[PATCH v5 08/18] iommu/arm-smmu-v3: Skip remaining GERROR causes on SFM

[Nicolin Chen]

When the SMMU enters Service Failure Mode (SFM), arm_smmu_device_disable()
clears CR0 and the SMMU stops processing requests entirely. The remaining
GERROR causes (MSI write aborts, PRIQ/EVTQ aborts, CMDQ_ERR) are moot at
that point: the cmdq is dead so arm_smmu_cmdq_skip_err() would just twiddle
bookkeeping for a queue nobody's reading, and the per-cause dev_warn lines
add little diagnostic value beyond the SFM message itself.

Ack the GERROR before arm_smmu_device_disable() and return. Acking before
the multi-ms disable wait keeps a level-triggered IRQ source from re-firing
the handler. The writel+return here duplicates the non-SFM tail because a
subsequent commit will give the two paths different locking. SFM is one-way
and the SMMU does not generate new GERROR causes, so the ack is final.

Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>
---
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 3 +++
 1 file changed, 3 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 da29e523d78b7..8a4edefeec770 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2315,8 +2315,11 @@ static irqreturn_t arm_smmu_gerror_handler(int irq, void *dev)
 		 active);
 
 	if (active & GERROR_SFM_ERR) {
+		/* SMMU is being disabled, so other errors don't matter */
+		writel(gerror, smmu->base + ARM_SMMU_GERRORN);
 		dev_err(smmu->dev, "device has entered Service Failure Mode!\n");
 		arm_smmu_device_disable(smmu);
+		return IRQ_HANDLED;
 	}
 
 	if (active & GERROR_MSI_GERROR_ABT_ERR)
-- 
2.43.0