3 files changed, 110 insertions, 11 deletions

diff --git a/drivers/base/regmap/regmap-i2c.c b/drivers/base/regmap/regmap-i2c.c
index ca193d1ef47c..053150a7f9f2 100644
--- a/drivers/base/regmap/regmap-i2c.c
+++ b/drivers/base/regmap/regmap-i2c.c
@@ -168,6 +168,8 @@ static struct regmap_bus regmap_i2c = {
         .write = regmap_i2c_write,
         .gather_write = regmap_i2c_gather_write,
         .read = regmap_i2c_read,
+        .reg_format_endian_default = REGMAP_ENDIAN_BIG,
+        .val_format_endian_default = REGMAP_ENDIAN_BIG,
 };
 
 static const struct regmap_bus *regmap_get_i2c_bus(struct i2c_client *i2c,
diff --git a/drivers/base/regmap/regmap-spi.c b/drivers/base/regmap/regmap-spi.c
index 0eb3097c0d76..53d1148e80a0 100644
--- a/drivers/base/regmap/regmap-spi.c
+++ b/drivers/base/regmap/regmap-spi.c
@@ -109,6 +109,8 @@ static struct regmap_bus regmap_spi = {
         .async_alloc = regmap_spi_async_alloc,
         .read = regmap_spi_read,
         .read_flag_mask = 0x80,
+        .reg_format_endian_default = REGMAP_ENDIAN_BIG,
+        .val_format_endian_default = REGMAP_ENDIAN_BIG,
 };
 
 /**
diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index 78f43fb2fe84..e4e567e82b84 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -15,6 +15,7 @@
 #include <linux/export.h>
 #include <linux/mutex.h>
 #include <linux/err.h>
+#include <linux/of.h>
 #include <linux/rbtree.h>
 #include <linux/sched.h>
 
@@ -448,6 +449,102 @@ int regmap_attach_dev(struct device *dev, struct regmap *map,
 }
 EXPORT_SYMBOL_GPL(regmap_attach_dev);
 
+enum regmap_endian_type {
+        REGMAP_ENDIAN_REG,
+        REGMAP_ENDIAN_VAL,
+};
+
+static int of_regmap_get_endian(struct device *dev,
+                                const struct regmap_bus *bus,
+                                const struct regmap_config *config,
+                                enum regmap_endian_type type,
+                                enum regmap_endian *endian)
+{
+        struct device_node *np = dev->of_node;
+
+        if (!endian || !config)
+                return -EINVAL;
+
+        /*
+         * Firstly, try to parse the endianness from driver's config,
+         * this is to be compatible with the none DT or the old drivers.
+         * From the driver's config the endianness value maybe:
+         *   REGMAP_ENDIAN_BIG,
+         *   REGMAP_ENDIAN_LITTLE,
+         *   REGMAP_ENDIAN_NATIVE,
+         *   REGMAP_ENDIAN_DEFAULT.
+         */
+        switch (type) {
+        case REGMAP_ENDIAN_REG:
+                *endian = config->reg_format_endian;
+                break;
+        case REGMAP_ENDIAN_VAL:
+                *endian = config->val_format_endian;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        /*
+         * If the endianness parsed from driver config is
+         * REGMAP_ENDIAN_DEFAULT, that means maybe we are using the DT
+         * node to specify the endianness information.
+         */
+        if (*endian != REGMAP_ENDIAN_DEFAULT)
+                return 0;
+
+        /*
+         * Secondly, try to parse the endianness from DT node if the
+         * driver config does not specify it.
+         * From the DT node the endianness value maybe:
+         *   REGMAP_ENDIAN_BIG,
+         *   REGMAP_ENDIAN_LITTLE,
+         *   REGMAP_ENDIAN_NATIVE,
+         */
+        switch (type) {
+        case REGMAP_ENDIAN_VAL:
+                if (of_property_read_bool(np, "big-endian"))
+                        *endian = REGMAP_ENDIAN_BIG;
+                else if (of_property_read_bool(np, "little-endian"))
+                        *endian = REGMAP_ENDIAN_LITTLE;
+                else
+                        *endian = REGMAP_ENDIAN_NATIVE;
+                break;
+        case REGMAP_ENDIAN_REG:
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        /*
+         * If the endianness parsed from DT node is REGMAP_ENDIAN_NATIVE, that
+         * maybe means the DT does not care the endianness or it should use
+         * the regmap bus's default endianness, then we should try to check
+         * whether the regmap bus has specified the default endianness.
+         */
+        if (*endian != REGMAP_ENDIAN_NATIVE)
+                return 0;
+
+        /*
+         * Finally, try to parse the endianness from regmap bus config
+         * if in device's DT node the endianness property is absent.
+         */
+        switch (type) {
+        case REGMAP_ENDIAN_REG:
+                if (bus && bus->reg_format_endian_default)
+                        *endian = bus->reg_format_endian_default;
+                break;
+        case REGMAP_ENDIAN_VAL:
+                if (bus && bus->val_format_endian_default)
+                        *endian = bus->val_format_endian_default;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
 /**
  * regmap_init(): Initialise register map
  *
@@ -551,17 +648,15 @@ struct regmap *regmap_init(struct device *dev,
                 map->reg_read  = _regmap_bus_read;
         }
 
-        reg_endian = config->reg_format_endian;
-        if (reg_endian == REGMAP_ENDIAN_DEFAULT)
-                reg_endian = bus->reg_format_endian_default;
-        if (reg_endian == REGMAP_ENDIAN_DEFAULT)
-                reg_endian = REGMAP_ENDIAN_BIG;
-
-        val_endian = config->val_format_endian;
-        if (val_endian == REGMAP_ENDIAN_DEFAULT)
-                val_endian = bus->val_format_endian_default;
-        if (val_endian == REGMAP_ENDIAN_DEFAULT)
-                val_endian = REGMAP_ENDIAN_BIG;
+        ret = of_regmap_get_endian(dev, bus, config, REGMAP_ENDIAN_REG,
+                                   &reg_endian);
+        if (ret)
+                return ERR_PTR(ret);
+
+        ret = of_regmap_get_endian(dev, bus, config, REGMAP_ENDIAN_VAL,
+                                   &val_endian);
+        if (ret)
+                return ERR_PTR(ret);
 
         switch (config->reg_bits + map->reg_shift) {
         case 2: