[PATCH v7 2/2] iommu/amd: Add basic debugfs infrastructure for AMD IOMMU

[Gary R Hook <gary.hook@amd.com>]

Implement a skeleton framework for debugfs support in the
AMD IOMMU.

Signed-off-by: Gary R Hook <gary.hook@amd.com>
---
 drivers/iommu/Makefile            |    5 +++++
 drivers/iommu/amd_iommu_debugfs.c |   39 +++++++++++++++++++++++++++++++++++++
 drivers/iommu/amd_iommu_init.c    |    6 ++++--
 drivers/iommu/amd_iommu_proto.h   |    6 ++++++
 drivers/iommu/amd_iommu_types.h   |    3 +++
 5 files changed, 57 insertions(+), 2 deletions(-)
 create mode 100644 drivers/iommu/amd_iommu_debugfs.c

diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index 74cfbc392862..dd980f7dd8b6 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -30,3 +30,8 @@ obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
 obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
 obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
 obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
+
+# This ensures that only the required files are compiled
+ifeq ($(CONFIG_IOMMU_DEBUGFS), y)
+obj-$(CONFIG_AMD_IOMMU) += amd_iommu_debugfs.o
+endif
diff --git a/drivers/iommu/amd_iommu_debugfs.c b/drivers/iommu/amd_iommu_debugfs.c
new file mode 100644
index 000000000000..6dff98552969
--- /dev/null
+++ b/drivers/iommu/amd_iommu_debugfs.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AMD IOMMU driver
+ *
+ * Copyright (C) 2018 Advanced Micro Devices, Inc.
+ *
+ * Author: Gary R Hook <gary.hook@amd.com>
+ */
+
+#include <linux/debugfs.h>
+#include <linux/iommu.h>
+#include <linux/pci.h>
+#include "amd_iommu_proto.h"
+#include "amd_iommu_types.h"
+
+static struct dentry *amd_iommu_debugfs;
+static DEFINE_MUTEX(amd_iommu_debugfs_lock);
+
+#define	MAX_NAME_LEN	20
+
+void amd_iommu_debugfs_setup(struct amd_iommu *iommu)
+{
+	char name[MAX_NAME_LEN + 1];
+
+	mutex_lock(&amd_iommu_debugfs_lock);
+	if (!amd_iommu_debugfs)
+		amd_iommu_debugfs = iommu_debugfs_new_driver_dir("amd");
+	mutex_unlock(&amd_iommu_debugfs_lock);
+
+	if (amd_iommu_debugfs) {
+		snprintf(name, MAX_NAME_LEN, "iommu%02d", iommu->index);
+		iommu->debugfs = debugfs_create_dir(name,
+						    amd_iommu_debugfs);
+		if (!iommu->debugfs) {
+			debugfs_remove_recursive(amd_iommu_debugfs);
+			amd_iommu_debugfs = NULL;
+		}
+	}
+}
diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
index 904c575d1677..031e6dbb8345 100644
--- a/drivers/iommu/amd_iommu_init.c
+++ b/drivers/iommu/amd_iommu_init.c
@@ -2721,6 +2721,7 @@ int __init amd_iommu_enable_faulting(void)
  */
 static int __init amd_iommu_init(void)
 {
+	struct amd_iommu *iommu;
 	int ret;
 
 	ret = iommu_go_to_state(IOMMU_INITIALIZED);
@@ -2730,14 +2731,15 @@ static int __init amd_iommu_init(void)
 			disable_iommus();
 			free_iommu_resources();
 		} else {
-			struct amd_iommu *iommu;
-
 			uninit_device_table_dma();
 			for_each_iommu(iommu)
 				iommu_flush_all_caches(iommu);
 		}
 	}
 
+	for_each_iommu(iommu)
+		amd_iommu_debugfs_setup(iommu);
+
 	return ret;
 }
 
diff --git a/drivers/iommu/amd_iommu_proto.h b/drivers/iommu/amd_iommu_proto.h
index 640c286a0ab9..39053f11dda3 100644
--- a/drivers/iommu/amd_iommu_proto.h
+++ b/drivers/iommu/amd_iommu_proto.h
@@ -33,6 +33,12 @@ extern void amd_iommu_uninit_devices(void);
 extern void amd_iommu_init_notifier(void);
 extern int amd_iommu_init_api(void);
 
+#ifdef CONFIG_IOMMU_DEBUGFS
+void amd_iommu_debugfs_setup(struct amd_iommu *iommu);
+#else
+static inline void amd_iommu_debugfs_setup(struct amd_iommu *iommu) {}
+#endif
+
 /* Needed for interrupt remapping */
 extern int amd_iommu_prepare(void);
 extern int amd_iommu_enable(void);
diff --git a/drivers/iommu/amd_iommu_types.h b/drivers/iommu/amd_iommu_types.h
index 1c9b080276c9..2ca0959ae9e6 100644
--- a/drivers/iommu/amd_iommu_types.h
+++ b/drivers/iommu/amd_iommu_types.h
@@ -593,6 +593,9 @@ struct amd_iommu {
 
 	u32 flags;
 	volatile u64 __aligned(8) cmd_sem;
+
+	/* DebugFS Info */
+	struct dentry *debugfs;
 };
 
 static inline struct amd_iommu *dev_to_amd_iommu(struct device *dev)