ASoC: tegra: implement suspend/resume for Tegra30 I2S

Add tegra30_i2s_{suspend,resume}. These use regcache functions to
restore all HW registers after power loss during a suspend/resume cycle.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

sound/soc/tegra/tegra30_i2s.c

@@ -514,6 +514,24 @@ static int tegra30_i2s_platform_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int tegra30_i2s_suspend(struct device *dev)
+{
+	struct tegra30_i2s *i2s = dev_get_drvdata(dev);
+
+	regcache_mark_dirty(i2s->regmap);
+
+	return 0;
+}
+
+static int tegra30_i2s_resume(struct device *dev)
+{
+	struct tegra30_i2s *i2s = dev_get_drvdata(dev);
+
+	return regcache_sync(i2s->regmap);
+}
+#endif
+
 static const struct of_device_id tegra30_i2s_of_match[] = {
 	{ .compatible = "nvidia,tegra30-i2s", },
 	{},
@@ -522,6 +540,7 @@ static const struct of_device_id tegra30_i2s_of_match[] = {
 static const struct dev_pm_ops tegra30_i2s_pm_ops = {
 	SET_RUNTIME_PM_OPS(tegra30_i2s_runtime_suspend,
 			   tegra30_i2s_runtime_resume, NULL)
+	SET_SYSTEM_SLEEP_PM_OPS(tegra30_i2s_suspend, tegra30_i2s_resume)
 };
 
 static struct platform_driver tegra30_i2s_driver = {