linux-kernel - [PATCH 4/7] ASoC: sun4i-i2s: Set sign extend sample

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Date:   Sat, 18 Apr 2020 16:39:20 +0200
From:   Clément Péron <peron.clem@...il.com>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>
Cc:     alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Marcus Cooper <codekipper@...il.com>,
        Clément Péron <peron.clem@...il.com>
Subject: [PATCH 4/7] ASoC: sun4i-i2s: Set sign extend sample

From: Marcus Cooper <codekipper@...il.com>

On the newer SoCs such as the H3 and A64 this is set by default
to transfer a 0 after each sample in each slot. However the A10
and A20 SoCs that this driver was developed on had a default
setting where it padded the audio gain with zeros.

This isn't a problem whilst we have only support for 16bit audio
but with larger sample resolution rates in the pipeline then SEXT
bits should be cleared so that they also pad at the LSB. Without
this the audio gets distorted.

Signed-off-by: Marcus Cooper <codekipper@...il.com>
Signed-off-by: Clément Péron <peron.clem@...il.com>
---
 sound/soc/sunxi/sun4i-i2s.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
index a23c9f2a3f8c..e5f00be8cdcf 100644
--- a/sound/soc/sunxi/sun4i-i2s.c
+++ b/sound/soc/sunxi/sun4i-i2s.c
@@ -663,6 +663,12 @@ static int sun4i_i2s_set_soc_fmt(const struct sun4i_i2s *i2s,
 	}
 	regmap_update_bits(i2s->regmap, SUN4I_I2S_CTRL_REG,
 			   SUN4I_I2S_CTRL_MODE_MASK, val);
+
+	/* Set sign extension to pad out LSB with 0 */
+	regmap_update_bits(i2s->regmap, SUN4I_I2S_FMT1_REG,
+			   SUN4I_I2S_FMT1_REG_SEXT_MASK,
+			   SUN4I_I2S_FMT1_REG_SEXT(0));
+
 	return 0;
 }
 
@@ -765,6 +771,11 @@ static int sun8i_i2s_set_soc_fmt(const struct sun4i_i2s *i2s,
 			   SUN8I_I2S_CTRL_BCLK_OUT | SUN8I_I2S_CTRL_LRCK_OUT,
 			   val);
 
+	/* Set sign extension to pad out LSB with 0 */
+	regmap_update_bits(i2s->regmap, SUN4I_I2S_FMT1_REG,
+			   SUN8I_I2S_FMT1_REG_SEXT_MASK,
+			   SUN8I_I2S_FMT1_REG_SEXT(0));
+
 	return 0;
 }
 
@@ -867,6 +878,11 @@ static int sun50i_i2s_set_soc_fmt(const struct sun4i_i2s *i2s,
 			   SUN8I_I2S_CTRL_BCLK_OUT | SUN8I_I2S_CTRL_LRCK_OUT,
 			   val);
 
+	/* Set sign extension to pad out LSB with 0 */
+	regmap_update_bits(i2s->regmap, SUN4I_I2S_FMT1_REG,
+			   SUN8I_I2S_FMT1_REG_SEXT_MASK,
+			   SUN8I_I2S_FMT1_REG_SEXT(0));
+
 	return 0;
 }
 
-- 
2.20.1