ASoC: tegra-alt: SLCG: Implement MBIST WAR for i2s

I2S MBIST comes up in random state and therefore
SLCG needs to be toggled OFF and ON before the I2S
controller can be used normally.

This patch implements WAR in response to SLCG notifier.

- Set I2S controller in master mode.
- toggled I2S SLCG OFF and ON.

Bug 200035860

Change-Id: I17b727034a33adf12f64eed0673665f26f4267c0
Signed-off-by: Dara Ramesh <dramesh@nvidia.com>
Reviewed-on: http://git-master/r/538402
Reviewed-by: Sumit Bhattacharya <sumitb@nvidia.com>
Reviewed-by: Prashant Gaikwad <pgaikwad@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User

sound/soc/tegra-alt/tegra210_i2s_alt.c

@@ -31,7 +31,9 @@
 #include <linux/pinctrl/consumer.h>
 #include <linux/regulator/consumer.h>
 #include <linux/of_device.h>
+#include <linux/delay.h>
 #include <linux/debugfs.h>
+#include <linux/tegra-powergate.h>
 
 #include "tegra210_xbar_alt.h"
 #include "tegra210_i2s_alt.h"
@@ -353,6 +355,35 @@ static int tegra210_i2s_codec_probe(struct snd_soc_codec *codec)
 	return 0;
 }
 
+static int _tegra210_i2s_slcg_notifier(struct notifier_block *nb,
+	unsigned long unused0, void *unused1)
+{
+	struct tegra210_i2s *i2s = container_of(nb, struct tegra210_i2s,
+								slgc_notifier);
+	unsigned int mask, val, i2s_ctrl;
+
+	/* Save the I2S CTRL before implement MBIST WAR */
+	regmap_read(i2s->regmap, TEGRA210_I2S_CTRL, &i2s_ctrl);
+
+	mask = TEGRA210_I2S_CTRL_MASTER_EN_MASK;
+	val = TEGRA210_I2S_CTRL_MASTER_EN;
+	/* Set I2S controller in master mode */
+	regmap_update_bits(i2s->regmap, TEGRA210_I2S_CTRL, mask, val);
+	/* Disable slcg, wait a while and re-enable it */
+	regmap_write(i2s->regmap, TEGRA210_I2S_CG, 0);
+	regmap_read(i2s->regmap, TEGRA210_I2S_CG, &val);
+
+	udelay(1);
+
+	regmap_write(i2s->regmap, TEGRA210_I2S_CG, 1);
+
+	/* Restore the I2S CTRL */
+	regmap_write(i2s->regmap, TEGRA210_I2S_CTRL, i2s_ctrl);
+
+	return NOTIFY_OK;
+}
+
+
 static struct snd_soc_dai_ops tegra210_i2s_dai_ops = {
 	.set_fmt	= tegra210_i2s_set_fmt,
 	.hw_params	= tegra210_i2s_hw_params,
@@ -641,6 +672,11 @@ static int tegra210_i2s_platform_probe(struct platform_device *pdev)
 		ret = PTR_ERR(i2s->regmap);
 		goto err_pll_a_out0_clk_put;
 	}
+
+	i2s->slgc_notifier.notifier_call = _tegra210_i2s_slcg_notifier;
+	slcg_register_notifier(TEGRA_POWERGATE_APE,
+		&i2s->slgc_notifier);
+
 	regcache_cache_only(i2s->regmap, true);
 
 	if (of_property_read_u32(np, "nvidia,ahub-i2s-id",