1 files changed, 89 insertions, 13 deletions

diff --git a/drivers/base/regmap/regmap-debugfs.c b/drivers/base/regmap/regmap-debugfs.c
index f4b9dd01c98..07aad786f81 100644
--- a/drivers/base/regmap/regmap-debugfs.c
+++ b/drivers/base/regmap/regmap-debugfs.c
@@ -56,17 +56,74 @@ static const struct file_operations regmap_name_fops = {
 	.llseek = default_llseek,
 };
 
+/*
+ * Work out where the start offset maps into register numbers, bearing
+ * in mind that we suppress hidden registers.
+ */
+static unsigned int regmap_debugfs_get_dump_start(struct regmap *map,
+						  unsigned int base,
+						  loff_t from,
+						  loff_t *pos)
+{
+	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;
+		}
+	}
+
+	/* 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;
+		}
+
+		ret = c->max;
+	}
+
+	return ret;
+}
+
 static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,
 				   unsigned int to, char __user *user_buf,
 				   size_t count, loff_t *ppos)
 {
-	int reg_len, val_len, tot_len;
 	size_t buf_pos = 0;
-	loff_t p = 0;
+	loff_t p = *ppos;
 	ssize_t ret;
 	int i;
 	char *buf;
-	unsigned int val;
+	unsigned int val, start_reg;
 
 	if (*ppos < 0 || !count)
 		return -EINVAL;
@@ -76,11 +133,18 @@ static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,
 		return -ENOMEM;
 
 	/* Calculate the length of a fixed format  */
-	reg_len = regmap_calc_reg_len(map->max_register, buf, count);
-	val_len = 2 * map->format.val_bytes;
-	tot_len = reg_len + val_len + 3;      /* : \n */
+	if (!map->debugfs_tot_len) {
+		map->debugfs_reg_len = regmap_calc_reg_len(map->max_register,
+							   buf, count);
+		map->debugfs_val_len = 2 * map->format.val_bytes;
+		map->debugfs_tot_len = map->debugfs_reg_len +
+			map->debugfs_val_len + 3;      /* : \n */
+	}
+
+	/* Work out which register we're starting at */
+	start_reg = regmap_debugfs_get_dump_start(map, from, *ppos, &p);
 
-	for (i = from; i <= to; i += map->reg_stride) {
+	for (i = start_reg; i <= to; i += map->reg_stride) {
 		if (!regmap_readable(map, i))
 			continue;
 
@@ -90,26 +154,27 @@ static ssize_t regmap_read_debugfs(struct regmap *map, unsigned int from,
 		/* If we're in the region the user is trying to read */
 		if (p >= *ppos) {
 			/* ...but not beyond it */
-			if (buf_pos >= count - 1 - tot_len)
+			if (buf_pos + 1 + map->debugfs_tot_len >= count)
 				break;
 
 			/* Format the register */
 			snprintf(buf + buf_pos, count - buf_pos, "%.*x: ",
-				 reg_len, i - from);
-			buf_pos += reg_len + 2;
+				 map->debugfs_reg_len, i - from);
+			buf_pos += map->debugfs_reg_len + 2;
 
 			/* Format the value, write all X if we can't read */
 			ret = regmap_read(map, i, &val);
 			if (ret == 0)
 				snprintf(buf + buf_pos, count - buf_pos,
-					 "%.*x", val_len, val);
+					 "%.*x", map->debugfs_val_len, val);
 			else
-				memset(buf + buf_pos, 'X', val_len);
+				memset(buf + buf_pos, 'X',
+				       map->debugfs_val_len);
 			buf_pos += 2 * map->format.val_bytes;
 
 			buf[buf_pos++] = '\n';
 		}
-		p += tot_len;
+		p += map->debugfs_tot_len;
 	}
 
 	ret = buf_pos;
@@ -272,6 +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);
@@ -320,7 +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);
 }