[PATCH v2 8/9] spi: prepare runtime PM support for SPI devices

[Mika Westerberg <mika.westerberg@linux.intel.com>]

This patch adds runtime PM support for the SPI bus analogous to what has
been done for the I2C bus. This means that the SPI core prepares runtime PM
for a client device just before a driver is about to be bound to it.
Devices that are not bound to any driver are not prepared for runtime PM.

In order to participate the runtime PM of the SPI bus a device driver needs
to drop the device runtime PM reference count by calling pm_runtime_put()
in its ->probe() callback and possibly implement rest of the runtime PM
callbacks.

If the driver doesn't support runtime PM, the device in question is
regarded as being runtime PM active and powered on.

This patch adds also runtime PM support for the SPI master device because
it is needed to be able to runtime power manage the SPI controller device.
The SPI master device is handled along with the SPI controller device.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/spi/spi.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 978dda2..94ebab9 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -240,22 +240,61 @@ EXPORT_SYMBOL_GPL(spi_bus_type);
 static int spi_drv_probe(struct device *dev)
 {
 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
+	struct spi_device		*spi = to_spi_device(dev);
+	int				ret;
 
-	return sdrv->probe(to_spi_device(dev));
+	/* Make sure that the master is powered on */
+	pm_runtime_get_sync(&spi->master->dev);
+
+	/*
+	 * Enable runtime PM for the SPI device. The SPI device driver can
+	 * participate in runtime PM by calling pm_runtime_put() in its
+	 * probe() callback.
+	 */
+	pm_runtime_get_noresume(&spi->dev);
+	pm_runtime_set_active(&spi->dev);
+	pm_runtime_enable(&spi->dev);
+
+	ret = sdrv->probe(spi);
+	if (ret) {
+		pm_runtime_disable(&spi->dev);
+		pm_runtime_set_suspended(&spi->dev);
+		pm_runtime_put_noidle(&spi->dev);
+	}
+
+	pm_runtime_put(&spi->master->dev);
+
+	return ret;
 }
 
 static int spi_drv_remove(struct device *dev)
 {
 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
+	struct spi_device		*spi = to_spi_device(dev);
+	int				ret;
+
+	pm_runtime_get_sync(&spi->master->dev);
+
+	ret = sdrv->remove(spi);
+
+	/* Undo the runtime PM done in spi_drv_probe() */
+	pm_runtime_disable(&spi->dev);
+	pm_runtime_set_suspended(&spi->dev);
+	pm_runtime_put_noidle(&spi->dev);
 
-	return sdrv->remove(to_spi_device(dev));
+	pm_runtime_put(&spi->master->dev);
+
+	return ret;
 }
 
 static void spi_drv_shutdown(struct device *dev)
 {
 	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
+	struct spi_device		*spi = to_spi_device(dev);
 
+	pm_runtime_get_sync(&spi->master->dev);
 	sdrv->shutdown(to_spi_device(dev));
+	pm_runtime_put(&spi->master->dev);
 }
 
 /**
@@ -1174,6 +1213,10 @@ int spi_register_master(struct spi_master *master)
 		}
 	}
 
+	pm_runtime_set_active(&master->dev);
+	pm_runtime_no_callbacks(&master->dev);
+	pm_runtime_enable(&master->dev);
+
 	mutex_lock(&board_lock);
 	list_add_tail(&master->list, &spi_master_list);
 	list_for_each_entry(bi, &board_list, list)
@@ -1217,6 +1260,8 @@ void spi_unregister_master(struct spi_master *master)
 	list_del(&master->list);
 	mutex_unlock(&board_lock);
 
+	pm_runtime_disable(&master->dev);
+
 	dummy = device_for_each_child(&master->dev, NULL, __unregister);
 	device_unregister(&master->dev);
 }
-- 
1.8.4.rc3