spi: dw: Add basic runtime PM support

Enable runtime PM so that the clock used to access the registers in the
peripheral is turned on using a clock domain.
Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Gareth Williams <gareth.williams.jx@renesas.com>
Link: https://lore.kernel.org/r/1568793876-9009-4-git-send-email-gareth.williams.jx@renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-dw.c

@@ -10,6 +10,7 @@
 #include <linux/module.h>
 #include <linux/highmem.h>
 #include <linux/delay.h>
+#include <linux/pm_runtime.h>
 #include <linux/slab.h>
 #include <linux/spi/spi.h>
 
@@ -493,10 +494,13 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
 	master->dev.of_node = dev->of_node;
 	master->dev.fwnode = dev->fwnode;
 	master->flags = SPI_MASTER_GPIO_SS;
+	master->auto_runtime_pm = true;
 
 	if (dws->set_cs)
 		master->set_cs = dws->set_cs;
 
+	pm_runtime_enable(dev);
+
 	/* Basic HW init */
 	spi_hw_init(dev, dws);
 
@@ -525,6 +529,7 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
 	spi_enable_chip(dws, 0);
 	free_irq(dws->irq, master);
 err_free_master:
+	pm_runtime_disable(dev);
 	spi_controller_put(master);
 	return ret;
 }
@@ -539,6 +544,9 @@ void dw_spi_remove_host(struct dw_spi *dws)
 
 	spi_shutdown_chip(dws);
 
+	if (dws->master)
+		pm_runtime_disable(&dws->master->dev);
+
 	free_irq(dws->irq, dws->master);
 }
 EXPORT_SYMBOL_GPL(dw_spi_remove_host);