[RFC PATCH] iommu/arm-smmu: Remove shutdown callback

[Sai Prakash Ranjan]

Remove SMMU shutdown callback since it seems to cause more
problems than benefits. With this callback, we need to make
sure that all clients/consumers of SMMU do not perform any
DMA activity once the SMMU is shutdown and translation is
disabled. In other words we need to add shutdown callbacks
for all those clients to make sure they do not perform any
DMA or else we see all kinds of weird crashes during reboot
or shutdown. This is clearly not scalable as the number of
clients of SMMU would vary across SoCs and we would need to
add shutdown callbacks to almost all drivers eventually.
This callback was added for kexec usecase where it was known
to cause memory corruptions when SMMU was not shutdown but
that does not directly relate to SMMU because the memory
corruption could be because of the client of SMMU which is
not shutdown properly before booting into new kernel. So in
that case, we need to identify the client of SMMU causing
the memory corruption and add appropriate shutdown callback
to the client rather than to the SMMU.

Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@xxxxxxxxxxxxxx>
---
 drivers/iommu/arm-smmu-v3.c | 6 ------
 drivers/iommu/arm-smmu.c    | 6 ------
 2 files changed, 12 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 8a908c50c306..634da02fef78 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -4142,11 +4142,6 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static void arm_smmu_device_shutdown(struct platform_device *pdev)
-{
-	arm_smmu_device_remove(pdev);
-}
-
 static const struct of_device_id arm_smmu_of_match[] = {
 	{ .compatible = "arm,smmu-v3", },
 	{ },
@@ -4161,7 +4156,6 @@ static struct platform_driver arm_smmu_driver = {
 	},
 	.probe	= arm_smmu_device_probe,
 	.remove	= arm_smmu_device_remove,
-	.shutdown = arm_smmu_device_shutdown,
 };
 module_platform_driver(arm_smmu_driver);
 
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 243bc4cb2705..4d80516c789f 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -2276,11 +2276,6 @@ static int arm_smmu_device_remove(struct platform_device *pdev)
 	return 0;
 }
 
-static void arm_smmu_device_shutdown(struct platform_device *pdev)
-{
-	arm_smmu_device_remove(pdev);
-}
-
 static int __maybe_unused arm_smmu_runtime_resume(struct device *dev)
 {
 	struct arm_smmu_device *smmu = dev_get_drvdata(dev);
@@ -2335,7 +2330,6 @@ static struct platform_driver arm_smmu_driver = {
 	},
 	.probe	= arm_smmu_device_probe,
 	.remove	= arm_smmu_device_remove,
-	.shutdown = arm_smmu_device_shutdown,
 };
 module_platform_driver(arm_smmu_driver);
 
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