power: supply: sc27xx: Fix capacity saving function

We found sometimes we can not get the saving capacity to initialize the
battery capacity, the reason is the user area registers are put on power
always-on region, so we need delay some time to wait until values are
updated successfully.

Moreover we also should clear the USER_AREA_CLEAR register after setting
the USER_AREA_SET register, otherwise we can not save the values in the
USER_AREA_SET register.
Signed-off-by: Yuanjiang Yu <yuanjiang.yu@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/sc27xx_fuel_gauge.c

@@ -171,10 +171,37 @@ static int sc27xx_fgu_save_boot_mode(struct sc27xx_fgu_data *data,
 	if (ret)
 		return ret;
 
+	/*
+	 * Since the user area registers are put on power always-on region,
+	 * then these registers changing time will be a little long. Thus
+	 * here we should delay 200us to wait until values are updated
+	 * successfully according to the datasheet.
+	 */
+	udelay(200);
+
+	ret = regmap_update_bits(data->regmap,
+				 data->base + SC27XX_FGU_USER_AREA_SET,
+				 SC27XX_FGU_MODE_AREA_MASK,
+				 boot_mode << SC27XX_FGU_MODE_AREA_SHIFT);
+	if (ret)
+		return ret;
+
+	/*
+	 * Since the user area registers are put on power always-on region,
+	 * then these registers changing time will be a little long. Thus
+	 * here we should delay 200us to wait until values are updated
+	 * successfully according to the datasheet.
+	 */
+	udelay(200);
+
+	/*
+	 * According to the datasheet, we should set the USER_AREA_CLEAR to 0 to
+	 * make the user area data available, otherwise we can not save the user
+	 * area data.
+	 */
 	return regmap_update_bits(data->regmap,
-				  data->base + SC27XX_FGU_USER_AREA_SET,
-				  SC27XX_FGU_MODE_AREA_MASK,
-				  boot_mode << SC27XX_FGU_MODE_AREA_SHIFT);
+				  data->base + SC27XX_FGU_USER_AREA_CLEAR,
+				  SC27XX_FGU_MODE_AREA_MASK, 0);
 }
 
 static int sc27xx_fgu_save_last_cap(struct sc27xx_fgu_data *data, int cap)
@@ -188,9 +215,36 @@ static int sc27xx_fgu_save_last_cap(struct sc27xx_fgu_data *data, int cap)
 	if (ret)
 		return ret;
 
+	/*
+	 * Since the user area registers are put on power always-on region,
+	 * then these registers changing time will be a little long. Thus
+	 * here we should delay 200us to wait until values are updated
+	 * successfully according to the datasheet.
+	 */
+	udelay(200);
+
+	ret = regmap_update_bits(data->regmap,
+				 data->base + SC27XX_FGU_USER_AREA_SET,
+				 SC27XX_FGU_CAP_AREA_MASK, cap);
+	if (ret)
+		return ret;
+
+	/*
+	 * Since the user area registers are put on power always-on region,
+	 * then these registers changing time will be a little long. Thus
+	 * here we should delay 200us to wait until values are updated
+	 * successfully according to the datasheet.
+	 */
+	udelay(200);
+
+	/*
+	 * According to the datasheet, we should set the USER_AREA_CLEAR to 0 to
+	 * make the user area data available, otherwise we can not save the user
+	 * area data.
+	 */
 	return regmap_update_bits(data->regmap,
-				  data->base + SC27XX_FGU_USER_AREA_SET,
-				  SC27XX_FGU_CAP_AREA_MASK, cap);
+				  data->base + SC27XX_FGU_USER_AREA_CLEAR,
+				  SC27XX_FGU_CAP_AREA_MASK, 0);
 }
 
 static int sc27xx_fgu_read_last_cap(struct sc27xx_fgu_data *data, int *cap)