[PATCH v8 1/7] iommu/arm-smmu-qcom: Enable threaded IRQ for Adreno SMMUv2/MMU500

[Connor Abbott]

The recommended flow for stall-on-fault in SMMUv2 is the following:

1. Resolve the fault.
2. Write to FSR to clear the fault bits.
3. Write RESUME to retry or fail the transaction.

MMU500 is designed with this sequence in mind. For example,
experimentally we have seen on MMU500 that writing RESUME does not clear
FSR.SS unless the original fault is cleared in FSR, so 2 must come
before 3. FSR.SS is allowed to signal a fault (and does on MMU500) so
that if we try to do 2 -> 1 -> 3 (while exiting from the fault handler
after 2) we can get duplicate faults without hacks to disable
interrupts.

However, resolving the fault typically requires lengthy operations that
can stall, like bringing in pages from disk. The only current user,
drm/msm, dumps GPU state before failing the transaction which indeed can
stall. Therefore, from now on we will require implementations that want
to use stall-on-fault to also enable threaded IRQs. Do that with the
Adreno MMU implementations.

Signed-off-by: Connor Abbott <cwabbott0 at gmail.com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
index 59d02687280e8d37b5e944619fcfe4ebd1bd6926..4d3b99babd3584ec971bef30cd533c35904fe7f5 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
@@ -585,6 +585,7 @@ static const struct arm_smmu_impl qcom_adreno_smmu_v2_impl = {
 	.alloc_context_bank = qcom_adreno_smmu_alloc_context_bank,
 	.write_sctlr = qcom_adreno_smmu_write_sctlr,
 	.tlb_sync = qcom_smmu_tlb_sync,
+	.context_fault_needs_threaded_irq = true,
 };
 
 static const struct arm_smmu_impl qcom_adreno_smmu_500_impl = {
@@ -594,6 +595,7 @@ static const struct arm_smmu_impl qcom_adreno_smmu_500_impl = {
 	.alloc_context_bank = qcom_adreno_smmu_alloc_context_bank,
 	.write_sctlr = qcom_adreno_smmu_write_sctlr,
 	.tlb_sync = qcom_smmu_tlb_sync,
+	.context_fault_needs_threaded_irq = true,
 };
 
 static struct arm_smmu_device *qcom_smmu_create(struct arm_smmu_device *smmu,

-- 
2.47.1