linux-kernel - [PATCH 4/6] iommu/arm-smmu: Allow using a threaded handler for context interrupts

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Date:   Wed, 18 Oct 2023 19:19:21 -0700
From:   Georgi Djakov <quic_c_gdjako@...cinc.com>
To:     <robh+dt@...nel.org>, <krzysztof.kozlowski+dt@...aro.org>,
        <conor+dt@...nel.org>, <will@...nel.org>, <robin.murphy@....com>,
        <joro@...tes.org>
CC:     <devicetree@...r.kernel.org>, <andersson@...nel.org>,
        <konrad.dybcio@...aro.org>, <linux-arm-kernel@...ts.infradead.org>,
        <iommu@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <quic_cgoldswo@...cinc.com>,
        <quic_sukadev@...cinc.com>, <quic_pdaly@...cinc.com>,
        <quic_sudaraja@...cinc.com>, <djakov@...nel.org>
Subject: [PATCH 4/6] iommu/arm-smmu: Allow using a threaded handler for context interrupts

Threaded IRQ handlers run in a less critical context compared to normal IRQs,
so they can perform more complex and time-consuming operations without causing
significant delays in other parts of the kernel.
During a context fault, it might be needed to do more processing and gather
debug information from TBUs in the handler. These operations may sleep, so
add an option to use a threaded IRQ handler in these cases.

Signed-off-by: Georgi Djakov <quic_c_gdjako@...cinc.com>
---
 drivers/iommu/arm/arm-smmu/arm-smmu.c | 12 ++++++++++--
 drivers/iommu/arm/arm-smmu/arm-smmu.h |  1 +
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index d6d1a2a55cc0..a6561bb245ad 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -796,8 +796,16 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
 	else
 		context_fault = arm_smmu_context_fault;
 
-	ret = devm_request_irq(smmu->dev, irq, context_fault,
-			       IRQF_SHARED, "arm-smmu-context-fault", domain);
+	if (smmu->impl && smmu->impl->context_fault_needs_threaded_irq)
+		ret = devm_request_threaded_irq(smmu->dev, irq, NULL,
+						context_fault,
+						IRQF_ONESHOT | IRQF_SHARED,
+						"arm-smmu-context-fault",
+						domain);
+	else
+		ret = devm_request_irq(smmu->dev, irq, context_fault,
+				       IRQF_SHARED, "arm-smmu-context-fault", domain);
+
 	if (ret < 0) {
 		dev_err(smmu->dev, "failed to request context IRQ %d (%u)\n",
 			cfg->irptndx, irq);
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
index e5df65c0f81a..09f11f942ff8 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
@@ -439,6 +439,7 @@ struct arm_smmu_impl {
 	int (*def_domain_type)(struct device *dev);
 	irqreturn_t (*global_fault)(int irq, void *dev);
 	irqreturn_t (*context_fault)(int irq, void *dev);
+	bool context_fault_needs_threaded_irq;
 	int (*alloc_context_bank)(struct arm_smmu_domain *smmu_domain,
 				  struct arm_smmu_device *smmu,
 				  struct device *dev, int start);