mfd: twl6040: Optional clk32k clock handling

In certain boards the source for the clk32k clock can be gated. In these
boards the clk32k clock can be provided to the driver and it is going to be
enabled/disabled when it is needed.
If the clk32k clock is not provided the driver will assume that it is always
running.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/twl6040.txt

@@ -19,6 +19,8 @@ Required properties:
 
 Optional properties, nodes:
 - enable-active-high: To power on the twl6040 during boot.
+- clocks: phandle to the clk32k clock provider
+- clock-names: Must be "clk32k"
 
 Vibra functionality
 Required properties:

drivers/mfd/twl6040.c

@@ -291,6 +291,8 @@ int twl6040_power(struct twl6040 *twl6040, int on)
 		if (twl6040->power_count++)
 			goto out;
 
+		clk_prepare_enable(twl6040->clk32k);
+
 		/* Allow writes to the chip */
 		regcache_cache_only(twl6040->regmap, false);
 
@@ -346,6 +348,8 @@ int twl6040_power(struct twl6040 *twl6040, int on)
 
 		twl6040->sysclk = 0;
 		twl6040->mclk = 0;
+
+		clk_disable_unprepare(twl6040->clk32k);
 	}
 
 out:
@@ -644,6 +648,12 @@ static int twl6040_probe(struct i2c_client *client,
 
 	i2c_set_clientdata(client, twl6040);
 
+	twl6040->clk32k = devm_clk_get(&client->dev, "clk32k");
+	if (IS_ERR(twl6040->clk32k)) {
+		dev_info(&client->dev, "clk32k is not handled\n");
+		twl6040->clk32k = NULL;
+	}
+
 	twl6040->supplies[0].supply = "vio";
 	twl6040->supplies[1].supply = "v2v1";
 	ret = devm_regulator_bulk_get(&client->dev, TWL6040_NUM_SUPPLIES,

include/linux/mfd/twl6040.h

@@ -28,6 +28,7 @@
 #include <linux/interrupt.h>
 #include <linux/mfd/core.h>
 #include <linux/regulator/consumer.h>
+#include <linux/clk.h>
 
 #define TWL6040_REG_ASICID		0x01
 #define TWL6040_REG_ASICREV		0x02
@@ -223,6 +224,7 @@ struct twl6040 {
 	struct regmap *regmap;
 	struct regmap_irq_chip_data *irq_data;
 	struct regulator_bulk_data supplies[2]; /* supplies for vio, v2v1 */
+	struct clk *clk32k;
 	struct mutex mutex;
 	struct mutex irq_mutex;
 	struct mfd_cell cells[TWL6040_CELLS];