iommu/arm-smmu: Add system PM support

With all our hardware state tracked in such a way that we can naturally
restore it as part of the necessary reset, resuming is trivial, and
there's nothing to do on suspend at all.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/iommu/arm-smmu.c

@@ -2372,10 +2372,21 @@ static void arm_smmu_device_shutdown(struct platform_device *pdev)
 	arm_smmu_device_remove(pdev);
 }
 
+static int __maybe_unused arm_smmu_pm_resume(struct device *dev)
+{
+	struct arm_smmu_device *smmu = dev_get_drvdata(dev);
+
+	arm_smmu_device_reset(smmu);
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(arm_smmu_pm_ops, NULL, arm_smmu_pm_resume);
+
 static struct platform_driver arm_smmu_driver = {
 	.driver	= {
 		.name		= "arm-smmu",
 		.of_match_table	= of_match_ptr(arm_smmu_of_match),
+		.pm		= &arm_smmu_pm_ops,
 	},
 	.probe	= arm_smmu_device_probe,
 	.remove	= arm_smmu_device_remove,