thermal: imx: correct suspend/resume flow

Fixes regression introduced by:

commit 37713a1e
Author: Philipp Zabel <p.zabel@pengutronix.de>
Date:   Thu Aug 1 18:33:12 2013 +0200

    thermal: imx: implement thermal alarm interrupt handling

The commit 37713a1e makes imx thermal sensor always powered up as alarm
function is enabled, but the suspend callback of imx thermal returns
success only if thermal sensor is powered down, so it will always returns
fail hence break system's suspend, this patch disables imx thermal sensor
before suspend and re-enable it after resume.
Signed-off-by: Anson Huang <b20788@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/imx_thermal.c

@@ -490,27 +490,30 @@ static int imx_thermal_suspend(struct device *dev)
 {
 	struct imx_thermal_data *data = dev_get_drvdata(dev);
 	struct regmap *map = data->tempmon;
-	u32 val;
 
-	regmap_read(map, TEMPSENSE0, &val);
-	if ((val & TEMPSENSE0_POWER_DOWN) == 0) {
 	/*
-		 * If a measurement is taking place, wait for a long enough
-		 * time for it to finish, and then check again.  If it still
-		 * does not finish, something must go wrong.
+	 * Need to disable thermal sensor, otherwise, when thermal core
+	 * try to get temperature before thermal sensor resume, a wrong
+	 * temperature will be read as the thermal sensor is powered
+	 * down.
 	 */
-		udelay(50);
-		regmap_read(map, TEMPSENSE0, &val);
-		if ((val & TEMPSENSE0_POWER_DOWN) == 0)
-			return -ETIMEDOUT;
-	}
+	regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_MEASURE_TEMP);
+	regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_POWER_DOWN);
+	data->mode = THERMAL_DEVICE_DISABLED;
 
 	return 0;
 }
 
 static int imx_thermal_resume(struct device *dev)
 {
-	/* Nothing to do for now */
+	struct imx_thermal_data *data = dev_get_drvdata(dev);
+	struct regmap *map = data->tempmon;
+
+	/* Enabled thermal sensor after resume */
+	regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_POWER_DOWN);
+	regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_MEASURE_TEMP);
+	data->mode = THERMAL_DEVICE_ENABLED;
+
 	return 0;
 }
 #endif