Re: [PATCH v11 09/16] iommu/arm-smmu-v3: Restore MSI config on resume

The SMMU's MSI configuration registers (*_IRQ_CFGn) containing target
address, data and memory attributes lose their state when the SMMU is
powered down.

Introduce arm_smmu_resume_msis() to zero the *_IRQ_CFG0 registers (which
reset to unknown values) and restore the cached MSI messages across the
device's MSI domain via msi_device_domain_restore_msi_msgs().

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 <redacted>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 13 +++++++++++++
 1 file changed, 13 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..7347d3ecdae8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -4779,6 +4779,19 @@ 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);