ASoC: img-spdif-in: Add suspend / resume handling

Implement suspend and resume callbacks to save and restore register
state, to support platforms where the power is disabled during suspend.

In future the driver could be converted to use regmap which would
simplify the suspend and resume code.
Signed-off-by: Ed Blake <ed.blake@sondrel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/img/img-spdif-in.c

@@ -82,6 +82,8 @@ struct img_spdif_in {
 	unsigned int single_freq;
 	unsigned int multi_freqs[IMG_SPDIF_IN_NUM_ACLKGEN];
 	bool active;
+	u32 suspend_clkgen;
+	u32 suspend_ctl;
 
 	/* Write-only registers */
 	unsigned int aclkgen_regs[IMG_SPDIF_IN_NUM_ACLKGEN];
@@ -785,16 +787,51 @@ static int img_spdif_in_dev_remove(struct platform_device *pdev)
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int img_spdif_in_suspend(struct device *dev)
+{
+	struct img_spdif_in *spdif = dev_get_drvdata(dev);
+
+	spdif->suspend_clkgen = img_spdif_in_readl(spdif, IMG_SPDIF_IN_CLKGEN);
+	spdif->suspend_ctl = img_spdif_in_readl(spdif, IMG_SPDIF_IN_CTL);
+
+	clk_disable_unprepare(spdif->clk_sys);
+
+	return 0;
+}
+
+static int img_spdif_in_resume(struct device *dev)
+{
+	struct img_spdif_in *spdif = dev_get_drvdata(dev);
+	int i;
+
+	clk_prepare_enable(spdif->clk_sys);
+
+	for (i = 0; i < IMG_SPDIF_IN_NUM_ACLKGEN; i++)
+		img_spdif_in_aclkgen_writel(spdif, i);
+
+	img_spdif_in_writel(spdif, spdif->suspend_clkgen, IMG_SPDIF_IN_CLKGEN);
+	img_spdif_in_writel(spdif, spdif->suspend_ctl, IMG_SPDIF_IN_CTL);
+
+	return 0;
+}
+#endif
+
 static const struct of_device_id img_spdif_in_of_match[] = {
 	{ .compatible = "img,spdif-in" },
 	{}
 };
 MODULE_DEVICE_TABLE(of, img_spdif_in_of_match);
 
+static const struct dev_pm_ops img_spdif_in_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(img_spdif_in_suspend, img_spdif_in_resume)
+};
+
 static struct platform_driver img_spdif_in_driver = {
 	.driver = {
 		.name = "img-spdif-in",
-		.of_match_table = img_spdif_in_of_match
+		.of_match_table = img_spdif_in_of_match,
+		.pm = &img_spdif_in_pm_ops
 	},
 	.probe = img_spdif_in_probe,
 	.remove = img_spdif_in_dev_remove