v4.19.13 snapshot.
diff --git a/drivers/base/regmap/regcache-flat.c b/drivers/base/regmap/regcache-flat.c
new file mode 100644
index 0000000..bc6cd88
--- /dev/null
+++ b/drivers/base/regmap/regcache-flat.c
@@ -0,0 +1,87 @@
+/*
+ * Register cache access API - flat caching support
+ *
+ * Copyright 2012 Wolfson Microelectronics plc
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/device.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+#include "internal.h"
+
+static inline unsigned int regcache_flat_get_index(const struct regmap *map,
+ unsigned int reg)
+{
+ return regcache_get_index_by_order(map, reg);
+}
+
+static int regcache_flat_init(struct regmap *map)
+{
+ int i;
+ unsigned int *cache;
+
+ if (!map || map->reg_stride_order < 0 || !map->max_register)
+ return -EINVAL;
+
+ map->cache = kcalloc(regcache_flat_get_index(map, map->max_register)
+ + 1, sizeof(unsigned int), GFP_KERNEL);
+ if (!map->cache)
+ return -ENOMEM;
+
+ cache = map->cache;
+
+ for (i = 0; i < map->num_reg_defaults; i++) {
+ unsigned int reg = map->reg_defaults[i].reg;
+ unsigned int index = regcache_flat_get_index(map, reg);
+
+ cache[index] = map->reg_defaults[i].def;
+ }
+
+ return 0;
+}
+
+static int regcache_flat_exit(struct regmap *map)
+{
+ kfree(map->cache);
+ map->cache = NULL;
+
+ return 0;
+}
+
+static int regcache_flat_read(struct regmap *map,
+ unsigned int reg, unsigned int *value)
+{
+ unsigned int *cache = map->cache;
+ unsigned int index = regcache_flat_get_index(map, reg);
+
+ *value = cache[index];
+
+ return 0;
+}
+
+static int regcache_flat_write(struct regmap *map, unsigned int reg,
+ unsigned int value)
+{
+ unsigned int *cache = map->cache;
+ unsigned int index = regcache_flat_get_index(map, reg);
+
+ cache[index] = value;
+
+ return 0;
+}
+
+struct regcache_ops regcache_flat_ops = {
+ .type = REGCACHE_FLAT,
+ .name = "flat",
+ .init = regcache_flat_init,
+ .exit = regcache_flat_exit,
+ .read = regcache_flat_read,
+ .write = regcache_flat_write,
+};