[PATCH v3] iommu: arm-smmu-qcom: Ensure smmu is powered up in set_ttbr0_cfg

[PATCH v3] iommu: arm-smmu-qcom: Ensure smmu is powered up in set_ttbr0_cfg

[Anna Maniscalco]

arm_smmu_write_context_bank() assumes it is being called with RPM
active, but it turns out that is not guaranteed in the path from
qcom_adreno_smmu_set_ttbr0_cfg(), so it's possible for the register
writes to get lost when configuring the context bank while the GPU is
idle, leading to page faults later.
Add the RPM calls here to make sure the SMMU is active before we touch
it.

Signed-off-by: Anna Maniscalco <anna.maniscalco2000@gmail.com>
Reviewed-by: Rob Clark <rob.clark@oss.qualcomm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
---
Changes in v3:
- Changed commit message to be more self-contained as suggested.
- Collected RBs
- Link to v2: https://lore.kernel.org/r/20260325-qcom_smmu_pmfix-v2-1-ba769a6ad0be@gmail.com

Changes in v2:
- Simplify patch by acquiring device just around the call that needs it
- Link to v1: https://lore.kernel.org/r/20260210-qcom_smmu_pmfix-v1-1-78b7143ac053@gmail.com

To: Rob Clark <robin.clark@oss.qualcomm.com>
To: Will Deacon <will@kernel.org>
To: Robin Murphy <robin.murphy@arm.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux.dev
Cc: linux-arm-msm@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
---
 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 573085349df3..cab7d110aaf5 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -231,6 +231,7 @@ static int qcom_adreno_smmu_set_ttbr0_cfg(const void *cookie,
 	struct io_pgtable *pgtable = io_pgtable_ops_to_pgtable(smmu_domain->pgtbl_ops);
 	struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
 	struct arm_smmu_cb *cb = &smmu_domain->smmu->cbs[cfg->cbndx];
+	int ret;
 
 	/* The domain must have split pagetables already enabled */
 	if (cb->tcr[0] & ARM_SMMU_TCR_EPD1)
@@ -260,8 +261,16 @@ static int qcom_adreno_smmu_set_ttbr0_cfg(const void *cookie,
 		cb->ttbr[0] |= FIELD_PREP(ARM_SMMU_TTBRn_ASID, cb->cfg->asid);
 	}
 
+	ret = pm_runtime_resume_and_get(smmu_domain->smmu->dev);
+	if (ret < 0) {
+		dev_err(smmu_domain->smmu->dev, "failed to get runtime PM: %d\n", ret);
+		return -ENODEV;
+	}
+
 	arm_smmu_write_context_bank(smmu_domain->smmu, cb->cfg->cbndx);
 
+	pm_runtime_put_autosuspend(smmu_domain->smmu->dev);
+
 	return 0;
 }
 

---
base-commit: 50c4a49f7292b33b454ea1a16c4f77d6965405dc
change-id: 20260210-qcom_smmu_pmfix-2aead2ba4e20

Best regards,
--  
Anna Maniscalco <anna.maniscalco2000@gmail.com>

Re: [PATCH v3] iommu: arm-smmu-qcom: Ensure smmu is powered up in set_ttbr0_cfg

[Will Deacon]

On Thu, 07 May 2026 17:43:15 +0200, Anna Maniscalco wrote:
> arm_smmu_write_context_bank() assumes it is being called with RPM
> active, but it turns out that is not guaranteed in the path from
> qcom_adreno_smmu_set_ttbr0_cfg(), so it's possible for the register
> writes to get lost when configuring the context bank while the GPU is
> idle, leading to page faults later.
> Add the RPM calls here to make sure the SMMU is active before we touch
> it.
> 
> [...]

Applied to iommu (arm/smmu/updates), thanks!

[1/1] iommu: arm-smmu-qcom: Ensure smmu is powered up in set_ttbr0_cfg
      https://git.kernel.org/iommu/c/8a0aab012b52

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev