iommu/amd: Add basic debugfs infrastructure for AMD IOMMU

Implement a skeleton framework for debugfs support in the AMD
IOMMU.  Add an AMD-specific Kconfig boolean that depends upon
general enablement of DebugFS in the IOMMU.
Signed-off-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/Kconfig

@@ -145,6 +145,18 @@ config AMD_IOMMU_V2
 	  hardware. Select this option if you want to use devices that support
 	  the PCI PRI and PASID interface.
 
+config AMD_IOMMU_DEBUGFS
+	bool "Enable AMD IOMMU internals in DebugFS"
+	depends on AMD_IOMMU && IOMMU_DEBUGFS
+	---help---
+	  !!!WARNING!!!  !!!WARNING!!!  !!!WARNING!!!  !!!WARNING!!!
+
+	  DO NOT ENABLE THIS OPTION UNLESS YOU REALLY, -REALLY- KNOW WHAT YOU ARE DOING!!!
+	  Exposes AMD IOMMU device internals in DebugFS.
+
+	  This option is -NOT- intended for production environments, and should
+	  not generally be enabled.
+
 # Intel IOMMU support
 config DMAR_TABLE
 	bool

drivers/iommu/Makefile

@@ -11,6 +11,7 @@ obj-$(CONFIG_IOMMU_IOVA) += iova.o
 obj-$(CONFIG_OF_IOMMU)	+= of_iommu.o
 obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o
 obj-$(CONFIG_AMD_IOMMU) += amd_iommu.o amd_iommu_init.o
+obj-$(CONFIG_AMD_IOMMU_DEBUGFS) += amd_iommu_debugfs.o
 obj-$(CONFIG_AMD_IOMMU_V2) += amd_iommu_v2.o
 obj-$(CONFIG_ARM_SMMU) += arm-smmu.o
 obj-$(CONFIG_ARM_SMMU_V3) += arm-smmu-v3.o

drivers/iommu/amd_iommu_debugfs.c

+// 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 = debugfs_create_dir("amd",
+						       iommu_debugfs_dir);
+	mutex_unlock(&amd_iommu_debugfs_lock);
+
+	snprintf(name, MAX_NAME_LEN, "iommu%02d", iommu->index);
+	iommu->debugfs = debugfs_create_dir(name, amd_iommu_debugfs);
+}

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;
 }
 

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_AMD_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);

drivers/iommu/amd_iommu_types.h

@@ -594,6 +594,11 @@ struct amd_iommu {
 
 	u32 flags;
 	volatile u64 __aligned(8) cmd_sem;
+
+#ifdef CONFIG_AMD_IOMMU_DEBUGFS
+	/* DebugFS Info */
+	struct dentry *debugfs;
+#endif
 };
 
 static inline struct amd_iommu *dev_to_amd_iommu(struct device *dev)