mfd: Turn on the twl4030-madc MADC clock

Without turning the MADC clock on, no MADC conversions occur.

$ cat /sys/class/hwmon/hwmon0/device/in8_input
[   53.428436] twl4030_madc twl4030_madc: conversion timeout!
cat: read error: Resource temporarily unavailable
Signed-off-by: Kyle Manna <kyle@kylemanna.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/twl4030-madc.c

@@ -740,6 +740,28 @@ static int __devinit twl4030_madc_probe(struct platform_device *pdev)
 			TWL4030_BCI_BCICTL1);
 		goto err_i2c;
 	}
+
+	/* Check that MADC clock is on */
+	ret = twl_i2c_read_u8(TWL4030_MODULE_INTBR, &regval, TWL4030_REG_GPBR1);
+	if (ret) {
+		dev_err(&pdev->dev, "unable to read reg GPBR1 0x%X\n",
+				TWL4030_REG_GPBR1);
+		goto err_i2c;
+	}
+
+	/* If MADC clk is not on, turn it on */
+	if (!(regval & TWL4030_GPBR1_MADC_HFCLK_EN)) {
+		dev_info(&pdev->dev, "clk disabled, enabling\n");
+		regval |= TWL4030_GPBR1_MADC_HFCLK_EN;
+		ret = twl_i2c_write_u8(TWL4030_MODULE_INTBR, regval,
+				       TWL4030_REG_GPBR1);
+		if (ret) {
+			dev_err(&pdev->dev, "unable to write reg GPBR1 0x%X\n",
+					TWL4030_REG_GPBR1);
+			goto err_i2c;
+		}
+	}
+
 	platform_set_drvdata(pdev, madc);
 	mutex_init(&madc->lock);
 	ret = request_threaded_irq(platform_get_irq(pdev, 0), NULL,

include/linux/i2c/twl4030-madc.h

@@ -129,6 +129,10 @@ enum sample_type {
 #define REG_BCICTL2             0x024
 #define TWL4030_BCI_ITHSENS	0x007
 
+/* Register and bits for GPBR1 register */
+#define TWL4030_REG_GPBR1		0x0c
+#define TWL4030_GPBR1_MADC_HFCLK_EN	(1 << 7)
+
 struct twl4030_madc_user_parms {
 	int channel;
 	int average;