[PATCH v10 03/13] iommu/arm-smmu-v3: Add ARM_SMMU_FEAT_EVTQ for the event queue

[Nicolin Chen <nicolinc@nvidia.com>]

The driver programs and enables the event queue unconditionally, while the
PRI queue has an ARM_SMMU_FEAT_PRI gating each of its touch points. Yet a
kdump kernel wants to leave both of the queues alone, which would take an
is_kdump_kernel() test at every one of those places.

Add an ARM_SMMU_FEAT_EVTQ that the probe always sets, as the event queue is
architecturally mandatory, and gate the queue's allocation, its interrupt
and its CR0 and IRQ_CTRL enables on it, so that a later change can turn the
queue off in a single place.

No functional change intended.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Suggested-by: Robin Murphy <robin.murphy@arm.com>
Assisted-by: Claude:claude-opus-5
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  1 +
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 79 +++++++++++++--------
 2 files changed, 52 insertions(+), 28 deletions(-)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index fd6f489cfedf2..75e768b3d66d8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -927,6 +927,7 @@ struct arm_smmu_device {
 #define ARM_SMMU_FEAT_BBML2		(1 << 24)
 #define ARM_SMMU_FEAT_HAFT		(1 << 25)
 #define ARM_SMMU_FEAT_DS		(1 << 26)
+#define ARM_SMMU_FEAT_EVTQ		(1 << 27)
 	u32				features;
 
 #define ARM_SMMU_OPT_SKIP_PREFETCH	(1 << 0)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index c1d04f84870f6..c776fdd43325d 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2349,7 +2349,8 @@ static irqreturn_t arm_smmu_combined_irq_thread(int irq, void *dev)
 {
 	struct arm_smmu_device *smmu = dev;
 
-	arm_smmu_evtq_thread(irq, dev);
+	if (smmu->features & ARM_SMMU_FEAT_EVTQ)
+		arm_smmu_evtq_thread(irq, dev);
 	if (smmu->features & ARM_SMMU_FEAT_PRI)
 		arm_smmu_priq_thread(irq, dev);
 
@@ -2358,7 +2359,12 @@ static irqreturn_t arm_smmu_combined_irq_thread(int irq, void *dev)
 
 static irqreturn_t arm_smmu_combined_irq_handler(int irq, void *dev)
 {
-	arm_smmu_gerror_handler(irq, dev);
+	struct arm_smmu_device *smmu = dev;
+	irqreturn_t ret = arm_smmu_gerror_handler(irq, dev);
+
+	/* Without either queue, the thread would have nothing to drain */
+	if (!(smmu->features & (ARM_SMMU_FEAT_EVTQ | ARM_SMMU_FEAT_PRI)))
+		return ret;
 	return IRQ_WAKE_THREAD;
 }
 
@@ -4505,11 +4511,14 @@ static int arm_smmu_init_queues(struct arm_smmu_device *smmu)
 		return ret;
 
 	/* evtq */
-	ret = arm_smmu_init_one_queue(smmu, &smmu->evtq.q, smmu->page1,
-				      ARM_SMMU_EVTQ_PROD, ARM_SMMU_EVTQ_CONS,
-				      EVTQ_ENT_DWORDS, "evtq");
-	if (ret)
-		return ret;
+	if (smmu->features & ARM_SMMU_FEAT_EVTQ) {
+		ret = arm_smmu_init_one_queue(smmu, &smmu->evtq.q, smmu->page1,
+					      ARM_SMMU_EVTQ_PROD,
+					      ARM_SMMU_EVTQ_CONS,
+					      EVTQ_ENT_DWORDS, "evtq");
+		if (ret)
+			return ret;
+	}
 
 	if ((smmu->features & ARM_SMMU_FEAT_SVA) &&
 	    (smmu->features & ARM_SMMU_FEAT_STALLS)) {
@@ -4729,16 +4738,20 @@ static void arm_smmu_setup_unique_irqs(struct arm_smmu_device *smmu)
 	arm_smmu_setup_msis(smmu);
 
 	/* Request interrupt lines */
-	irq = smmu->evtq.q.irq;
-	if (irq) {
-		ret = devm_request_threaded_irq(smmu->dev, irq, NULL,
-						arm_smmu_evtq_thread,
-						IRQF_ONESHOT,
-						"arm-smmu-v3-evtq", smmu);
-		if (ret < 0)
-			dev_warn(smmu->dev, "failed to enable evtq irq\n");
-	} else {
-		dev_warn(smmu->dev, "no evtq irq - events will not be reported!\n");
+	if (smmu->features & ARM_SMMU_FEAT_EVTQ) {
+		irq = smmu->evtq.q.irq;
+		if (irq) {
+			ret = devm_request_threaded_irq(smmu->dev, irq, NULL,
+							arm_smmu_evtq_thread,
+							IRQF_ONESHOT,
+							"arm-smmu-v3-evtq", smmu);
+			if (ret < 0)
+				dev_warn(smmu->dev,
+					 "failed to enable evtq irq\n");
+		} else {
+			dev_warn(smmu->dev,
+				 "no evtq irq - events will not be reported!\n");
+		}
 	}
 
 	irq = smmu->gerr_irq;
@@ -4771,7 +4784,7 @@ static void arm_smmu_setup_unique_irqs(struct arm_smmu_device *smmu)
 static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
 {
 	int ret, irq;
-	u32 irqen_flags = IRQ_CTRL_EVTQ_IRQEN | IRQ_CTRL_GERROR_IRQEN;
+	u32 irqen_flags = IRQ_CTRL_GERROR_IRQEN;
 
 	/* Disable IRQs first */
 	ret = arm_smmu_write_reg_sync(smmu, 0, ARM_SMMU_IRQ_CTRL,
@@ -4797,6 +4810,8 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
 	} else
 		arm_smmu_setup_unique_irqs(smmu);
 
+	if (smmu->features & ARM_SMMU_FEAT_EVTQ)
+		irqen_flags |= IRQ_CTRL_EVTQ_IRQEN;
 	if (smmu->features & ARM_SMMU_FEAT_PRI)
 		irqen_flags |= IRQ_CTRL_PRIQ_IRQEN;
 
@@ -4915,16 +4930,21 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
 		smmu, arm_smmu_make_cmd_op(CMDQ_OP_TLBI_NSNH_ALL));
 
 	/* Event queue */
-	writeq_relaxed(smmu->evtq.q.q_base, smmu->base + ARM_SMMU_EVTQ_BASE);
-	writel_relaxed(smmu->evtq.q.llq.prod, smmu->page1 + ARM_SMMU_EVTQ_PROD);
-	writel_relaxed(smmu->evtq.q.llq.cons, smmu->page1 + ARM_SMMU_EVTQ_CONS);
-
-	enables |= CR0_EVTQEN;
-	ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0,
-				      ARM_SMMU_CR0ACK);
-	if (ret) {
-		dev_err(smmu->dev, "failed to enable event queue\n");
-		return ret;
+	if (smmu->features & ARM_SMMU_FEAT_EVTQ) {
+		writeq_relaxed(smmu->evtq.q.q_base,
+			       smmu->base + ARM_SMMU_EVTQ_BASE);
+		writel_relaxed(smmu->evtq.q.llq.prod,
+			       smmu->page1 + ARM_SMMU_EVTQ_PROD);
+		writel_relaxed(smmu->evtq.q.llq.cons,
+			       smmu->page1 + ARM_SMMU_EVTQ_CONS);
+
+		enables |= CR0_EVTQEN;
+		ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0,
+					      ARM_SMMU_CR0ACK);
+		if (ret) {
+			dev_err(smmu->dev, "failed to enable event queue\n");
+			return ret;
+		}
 	}
 
 	/* PRI queue */
@@ -5063,6 +5083,9 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 	u32 reg;
 	bool coherent = smmu->features & ARM_SMMU_FEAT_COHERENCY;
 
+	/* The event queue is architecturally mandatory, unlike the PRI queue */
+	smmu->features |= ARM_SMMU_FEAT_EVTQ;
+
 	/* IDR0 */
 	reg = readl_relaxed(smmu->base + ARM_SMMU_IDR0);
 
-- 
2.43.0