linux-kernel - [PATCH v4 5/5] iommu: arm-smmu: Get reference to memory controller

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Date:   Thu, 13 Feb 2020 17:39:59 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Arnd Bergmann <arnd@...db.de>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Joerg Roedel <joro@...tes.org>, Olof Johansson <olof@...om.net>,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 5/5] iommu: arm-smmu: Get reference to memory controller

From: Thierry Reding <treding@...dia.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@...dia.com>
---
 drivers/iommu/arm-smmu.c | 11 +++++++++++
 drivers/iommu/arm-smmu.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 16c4b87af42b..862ea55018e8 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -2109,6 +2109,17 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
 	}
 	smmu->dev = dev;
 
+	smmu->mc = devm_memory_controller_get_optional(dev, NULL);
+	if (IS_ERR(smmu->mc)) {
+		err = PTR_ERR(smmu->mc);
+
+		if (err != -EPROBE_DEFER)
+			dev_err(dev, "failed to get memory controller: %d\n",
+				err);
+
+		return err;
+	}
+
 	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 8d1cd54d82a6..d38bcd3ce447 100644
--- a/drivers/iommu/arm-smmu.h
+++ b/drivers/iommu/arm-smmu.h
@@ -18,6 +18,7 @@
 #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>
@@ -253,6 +254,7 @@ enum arm_smmu_implementation {
 
 struct arm_smmu_device {
 	struct device			*dev;
+	struct memory_controller	*mc;
 
 	void __iomem			*base;
 	unsigned int			numpage;
-- 
2.24.1