[PATCH v4 09/15] iommu/arm-smmu-v3: Disable PRI when no IRQ handler is registered

[Nicolin Chen]

arm_smmu_setup_irqs() can leave the PRIQ without any registered handler if
its IRQ is missing, its request fails, or the combined IRQ request fails.
These paths warn but leave ARM_SMMU_FEAT_PRI set.

This function itself would then go on to enable IRQ_CTRL_PRIQ_IRQEN, even
though no handler will drain the queue. A later patch also enables PRI on
such endpoints. The caller already enabled CR0_PRIQEN before this function
even runs.

Clear ARM_SMMU_FEAT_PRI in all three failure paths, so that subsequent code
treats PRI as unavailable. And disable CR0_PRIQEN after the setup function
returns.

A kdump kernel doesn't service page requests: strip FEAT_PRI when detecting
features, so downstream PRI setup is skipped.

Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxxxxxxxx>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

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 bd7615ce69581..43a6029cef430 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4936,9 +4936,11 @@ static void arm_smmu_setup_unique_irqs(struct arm_smmu_device *smmu)
 				dev_warn(smmu->dev,
 					 "failed to enable priq irq\n");
 				smmu->priq.q.irq = 0;
+				smmu->features &= ~ARM_SMMU_FEAT_PRI;
 			}
 		} else {
 			dev_warn(smmu->dev, "no priq irq - PRI will be broken\n");
+			smmu->features &= ~ARM_SMMU_FEAT_PRI;
 		}
 	} else {
 		/* An unrequested IRQ (e.g. set by DT) must not be disabled */
@@ -4973,6 +4975,7 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
 		if (ret < 0) {
 			dev_warn(smmu->dev, "failed to enable combined irq\n");
 			smmu->combined_irq = 0;
+			smmu->features &= ~ARM_SMMU_FEAT_PRI;
 		}
 	} else
 		arm_smmu_setup_unique_irqs(smmu);
@@ -5153,6 +5156,10 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
 		return ret;
 	}
 
+	/* arm_smmu_setup_irqs() might have unset the ARM_SMMU_FEAT_PRI */
+	if (!(smmu->features & ARM_SMMU_FEAT_PRI))
+		enables &= ~CR0_PRIQEN;
+
 	if (is_kdump_kernel())
 		enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
 
@@ -5294,7 +5301,7 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
 	}
 
 	/* Boolean feature flags */
-	if (IS_ENABLED(CONFIG_PCI_PRI) && reg & IDR0_PRI)
+	if (IS_ENABLED(CONFIG_PCI_PRI) && reg & IDR0_PRI && !is_kdump_kernel())
 		smmu->features |= ARM_SMMU_FEAT_PRI;
 
 	if (IS_ENABLED(CONFIG_PCI_ATS) && reg & IDR0_ATS)
-- 
2.43.0