[PATCH v2] ASoC: sun8i-codec: Set the BCLK divider

[Maxime Ripard]

While the current code was reporting to be able to work in master mode, it
failed to do so because the BCLK divider wasn't programmed, meaning that
the BCLK would run at the PLL's frequency no matter the sample rate.

It was obviously a bit too fast.

Add support to retrieve the divider to use, and set it. Since our PLL is
not always able to generate a perfect multiple of the sample rate, we'll
have to choose the closest divider that matches our setup.

Fixes: 36c684936fae ("ASoC: Add sun8i digital audio codec")
Cc: <stable at vger.kernel.org>
Reviewed-by: Chen-Yu Tsai <wens at csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com>

---
Changes from v1:
  - Hardcoded the bit width to remain consistent with the rest of the driver
---
 sound/soc/sunxi/sun8i-codec.c | 51 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/sound/soc/sunxi/sun8i-codec.c b/sound/soc/sunxi/sun8i-codec.c
index c2ceca485d6a..7a312168f864 100644
--- a/sound/soc/sunxi/sun8i-codec.c
+++ b/sound/soc/sunxi/sun8i-codec.c
@@ -73,6 +73,7 @@
 #define SUN8I_SYS_SR_CTRL_AIF2_FS_MASK		GENMASK(11, 8)
 #define SUN8I_AIF1CLK_CTRL_AIF1_WORD_SIZ_MASK	GENMASK(5, 4)
 #define SUN8I_AIF1CLK_CTRL_AIF1_LRCK_DIV_MASK	GENMASK(8, 6)
+#define SUN8I_AIF1CLK_CTRL_AIF1_BCLK_DIV_MASK	GENMASK(12, 9)
 
 struct sun8i_codec {
 	struct device	*dev;
@@ -226,12 +227,57 @@ static int sun8i_set_fmt(struct snd_soc_dai *dai, unsigned int fmt)
 	return 0;
 }
 
+struct sun8i_codec_clk_div {
+	u8	div;
+	u8	val;
+};
+
+static const struct sun8i_codec_clk_div sun8i_codec_bclk_div[] = {
+	{ .div = 1,	.val = 0 },
+	{ .div = 2,	.val = 1 },
+	{ .div = 4,	.val = 2 },
+	{ .div = 6,	.val = 3 },
+	{ .div = 8,	.val = 4 },
+	{ .div = 12,	.val = 5 },
+	{ .div = 16,	.val = 6 },
+	{ .div = 24,	.val = 7 },
+	{ .div = 32,	.val = 8 },
+	{ .div = 48,	.val = 9 },
+	{ .div = 64,	.val = 10 },
+	{ .div = 96,	.val = 11 },
+	{ .div = 128,	.val = 12 },
+	{ .div = 192,	.val = 13 },
+};
+
+static u8 sun8i_codec_get_bclk_div(struct sun8i_codec *scodec,
+				   unsigned int rate,
+				   unsigned int word_size)
+{
+	unsigned long clk_rate = clk_get_rate(scodec->clk_module);
+	unsigned int div = clk_rate / rate / word_size / 2;
+	unsigned int best_val = 0, best_diff = ~0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(sun8i_codec_bclk_div); i++) {
+		const struct sun8i_codec_clk_div *bdiv = &sun8i_codec_bclk_div[i];
+		unsigned int diff = abs(bdiv->div - div);
+
+		if (diff < best_diff) {
+			best_diff = diff;
+			best_val = bdiv->val;
+		}
+	}
+
+	return best_val;
+}
+
 static int sun8i_codec_hw_params(struct snd_pcm_substream *substream,
 				 struct snd_pcm_hw_params *params,
 				 struct snd_soc_dai *dai)
 {
 	struct sun8i_codec *scodec = snd_soc_codec_get_drvdata(dai->codec);
 	int sample_rate;
+	u8 bclk_div;
 
 	/*
 	 * The CPU DAI handles only a sample of 16 bits. Configure the
@@ -241,6 +287,11 @@ static int sun8i_codec_hw_params(struct snd_pcm_substream *substream,
 			   SUN8I_AIF1CLK_CTRL_AIF1_WORD_SIZ_MASK,
 			   SUN8I_AIF1CLK_CTRL_AIF1_WORD_SIZ_16);
 
+	bclk_div = sun8i_codec_get_bclk_div(scodec, params_rate(params), 16);
+	regmap_update_bits(scodec->regmap, SUN8I_AIF1CLK_CTRL,
+			   SUN8I_AIF1CLK_CTRL_AIF1_BCLK_DIV_MASK,
+			   bclk_div << SUN8I_AIF1CLK_CTRL_AIF1_BCLK_DIV);
+
 	regmap_update_bits(scodec->regmap, SUN8I_AIF1CLK_CTRL,
 			   SUN8I_AIF1CLK_CTRL_AIF1_LRCK_DIV_MASK,
 			   SUN8I_AIF1CLK_CTRL_AIF1_LRCK_DIV_16);
-- 
2.14.3