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);
 }