2 files changed, 63 insertions, 14 deletions

diff --git a/drivers/base/regmap/internal.h b/drivers/base/regmap/internal.h
index 1abcd27e2d0f..9c3b0e7a6c7d 100644
--- a/drivers/base/regmap/internal.h
+++ b/drivers/base/regmap/internal.h
@@ -15,10 +15,18 @@
 
 #include <linux/regmap.h>
 #include <linux/fs.h>
+#include <linux/list.h>
 
 struct regmap;
 struct regcache_ops;
 
+struct regmap_debugfs_off_cache {
+	struct list_head list;
+	off_t min;
+	off_t max;
+	unsigned int base_reg;
+};
+
 struct regmap_format {
 	size_t buf_size;
 	size_t reg_bytes;
@@ -54,6 +62,8 @@ struct regmap {
 	unsigned int debugfs_reg_len;
 	unsigned int debugfs_val_len;
 	unsigned int debugfs_tot_len;
+
+	struct list_head debugfs_off_cache;
 #endif
 
 	unsigned int max_register;
diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index 749a1dc5bbfb..07aad786f817 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -65,25 +65,53 @@ static unsigned int regmap_debugfs_get_dump_start(struct regmap *map,
 						  loff_t from,
 						  loff_t *pos)
 {
-	loff_t p = *pos;
-	unsigned int i;
-
-	for (i = base; i <= map->max_register; i += map->reg_stride) {
-		if (!regmap_readable(map, i))
-			continue;
-
-		if (regmap_precious(map, i))
-			continue;
+	struct regmap_debugfs_off_cache *c = NULL;
+	loff_t p = 0;
+	unsigned int i, ret;
+
+	/*
+	 * If we don't have a cache build one so we don't have to do a
+	 * linear scan each time.
+	 */
+	if (list_empty(&map->debugfs_off_cache)) {
+		for (i = base; i <= map->max_register; i += map->reg_stride) {
+			/* Skip unprinted registers, closing off cache entry */
+			if (!regmap_readable(map, i) ||
+			    regmap_precious(map, i)) {
+				if (c) {
+					c->max = p - 1;
+					list_add_tail(&c->list,
+						      &map->debugfs_off_cache);
+					c = NULL;
+				}
+
+				continue;
+			}
+
+			/* No cache entry?  Start a new one */
+			if (!c) {
+				c = kzalloc(sizeof(*c), GFP_KERNEL);
+				if (!c)
+					break;
+				c->min = p;
+				c->base_reg = i;
+			}
+
+			p += map->debugfs_tot_len;
+		}
+	}
 
-		if (i >= from) {
-			*pos = p;
-			return i;
+	/* Find the relevant block */
+	list_for_each_entry(c, &map->debugfs_off_cache, list) {
+		if (*pos >= c->min && *pos <= c->max) {
+			*pos = c->min;
+			return c->base_reg;
 		}
 
-		p += map->debugfs_tot_len;
+		ret = c->max;
 	}
 
-	return base;
+	return ret;
 }
 
 static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,
@@ -309,6 +337,8 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
 	struct rb_node *next;
 	struct regmap_range_node *range_node;
 
+	INIT_LIST_HEAD(&map->debugfs_off_cache);
+
 	if (name) {
 		map->debugfs_name = kasprintf(GFP_KERNEL, "%s-%s",
 					      dev_name(map->dev), name);
@@ -357,7 +387,16 @@ void regmap_debugfs_init(struct regmap *map, const char *name)
 
 void regmap_debugfs_exit(struct regmap *map)
 {
+	struct regmap_debugfs_off_cache *c;
+
 	debugfs_remove_recursive(map->debugfs);
+	while (!list_empty(&map->debugfs_off_cache)) {
+		c = list_first_entry(&map->debugfs_off_cache,
+				     struct regmap_debugfs_off_cache,
+				     list);
+		list_del(&c->list);
+		kfree(c);
+	}
 	kfree(map->debugfs_name);
 }