[PATCH v10 08/15] iommu/arm-smmu-v3: Cache and restore MSI config

[Pranjal Shrivastava]

The SMMU's MSI configuration registers (*_IRQ_CFGn) containing target
address, data and memory attributes lose their state when the SMMU is
powered down. We'll need to cache and restore their contents to ensure
that MSIs work after the system resumes. Address this, by caching the
original `msi_msg` within the `msi_desc` when the config is first written
by `arm_smmu_write_msi_msg`. This primarily includes the target address
and data since the memory attributes are fixed.

Introduce a new helper `arm_smmu_resume_msis` which will later be called
during the driver's resume callback. The helper re-configures the IRQCFG
registers for each relevant interrupt (evtq, gerr, priq) via the new
platform_device_msi_rewrite() helper.

In addition, clear ARM_SMMU_FEAT_MSI if MSI setup fails and the driver
falls back to wired IRQs, preventing spurious MSI resume attempts.

Reviewed-by: Nicolin Chen <nicolinc at nvidia.com>
Reviewed-by: Mostafa Saleh <smostafa at google.com>
Signed-off-by: Pranjal Shrivastava <praan at google.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 32 +++++++++++++++++++++
 1 file changed, 32 insertions(+)

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 dc2fc02b5163..a8166e75db0b 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4771,6 +4771,9 @@ static void arm_smmu_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 	struct arm_smmu_device *smmu = dev_get_drvdata(dev);
 	phys_addr_t *cfg = arm_smmu_msi_cfg[desc->msi_index];
 
+	/* Cache the msi_msg for resume */
+	desc->msg = *msg;
+
 	doorbell = (((u64)msg->address_hi) << 32) | msg->address_lo;
 	doorbell &= MSI_CFG0_ADDR_MASK;
 
@@ -4779,6 +4782,31 @@ static void arm_smmu_write_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
 	writel_relaxed(ARM_SMMU_MEMATTR_DEVICE_nGnRE, smmu->base + cfg[2]);
 }
 
+static void __maybe_unused arm_smmu_resume_msis(struct arm_smmu_device *smmu)
+{
+	/* Clear the MSI address regs as they reset to unknown value */
+	writeq_relaxed(0, smmu->base + ARM_SMMU_GERROR_IRQ_CFG0);
+	writeq_relaxed(0, smmu->base + ARM_SMMU_EVTQ_IRQ_CFG0);
+
+	if (smmu->features & ARM_SMMU_FEAT_PRI)
+		writeq_relaxed(0, smmu->base + ARM_SMMU_PRIQ_IRQ_CFG0);
+
+	if (!(smmu->features & ARM_SMMU_FEAT_MSI))
+		return;
+
+	if (!smmu->dev->msi.domain) {
+		dev_err(smmu->dev, "msi_domain absent during resume\n");
+		smmu->features &= ~ARM_SMMU_FEAT_MSI;
+		return;
+	}
+
+	platform_device_msi_rewrite(smmu->dev, smmu->gerr_irq, arm_smmu_write_msi_msg);
+	platform_device_msi_rewrite(smmu->dev, smmu->evtq.q.irq, arm_smmu_write_msi_msg);
+
+	if (smmu->features & ARM_SMMU_FEAT_PRI)
+		platform_device_msi_rewrite(smmu->dev, smmu->priq.q.irq, arm_smmu_write_msi_msg);
+}
+
 static void arm_smmu_setup_msis(struct arm_smmu_device *smmu)
 {
 	int ret, nvec = ARM_SMMU_MAX_MSIS;
@@ -4798,6 +4826,7 @@ static void arm_smmu_setup_msis(struct arm_smmu_device *smmu)
 
 	if (!dev->msi.domain) {
 		dev_info(smmu->dev, "msi_domain absent - falling back to wired irqs\n");
+		smmu->features &= ~ARM_SMMU_FEAT_MSI;
 		return;
 	}
 
@@ -4805,6 +4834,7 @@ static void arm_smmu_setup_msis(struct arm_smmu_device *smmu)
 	ret = platform_device_msi_init_and_alloc_irqs(dev, nvec, arm_smmu_write_msi_msg);
 	if (ret) {
 		dev_warn(dev, "failed to allocate MSIs - falling back to wired irqs\n");
+		smmu->features &= ~ARM_SMMU_FEAT_MSI;
 		return;
 	}
 
@@ -4918,6 +4948,8 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
 
 	irq = smmu->combined_irq;
 	if (irq) {
+		/* MSIs are unsupported for combined irq cases */
+		smmu->features &= ~ARM_SMMU_FEAT_MSI;
 		/*
 		 * Cavium ThunderX2 implementation doesn't support unique irq
 		 * lines. Use a single irq line for all the SMMUv3 interrupts.
-- 
2.55.0.979.g7e5102b832-goog