0;
+}
+
 static struct iommu_ops msm_iommu_ops = {
 	.identity_domain = &msm_iommu_identity_domain,
 	.domain_alloc_paging = msm_iommu_domain_alloc_paging,
 	.probe_device = msm_iommu_probe_device,
 	.device_group = generic_device_group,
 	.of_xlate = qcom_iommu_of_xlate,
+	.def_domain_type = msm_iommu_def_domain_type,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
 		.attach_dev	= msm_iommu_attach_dev,
 		.map_pages	= msm_iommu_map,
-- 
2.56.0

Re: [PATCH 2/2] iommu/msm: Use identity domain for GPU and display

[Konrad Dybcio]

On 10/29/26 10:23 PM, Rob Clark wrote:
> Similar to commit 0e764a01015d ("iommu/arm-smmu: Allow client devices to
> select direct mapping") for arm-smmu-qcom, match GPU and display compat
> strings to pick identity domain time.
> 
> The drm/msm driver attaches it's own domain, which it manages directly,
> so we don't want an iommu managed domain interfering.
> 
> Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
> ---

Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>

Konrad