ASoC: tegra20: spdif: Reset hardware

Reset S/PDIF controller on runtime PM suspend/resume to ensure that we
always have a consistent hardware state.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20211204143725.31646-11-digetx@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/tegra/tegra20_spdif.c

@@ -7,6 +7,7 @@
  */
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/io.h>
 #include <linux/module.h>
@@ -14,6 +15,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/regmap.h>
+#include <linux/reset.h>
 #include <linux/slab.h>
 #include <sound/core.h>
 #include <sound/pcm.h>
@@ -27,6 +29,8 @@ static __maybe_unused int tegra20_spdif_runtime_suspend(struct device *dev)
 {
 	struct tegra20_spdif *spdif = dev_get_drvdata(dev);
 
+	regcache_cache_only(spdif->regmap, true);
+
 	clk_disable_unprepare(spdif->clk_spdif_out);
 
 	return 0;
@@ -37,13 +41,35 @@ static __maybe_unused int tegra20_spdif_runtime_resume(struct device *dev)
 	struct tegra20_spdif *spdif = dev_get_drvdata(dev);
 	int ret;
 
+	ret = reset_control_assert(spdif->reset);
+	if (ret)
+		return ret;
+
 	ret = clk_prepare_enable(spdif->clk_spdif_out);
 	if (ret) {
 		dev_err(dev, "clk_enable failed: %d\n", ret);
 		return ret;
 	}
 
+	usleep_range(10, 100);
+
+	ret = reset_control_deassert(spdif->reset);
+	if (ret)
+		goto disable_clocks;
+
+	regcache_cache_only(spdif->regmap, false);
+	regcache_mark_dirty(spdif->regmap);
+
+	ret = regcache_sync(spdif->regmap);
+	if (ret)
+		goto disable_clocks;
+
 	return 0;
+
+disable_clocks:
+	clk_disable_unprepare(spdif->clk_spdif_out);
+
+	return ret;
 }
 
 static int tegra20_spdif_hw_params(struct snd_pcm_substream *substream,
@@ -268,6 +294,12 @@ static int tegra20_spdif_platform_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(&pdev->dev, spdif);
 
+	spdif->reset = devm_reset_control_get_exclusive(&pdev->dev, NULL);
+	if (IS_ERR(spdif->reset)) {
+		dev_err(&pdev->dev, "Can't retrieve spdif reset\n");
+		return PTR_ERR(spdif->reset);
+	}
+
 	spdif->clk_spdif_out = devm_clk_get(&pdev->dev, "out");
 	if (IS_ERR(spdif->clk_spdif_out)) {
 		dev_err(&pdev->dev, "Could not retrieve spdif clock\n");

sound/soc/tegra/tegra20_spdif.h

@@ -451,6 +451,7 @@ struct tegra20_spdif {
 	struct snd_dmaengine_dai_dma_data capture_dma_data;
 	struct snd_dmaengine_dai_dma_data playback_dma_data;
 	struct regmap *regmap;
+	struct reset_control *reset;
 };
 
 #endif