ASoC: SOF: PM: implement prepare/complete callbacks

Implement the prepare() and complete() callbacks for power management,
initialize s0_suspend flag at prepare(), and reset it at complete().
Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20191025224122.7718-22-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/pm.c

@@ -439,3 +439,26 @@ int snd_sof_suspend(struct device *dev)
 	return sof_suspend(dev, false);
 }
 EXPORT_SYMBOL(snd_sof_suspend);
+
+int snd_sof_prepare(struct device *dev)
+{
+	struct snd_sof_dev *sdev = dev_get_drvdata(dev);
+
+#if defined(CONFIG_ACPI)
+	sdev->s0_suspend = acpi_target_system_state() == ACPI_STATE_S0;
+#else
+	/* will suspend to S3 by default */
+	sdev->s0_suspend = false;
+#endif
+
+	return 0;
+}
+EXPORT_SYMBOL(snd_sof_prepare);
+
+void snd_sof_complete(struct device *dev)
+{
+	struct snd_sof_dev *sdev = dev_get_drvdata(dev);
+
+	sdev->s0_suspend = false;
+}
+EXPORT_SYMBOL(snd_sof_complete);

sound/soc/sof/sof-priv.h

@@ -492,6 +492,8 @@ int snd_sof_runtime_resume(struct device *dev);
 int snd_sof_runtime_idle(struct device *dev);
 int snd_sof_resume(struct device *dev);
 int snd_sof_suspend(struct device *dev);
+int snd_sof_prepare(struct device *dev);
+void snd_sof_complete(struct device *dev);
 int snd_sof_set_d0_substate(struct snd_sof_dev *sdev,
 			    enum sof_d0_substate d0_substate);