[RFC 3/3] iommu: arm-smmu: Get reference to memory controller

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@nvidia.com>

Use the memory controller framework to obtain a reference to the memory
controller to which the SMMU will make memory requests. This allows the
two drivers to properly order their probes so that the memory controller
can be programmed first.

An example where this is required is Tegra186 where the stream IDs need
to be associated with memory clients before memory requests are emitted
with the correct stream ID.

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/iommu/arm-smmu.c | 12 ++++++++++++
 drivers/iommu/arm-smmu.h |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index b18aac4c105e..8dd214244926 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -2015,6 +2015,18 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 	}
 	smmu->dev = dev;
 
+	smmu->mc = memory_controller_get(dev, NULL);
+	if (IS_ERR(smmu->mc)) {
+		err = PTR_ERR(smmu->mc);
+
+		if (err != -ENODEV) {
+			dev_err(dev, "failed to get memory controller: %d\n", err);
+			return err;
+		}
+
+		smmu->mc = NULL;
+	}
+
 	if (dev->of_node)
 		err = arm_smmu_device_dt_probe(pdev, smmu);
 	else
diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
index b19b6cae9b5e..40b6d42eb3ab 100644
--- a/drivers/iommu/arm-smmu.h
+++ b/drivers/iommu/arm-smmu.h
@@ -17,6 +17,7 @@
 #include <linux/io-64-nonatomic-hi-lo.h>
 #include <linux/io-pgtable.h>
 #include <linux/iommu.h>
+#include <linux/memory-controller.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
 #include <linux/types.h>
@@ -224,6 +225,7 @@ enum arm_smmu_implementation {
 
 struct arm_smmu_device {
 	struct device			*dev;
+	struct memory_controller	*mc;
 
 	void __iomem			*base;
 	unsigned int			numpage;
-- 
2.23.0

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