pwm: lpss: Add support for runtime PM

To be able to save some power when PWM is not in use, add support for
runtime PM for this driver. This also allows the platform to transition to
low power S0ix states when the system is idle.

Signed-off-by: Huiquan Zhong <huiquan.zhong@intel.com>
Signed-off-by: Qipeng Zha <qipeng.zha@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
diff --git a/drivers/pwm/pwm-lpss-platform.c b/drivers/pwm/pwm-lpss-platform.c
index a914aac..54433fc 100644
--- a/drivers/pwm/pwm-lpss-platform.c
+++ b/drivers/pwm/pwm-lpss-platform.c
@@ -14,6 +14,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 
 #include "pwm-lpss.h"
 
@@ -36,6 +37,10 @@
 		return PTR_ERR(lpwm);
 
 	platform_set_drvdata(pdev, lpwm);
+
+	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
 	return 0;
 }
 
@@ -43,6 +48,7 @@
 {
 	struct pwm_lpss_chip *lpwm = platform_get_drvdata(pdev);
 
+	pm_runtime_disable(&pdev->dev);
 	return pwm_lpss_remove(lpwm);
 }