iio: light: rpr0521 on-off sequence change for CONFIG_PM

Refactor _set_power_state(), _resume() and _suspend().
Enable measurement only when needed, not in _init(). System can suspend
during measurement and measurement is continued on resume.
Pm turns off measurement when both ps and als measurements are disabled for
2 seconds. During off-time the power save is 20-500mA, typically 180mA.

Signed-off-by: Mikko Koivunen <mikko.koivunen@fi.rohmeurope.com>
Acked-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/light/rpr0521.c

@@ -9,7 +9,7 @@
  *
  * IIO driver for RPR-0521RS (7-bit I2C slave address 0x38).
  *
- * TODO: illuminance channel, PM support, buffer
+ * TODO: illuminance channel, buffer
  */
 
 #include <linux/module.h>
@@ -142,9 +142,11 @@ struct rpr0521_data {
 	bool als_dev_en;
 	bool pxs_dev_en;
 
-	/* optimize runtime pm ops - enable device only if needed */
+	/* optimize runtime pm ops - enable/disable device only if needed */
 	bool als_ps_need_en;
 	bool pxs_ps_need_en;
+	bool als_need_dis;
+	bool pxs_need_dis;
 
 	struct regmap *regmap;
 };
@@ -230,40 +232,32 @@ static int rpr0521_pxs_enable(struct rpr0521_data *data, u8 status)
  * @on: state to be set for devices in @device_mask
  * @device_mask: bitmask specifying for which device we need to update @on state
  *
- * We rely on rpr0521_runtime_resume to enable our @device_mask devices, but
- * if (for example) PXS was enabled (pxs_dev_en = true) by a previous call to
- * rpr0521_runtime_resume and we want to enable ALS we MUST set ALS enable
- * bit of RPR0521_REG_MODE_CTRL here because rpr0521_runtime_resume will not
- * be called twice.
+ * Calls for this function must be balanced so that each ON should have matching
+ * OFF. Otherwise pm usage_count gets out of sync.
  */
 static int rpr0521_set_power_state(struct rpr0521_data *data, bool on,
 				   u8 device_mask)
 {
 #ifdef CONFIG_PM
 	int ret;
-	u8 update_mask = 0;
 
 	if (device_mask & RPR0521_MODE_ALS_MASK) {
-		if (on && !data->als_ps_need_en && data->pxs_dev_en)
-			update_mask |= RPR0521_MODE_ALS_MASK;
-		else
-			data->als_ps_need_en = on;
+		data->als_ps_need_en = on;
+		data->als_need_dis = !on;
 	}
 
 	if (device_mask & RPR0521_MODE_PXS_MASK) {
-		if (on && !data->pxs_ps_need_en && data->als_dev_en)
-			update_mask |= RPR0521_MODE_PXS_MASK;
-		else
-			data->pxs_ps_need_en = on;
-	}
-
-	if (update_mask) {
-		ret = regmap_update_bits(data->regmap, RPR0521_REG_MODE_CTRL,
-					 update_mask, update_mask);
-		if (ret < 0)
-			return ret;
+		data->pxs_ps_need_en = on;
+		data->pxs_need_dis = !on;
 	}
 
+	/*
+	 * On: _resume() is called only when we are suspended
+	 * Off: _suspend() is called after delay if _resume() is not
+	 * called before that.
+	 * Note: If either measurement is re-enabled before _suspend(),
+	 * both stay enabled until _suspend().
+	 */
 	if (on) {
 		ret = pm_runtime_get_sync(&data->client->dev);
 	} else {
@@ -279,6 +273,23 @@ static int rpr0521_set_power_state(struct rpr0521_data *data, bool on,
 
 		return ret;
 	}
+
+	if (on) {
+		/* If _resume() was not called, enable measurement now. */
+		if (data->als_ps_need_en) {
+			ret = rpr0521_als_enable(data, RPR0521_MODE_ALS_ENABLE);
+			if (ret)
+				return ret;
+			data->als_ps_need_en = false;
+		}
+
+		if (data->pxs_ps_need_en) {
+			ret = rpr0521_pxs_enable(data, RPR0521_MODE_PXS_ENABLE);
+			if (ret)
+				return ret;
+			data->pxs_ps_need_en = false;
+		}
+	}
 #endif
 	return 0;
 }
@@ -425,12 +436,14 @@ static int rpr0521_init(struct rpr0521_data *data)
 		return ret;
 	}
 
+#ifndef CONFIG_PM
 	ret = rpr0521_als_enable(data, RPR0521_MODE_ALS_ENABLE);
 	if (ret < 0)
 		return ret;
 	ret = rpr0521_pxs_enable(data, RPR0521_MODE_PXS_ENABLE);
 	if (ret < 0)
 		return ret;
+#endif
 
 	return 0;
 }
@@ -560,9 +573,16 @@ static int rpr0521_runtime_suspend(struct device *dev)
 	struct rpr0521_data *data = iio_priv(indio_dev);
 	int ret;
 
-	/* disable channels and sets {als,pxs}_dev_en to false */
 	mutex_lock(&data->lock);
+	/* If measurements are enabled, enable them on resume */
+	if (!data->als_need_dis)
+		data->als_ps_need_en = data->als_dev_en;
+	if (!data->pxs_need_dis)
+		data->pxs_ps_need_en = data->pxs_dev_en;
+
+	/* disable channels and sets {als,pxs}_dev_en to false */
 	ret = rpr0521_poweroff(data);
+	regcache_mark_dirty(data->regmap);
 	mutex_unlock(&data->lock);
 
 	return ret;
@@ -574,6 +594,7 @@ static int rpr0521_runtime_resume(struct device *dev)
 	struct rpr0521_data *data = iio_priv(indio_dev);
 	int ret;
 
+	regcache_sync(data->regmap);
 	if (data->als_ps_need_en) {
 		ret = rpr0521_als_enable(data, RPR0521_MODE_ALS_ENABLE);
 		if (ret < 0)
@@ -587,6 +608,7 @@ static int rpr0521_runtime_resume(struct device *dev)
 			return ret;
 		data->pxs_ps_need_en = false;
 	}
+	msleep(100);	//wait for first measurement result
 
 	return 0;
 }