[PATCH 3/3] ASoC: cs4271: Add support for the external mclk

[Herve Codina <herve.codina@bootlin.com>]

The mclk (master clock) of the cs4271 codec can be an input clock.

In this case the connected clock needs to be enabled outside of any
audio stream. Indeed, this clock is needed for i2c communication.

Add support of this clock and enable it before the first i2c transfer.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 sound/soc/codecs/cs4271.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/sound/soc/codecs/cs4271.c b/sound/soc/codecs/cs4271.c
index ff9c6628224c..481a2c20b7cf 100644
--- a/sound/soc/codecs/cs4271.c
+++ b/sound/soc/codecs/cs4271.c
@@ -10,6 +10,7 @@
  * DAPM support not implemented.
  */
 
+#include <linux/clk.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
@@ -163,6 +164,7 @@ struct cs4271_private {
 	/* enable soft reset workaround */
 	bool				enable_soft_reset;
 	struct regulator_bulk_data      supplies[ARRAY_SIZE(supply_names)];
+	struct clk *clk;
 };
 
 static const struct snd_soc_dapm_widget cs4271_dapm_widgets[] = {
@@ -567,22 +569,36 @@ static int cs4271_component_probe(struct snd_soc_component *component)
 		cs4271->enable_soft_reset = cs4271plat->enable_soft_reset;
 	}
 
+	ret = clk_prepare_enable(cs4271->clk);
+	if (ret) {
+		dev_err(component->dev, "Failed to enable clk: %d\n", ret);
+		goto err_disable_regulators;
+	}
+
+	/*
+	 * Be sure to have the clock and power-supplies stable before releasing
+	 * the reset.
+	 */
+	fsleep(1000);
+
 	/* Reset codec */
 	cs4271_reset(component);
 
 	ret = regcache_sync(cs4271->regmap);
 	if (ret < 0)
-		return ret;
+		goto err_force_reset;
 
 	ret = regmap_update_bits(cs4271->regmap, CS4271_MODE2,
 				 CS4271_MODE2_PDN | CS4271_MODE2_CPEN,
 				 CS4271_MODE2_PDN | CS4271_MODE2_CPEN);
 	if (ret < 0)
-		return ret;
+		goto err_force_reset;
+
 	ret = regmap_update_bits(cs4271->regmap, CS4271_MODE2,
 				 CS4271_MODE2_PDN, 0);
 	if (ret < 0)
-		return ret;
+		goto err_force_reset;
+
 	/* Power-up sequence requires 85 uS */
 	udelay(85);
 
@@ -592,6 +608,13 @@ static int cs4271_component_probe(struct snd_soc_component *component)
 				   CS4271_MODE2_MUTECAEQUB);
 
 	return 0;
+
+err_force_reset:
+	gpiod_set_value(cs4271->reset, 1);
+	clk_disable_unprepare(cs4271->clk);
+err_disable_regulators:
+	regulator_bulk_disable(ARRAY_SIZE(cs4271->supplies), cs4271->supplies);
+	return ret;
 }
 
 static void cs4271_component_remove(struct snd_soc_component *component)
@@ -603,6 +626,7 @@ static void cs4271_component_remove(struct snd_soc_component *component)
 
 	regcache_mark_dirty(cs4271->regmap);
 	regulator_bulk_disable(ARRAY_SIZE(cs4271->supplies), cs4271->supplies);
+	clk_disable_unprepare(cs4271->clk);
 };
 
 static const struct snd_soc_component_driver soc_component_dev_cs4271 = {
@@ -637,6 +661,10 @@ static int cs4271_common_probe(struct device *dev,
 				     "error retrieving RESET GPIO\n");
 	gpiod_set_consumer_name(cs4271->reset, "CS4271 Reset");
 
+	cs4271->clk = devm_clk_get_optional(dev, "mclk");
+	if (IS_ERR(cs4271->clk))
+		return dev_err_probe(dev, PTR_ERR(cs4271->clk), "Failed to get mclk\n");
+
 	for (i = 0; i < ARRAY_SIZE(supply_names); i++)
 		cs4271->supplies[i].supply = supply_names[i];
 
-- 
2.51.0