iommu/omap: Fix bus error on debugfs access of unattached IOMMU

Any debugfs access on an OMAP IOMMU that is not enabled (done during
attach) results in a bus error due to access of registers without
the clock or the reset enabled for the respective IOMMU. So, add a
check to make sure the IOMMU is enabled/attached by a client device.
This gracefully prints a "Operation not permitted" trace when the
corresponding IOMMU is not enabled.

Signed-off-by: Suman Anna <s-anna@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/omap-iommu-debug.c

@@ -24,6 +24,11 @@ static DEFINE_MUTEX(iommu_debug_lock);
 
 static struct dentry *iommu_debug_root;
 
+static inline bool is_omap_iommu_detached(struct omap_iommu *obj)
+{
+	return !obj->domain;
+}
+
 static ssize_t debug_read_regs(struct file *file, char __user *userbuf,
 			       size_t count, loff_t *ppos)
 {
@@ -31,6 +36,9 @@ static ssize_t debug_read_regs(struct file *file, char __user *userbuf,
 	char *p, *buf;
 	ssize_t bytes;
 
+	if (is_omap_iommu_detached(obj))
+		return -EPERM;
+
 	buf = kmalloc(count, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
@@ -54,6 +62,9 @@ static ssize_t debug_read_tlb(struct file *file, char __user *userbuf,
 	char *p, *buf;
 	ssize_t bytes, rest;
 
+	if (is_omap_iommu_detached(obj))
+		return -EPERM;
+
 	buf = kmalloc(count, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;
@@ -139,6 +150,9 @@ static ssize_t debug_read_pagetable(struct file *file, char __user *userbuf,
 	char *p, *buf;
 	size_t bytes;
 
+	if (is_omap_iommu_detached(obj))
+		return -EPERM;
+
 	buf = (char *)__get_free_page(GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;