mfd: Add support for enabling tps65910 external 32-kHz oscillator

Add flag to platform data to enable external 32-kHz crystal oscillator
(or square wave) input.

The tps6591x can use either an internal 32-kHz RC oscillator or an
external crystal (or square wave) to generate the 32-kHz clock.

The default setting depends on the selected boot mode. In boot mode 00
the internal RC oscillator is used at power-on, but the external crystal
oscillator (or square wave) can be enabled by clearing the ck32k_ctrl
flag in the device control register.

Note that there is no way to switch from the external crystal oscillator
to the internal RC oscillator.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/tps65910.c

@@ -68,6 +68,25 @@ static const struct regmap_config tps65910_regmap_config = {
 	.cache_type = REGCACHE_RBTREE,
 };
 
+static int __devinit tps65910_misc_init(struct tps65910 *tps65910,
+					struct tps65910_board *pmic_pdata)
+{
+	struct device *dev = tps65910->dev;
+	int ret;
+
+	if (pmic_pdata->en_ck32k_xtal) {
+		ret = tps65910_reg_clear_bits(tps65910,
+						TPS65910_DEVCTRL,
+						DEVCTRL_CK32K_CTRL_MASK);
+		if (ret < 0) {
+			dev_err(dev, "clear ck32k_ctrl failed: %d\n", ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
 static int __devinit tps65910_sleepinit(struct tps65910 *tps65910,
 		struct tps65910_board *pmic_pdata)
 {
@@ -243,7 +262,7 @@ static __devinit int tps65910_i2c_probe(struct i2c_client *i2c,
 	init_data->irq_base = pmic_plat_data->irq_base;
 
 	tps65910_irq_init(tps65910, init_data->irq, init_data);
-
+	tps65910_misc_init(tps65910, pmic_plat_data);
 	tps65910_sleepinit(tps65910, pmic_plat_data);
 
 	return ret;

include/linux/mfd/tps65910.h

@@ -807,6 +807,7 @@ struct tps65910_board {
 	int irq_base;
 	int vmbch_threshold;
 	int vmbch2_threshold;
+	bool en_ck32k_xtal;
 	bool en_dev_slp;
 	struct tps65910_sleep_keepon_data *slp_keepon;
 	bool en_gpio_sleep[TPS6591X_MAX_NUM_GPIO];