regmap: add regmap_update_bits() helper

Add the regmap_update_bits() to simply the read/modify/write of registers
in a single command. The function is taken from Linux regmap
implementation.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/core/regmap.c

@@ -132,3 +132,17 @@ int regmap_write(struct regmap *map, uint offset, uint val)
 
 	return 0;
 }
+
+int regmap_update_bits(struct regmap *map, uint offset, uint mask, uint val)
+{
+	uint reg;
+	int ret;
+
+	ret = regmap_read(map, offset, &reg);
+	if (ret)
+		return ret;
+
+	reg &= ~mask;
+
+	return regmap_write(map, offset, reg | val);
+}

include/regmap.h

@@ -43,6 +43,16 @@ int regmap_read(struct regmap *map, uint offset, uint *valp);
 	regmap_read(map, (uint32_t *)(ptr)->member - (uint32_t *)(ptr), valp)
 
 /**
+ * regmap_update_bits() - Perform a read/modify/write using a mask
+ *
+ * @map:	The map returned by regmap_init_mem*()
+ * @offset:	Offset of the memory
+ * @mask:	Mask to apply to the read value
+ * @val:	Value to apply to the value to write
+ */
+int regmap_update_bits(struct regmap *map, uint offset, uint mask, uint val);
+
+/**
  * regmap_init_mem() - Set up a new register map that uses memory access
  *
  * Use regmap_uninit() to free it.