[PATCH v11 01/16] iommu/arm-smmu-v3: Refactor arm_smmu_setup_irqs

[Pranjal Shrivastava <praan@google.com>]

Refactor arm_smmu_setup_irqs by splitting it into two parts, one for
registering interrupt handlers and the other one for enabling interrupt
generation in the hardware. This refactor helps in re-initialization of
hardware interrupts as part of a subsequent patch that enables runtime
power management for the arm-smmu-v3 driver.

Additionally, pass a 'resume' flag to arm_smmu_device_reset() to skip
registering IRQ handlers again during resume. On probe, handlers are
registered after queues are configured but before enabling translation.

Reviewed-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 75 +++++++++++++++------
 1 file changed, 56 insertions(+), 19 deletions(-)

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 5732f3ba0122..270e6617a19a 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4756,14 +4756,55 @@ static void arm_smmu_setup_unique_irqs(struct arm_smmu_device *smmu)
 	}
 }
 
+static void arm_smmu_enable_irqs(struct arm_smmu_device *smmu)
+{
+	int ret;
+	u32 irqen_flags = IRQ_CTRL_EVTQ_IRQEN | IRQ_CTRL_GERROR_IRQEN;
+
+	if (smmu->features & ARM_SMMU_FEAT_PRI)
+		irqen_flags |= IRQ_CTRL_PRIQ_IRQEN;
+
+	/*
+	 * Enable interrupt generation on the SMMU.
+	 * As per the ARM SMMUv3 spec section 6.3.17 (SMMU_IRQ_CTRL):
+	 *
+	 * Completion of an Update of x_IRQEN from 0 to 1 guarantees that the
+	 * MSI configuration in SMMU_x_IRQ_CFG{0,1,2} will be used for all
+	 * future MSIs generated from source x. All wired or MSI interrupts
+	 * that are triggered from a source relate to occurrences that happened
+	 * after the completion of the Update that enabled the source. It is
+	 * not permitted to trigger an interrupt that relates to an occurrence
+	 * that happened before the source was enabled, even if the source was
+	 * previously enabled at the time of the occurrence.
+	 */
+	ret = arm_smmu_write_reg_sync(smmu, irqen_flags,
+				      ARM_SMMU_IRQ_CTRL, ARM_SMMU_IRQ_CTRLACK);
+	if (ret)
+		dev_warn(smmu->dev, "failed to enable irqs\n");
+}
+
+static int arm_smmu_disable_irqs(struct arm_smmu_device *smmu)
+{
+	return arm_smmu_write_reg_sync(smmu, 0, ARM_SMMU_IRQ_CTRL,
+				       ARM_SMMU_IRQ_CTRLACK);
+}
+
 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;
 
-	/* Disable IRQs first */
-	ret = arm_smmu_write_reg_sync(smmu, 0, ARM_SMMU_IRQ_CTRL,
-				      ARM_SMMU_IRQ_CTRLACK);
+	/*
+	 * Disable IRQs first as required by the Arm SMMUv3 spec.
+	 * As per the ARM SMMUv3 spec section 6.3.17 (SMMU_IRQ_CTRL):
+	 *
+	 * An Update of x_IRQEN from 1 to 0 completes when all prior MSIs have
+	 * completed. An MSI has completed when it is visible to its
+	 * Shareability domain, or when it has aborted, and the abort is
+	 * recorded in the appropriate SMMU_(*_)GERROR bit. Completion of this
+	 * Update guarantees that no new MSI writes or wired edge events from
+	 * source x become visible until the source is re-enabled.
+	 */
+	ret = arm_smmu_disable_irqs(smmu);
 	if (ret) {
 		dev_err(smmu->dev, "failed to disable irqs\n");
 		return ret;
@@ -4785,15 +4826,6 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
 	} else
 		arm_smmu_setup_unique_irqs(smmu);
 
-	if (smmu->features & ARM_SMMU_FEAT_PRI)
-		irqen_flags |= IRQ_CTRL_PRIQ_IRQEN;
-
-	/* Enable interrupt generation on the SMMU */
-	ret = arm_smmu_write_reg_sync(smmu, irqen_flags,
-				      ARM_SMMU_IRQ_CTRL, ARM_SMMU_IRQ_CTRLACK);
-	if (ret)
-		dev_warn(smmu->dev, "failed to enable irqs\n");
-
 	return 0;
 }
 
@@ -4841,7 +4873,7 @@ static void arm_smmu_write_strtab(struct arm_smmu_device *smmu)
 	writel_relaxed(reg, smmu->base + ARM_SMMU_STRTAB_BASE_CFG);
 }
 
-static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
+static int arm_smmu_device_reset(struct arm_smmu_device *smmu, bool resume)
 {
 	int ret;
 	u32 reg, enables;
@@ -4943,12 +4975,17 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
 		}
 	}
 
-	ret = arm_smmu_setup_irqs(smmu);
-	if (ret) {
-		dev_err(smmu->dev, "failed to setup irqs\n");
-		return ret;
+	if (!resume) {
+		ret = arm_smmu_setup_irqs(smmu);
+		if (ret) {
+			dev_err(smmu->dev, "failed to setup irqs\n");
+			return ret;
+		}
 	}
 
+	/* Enable interrupt generation on the SMMU */
+	arm_smmu_enable_irqs(smmu);
+
 	if (is_kdump_kernel())
 		enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
 
@@ -5594,7 +5631,7 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 	arm_smmu_rmr_install_bypass_ste(smmu);
 
 	/* Reset the device */
-	ret = arm_smmu_device_reset(smmu);
+	ret = arm_smmu_device_reset(smmu, false);
 	if (ret) {
 		arm_smmu_device_disable(smmu);
 		return ret;
-- 
2.56.0.rc1.315.gc6ed9934b7-goog