iio: accel: kxsd9: Deploy system and runtime PM

This deploys runtime and system PM in the KXSD9 driver:

- Use the force_runtime_suspend/resume callbacks as system PM
  operations.

- Add buffer prepare/unprepare callbacks to grab the runtime
  PM while we're using buffered reads and put get/put_autosuspend
  in these.

- Insert get/put_autosuspend calls anywhere the IO is used from
  the raw read/write callbacks.

- Move the fullscale setting to be cached in the state container
  so we can restore it properly when coming back from
  system/runtime suspend.

- Set the autosuspend delay to two orders of magnitude that of
  the sensor start-up time (20ms) so we will autosuspend after
  2s.

- Register the callbacks in both the SPI and I2C subdrivers.

Tested with the I2C KXSD9 on the Qualcomm APQ8060 Dragonboard.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/accel/kxsd9-i2c.c

@@ -55,6 +55,7 @@ static struct i2c_driver kxsd9_i2c_driver = {
 	.driver = {
 		.name	= "kxsd9",
 		.of_match_table = of_match_ptr(kxsd9_of_match),
+		.pm = &kxsd9_dev_pm_ops,
 	},
 	.probe		= kxsd9_i2c_probe,
 	.remove		= kxsd9_i2c_remove,

drivers/iio/accel/kxsd9-spi.c

@@ -43,6 +43,7 @@ MODULE_DEVICE_TABLE(spi, kxsd9_spi_id);
 static struct spi_driver kxsd9_spi_driver = {
 	.driver = {
 		.name = "kxsd9",
+		.pm = &kxsd9_dev_pm_ops,
 	},
 	.probe = kxsd9_spi_probe,
 	.remove = kxsd9_spi_remove,

drivers/iio/accel/kxsd9.c

@@ -23,6 +23,7 @@
 #include <linux/bitops.h>
 #include <linux/delay.h>
 #include <linux/regulator/consumer.h>
+#include <linux/pm_runtime.h>
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 #include <linux/iio/buffer.h>
@@ -68,11 +69,13 @@
  * @dev: pointer to the parent device
  * @map: regmap to the device
  * @regs: regulators for this device, VDD and IOVDD
+ * @scale: the current scaling setting
  */
 struct kxsd9_state {
 	struct device *dev;
 	struct regmap *map;
 	struct regulator_bulk_data regs[2];
+	u8 scale;
 };
 
 #define KXSD9_SCALE_2G "0.011978"
@@ -111,6 +114,10 @@ static int kxsd9_write_scale(struct iio_dev *indio_dev, int micro)
 				 i);
 	if (ret < 0)
 		goto error_ret;
+
+	/* Cached scale when the sensor is powered down */
+	st->scale = i;
+
 error_ret:
 	return ret;
 }
@@ -133,6 +140,9 @@ static int kxsd9_write_raw(struct iio_dev *indio_dev,
 			   long mask)
 {
 	int ret = -EINVAL;
+	struct kxsd9_state *st = iio_priv(indio_dev);
+
+	pm_runtime_get_sync(st->dev);
 
 	if (mask == IIO_CHAN_INFO_SCALE) {
 		/* Check no integer component */
@@ -141,6 +151,9 @@ static int kxsd9_write_raw(struct iio_dev *indio_dev,
 		ret = kxsd9_write_scale(indio_dev, val2);
 	}
 
+	pm_runtime_mark_last_busy(st->dev);
+	pm_runtime_put_autosuspend(st->dev);
+
 	return ret;
 }
 
@@ -154,6 +167,8 @@ static int kxsd9_read_raw(struct iio_dev *indio_dev,
 	__be16 raw_val;
 	u16 nval;
 
+	pm_runtime_get_sync(st->dev);
+
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		ret = regmap_bulk_read(st->map, chan->address, &raw_val,
@@ -184,6 +199,9 @@ static int kxsd9_read_raw(struct iio_dev *indio_dev,
 	}
 
 error_ret:
+	pm_runtime_mark_last_busy(st->dev);
+	pm_runtime_put_autosuspend(st->dev);
+
 	return ret;
 };
 
@@ -214,6 +232,32 @@ static irqreturn_t kxsd9_trigger_handler(int irq, void *p)
 	return IRQ_HANDLED;
 }
 
+static int kxsd9_buffer_preenable(struct iio_dev *indio_dev)
+{
+	struct kxsd9_state *st = iio_priv(indio_dev);
+
+	pm_runtime_get_sync(st->dev);
+
+	return 0;
+}
+
+static int kxsd9_buffer_postdisable(struct iio_dev *indio_dev)
+{
+	struct kxsd9_state *st = iio_priv(indio_dev);
+
+	pm_runtime_mark_last_busy(st->dev);
+	pm_runtime_put_autosuspend(st->dev);
+
+	return 0;
+}
+
+static const struct iio_buffer_setup_ops kxsd9_buffer_setup_ops = {
+	.preenable = kxsd9_buffer_preenable,
+	.postenable = iio_triggered_buffer_postenable,
+	.predisable = iio_triggered_buffer_predisable,
+	.postdisable = kxsd9_buffer_postdisable,
+};
+
 #define KXSD9_ACCEL_CHAN(axis, index)						\
 	{								\
 		.type = IIO_ACCEL,					\
@@ -285,7 +329,7 @@ static int kxsd9_power_up(struct kxsd9_state *st)
 			   KXSD9_CTRL_C_LP_1000HZ |
 			   KXSD9_CTRL_C_MOT_LEV	|
 			   KXSD9_CTRL_C_MOT_LAT |
-			   KXSD9_CTRL_C_FS_2G);
+			   st->scale);
 	if (ret)
 		return ret;
 
@@ -369,13 +413,15 @@ int kxsd9_common_probe(struct device *dev,
 		dev_err(dev, "Cannot get regulators\n");
 		return ret;
 	}
+	/* Default scaling */
+	st->scale = KXSD9_CTRL_C_FS_2G;
 
 	kxsd9_power_up(st);
 
 	ret = iio_triggered_buffer_setup(indio_dev,
 					 iio_pollfunc_store_time,
 					 kxsd9_trigger_handler,
-					 NULL);
+					 &kxsd9_buffer_setup_ops);
 	if (ret) {
 		dev_err(dev, "triggered buffer setup failed\n");
 		goto err_power_down;
@@ -387,6 +433,19 @@ int kxsd9_common_probe(struct device *dev,
 
 	dev_set_drvdata(dev, indio_dev);
 
+	/* Enable runtime PM */
+	pm_runtime_get_noresume(dev);
+	pm_runtime_set_active(dev);
+	pm_runtime_enable(dev);
+	/*
+	 * Set autosuspend to two orders of magnitude larger than the
+	 * start-up time. 20ms start-up time means 2000ms autosuspend,
+	 * i.e. 2 seconds.
+	 */
+	pm_runtime_set_autosuspend_delay(dev, 2000);
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_put(dev);
+
 	return 0;
 
 err_cleanup_buffer:
@@ -405,12 +464,41 @@ int kxsd9_common_remove(struct device *dev)
 
 	iio_triggered_buffer_cleanup(indio_dev);
 	iio_device_unregister(indio_dev);
+	pm_runtime_get_sync(dev);
+	pm_runtime_put_noidle(dev);
+	pm_runtime_disable(dev);
 	kxsd9_power_down(st);
 
 	return 0;
 }
 EXPORT_SYMBOL(kxsd9_common_remove);
 
+#ifdef CONFIG_PM
+static int kxsd9_runtime_suspend(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct kxsd9_state *st = iio_priv(indio_dev);
+
+	return kxsd9_power_down(st);
+}
+
+static int kxsd9_runtime_resume(struct device *dev)
+{
+	struct iio_dev *indio_dev = dev_get_drvdata(dev);
+	struct kxsd9_state *st = iio_priv(indio_dev);
+
+	return kxsd9_power_up(st);
+}
+#endif /* CONFIG_PM */
+
+const struct dev_pm_ops kxsd9_dev_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+	SET_RUNTIME_PM_OPS(kxsd9_runtime_suspend,
+			   kxsd9_runtime_resume, NULL)
+};
+EXPORT_SYMBOL(kxsd9_dev_pm_ops);
+
 MODULE_AUTHOR("Jonathan Cameron <jic23@kernel.org>");
 MODULE_DESCRIPTION("Kionix KXSD9 driver");
 MODULE_LICENSE("GPL v2");

drivers/iio/accel/kxsd9.h

@@ -8,3 +8,5 @@ int kxsd9_common_probe(struct device *dev,
 		       struct regmap *map,
 		       const char *name);
 int kxsd9_common_remove(struct device *dev);
+
+extern const struct dev_pm_ops kxsd9_dev_pm_ops;