[alsa-devel] [PATCH 13/21] ASoC: sun4i-i2s: Fix the LRCK polarity

[Maxime Ripard]

From: Maxime Ripard <maxime.ripard at bootlin.com>

The LRCK polarity "normal" polarity in the I2S/TDM specs and in the
Allwinner datasheet are not the same. In the case where the i2s controller
is being used as the LRCK master, it's pretty clear when looked at under a
scope.

Let's fix this, and add a comment to clear up as much the confusion as
possible.

Fixes: 7d2993811a1e ("ASoC: sun4i-i2s: Add support for H3")
Fixes: 21faaea1343f ("ASoC: sun4i-i2s: Add support for A83T")
Signed-off-by: Maxime Ripard <maxime.ripard at bootlin.com>
---
 sound/soc/sunxi/sun4i-i2s.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
index e614c2d52af5..9c9061621b15 100644
--- a/sound/soc/sunxi/sun4i-i2s.c
+++ b/sound/soc/sunxi/sun4i-i2s.c
@@ -570,23 +570,29 @@ static int sun8i_i2s_set_soc_fmt(const struct sun4i_i2s *i2s,
 	u32 mode, val;
 	u8 offset;
 
-	/* DAI clock polarity */
+	/*
+	 * DAI clock polarity
+	 *
+	 * The setup for LRCK contradicts the datasheet, but under a
+	 * scope it's clear that the LRCK polarity is reversed
+	 * compared to the expected polarity on the bus.
+	 */
 	switch (fmt & SND_SOC_DAIFMT_INV_MASK) {
 	case SND_SOC_DAIFMT_IB_IF:
 		/* Invert both clocks */
-		val = SUN8I_I2S_FMT0_BCLK_POLARITY_INVERTED |
-		      SUN8I_I2S_FMT0_LRCLK_POLARITY_INVERTED;
+		val = SUN8I_I2S_FMT0_BCLK_POLARITY_INVERTED;
 		break;
 	case SND_SOC_DAIFMT_IB_NF:
 		/* Invert bit clock */
-		val = SUN8I_I2S_FMT0_BCLK_POLARITY_INVERTED;
+		val = SUN8I_I2S_FMT0_BCLK_POLARITY_INVERTED |
+		      SUN8I_I2S_FMT0_LRCLK_POLARITY_INVERTED;
 		break;
 	case SND_SOC_DAIFMT_NB_IF:
 		/* Invert frame clock */
-		val = SUN8I_I2S_FMT0_LRCLK_POLARITY_INVERTED;
+		val = 0;
 		break;
 	case SND_SOC_DAIFMT_NB_NF:
-		val = 0;
+		val = SUN8I_I2S_FMT0_LRCLK_POLARITY_INVERTED;
 		break;
 	default:
 		return -EINVAL;
-- 
git-series 0.9.1