ENGR00309468-2 ASoC: fsl_spdif: Add sysclk_df divsor support for sysclk usage

The sysclk, which could be connected to IPG clock, is one of the eight
clocks on the inner clock mux of SPDIF. Previously we forbade the usage
of this clock due to imperfect clock selecting function.

This patch adds the sysclk_df divisor so as to complete sysclk function.

[ In order to potect those clocks from other modules and the situation
  when SPDIF root clock is shared with other module (ASRC on imx6sx for
  example) that demands us to fix the clock and not to change its rate,
  starting from now on, we no longer use clk_round() and clk_set_rate(). ]

Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>
(cherry picked from commit 3092f062768d7c4312c54c7ec2c5f9acfbbf7e69)

1 files changed, 47 insertions, 42 deletions

diff --git a/sound/soc/fsl/fsl_spdif.c b/sound/soc/fsl/fsl_spdif.c
index 4f42bb7ea6a4..c1baba2ca029 100644
--- a/sound/soc/fsl/fsl_spdif.c
+++ b/sound/soc/fsl/fsl_spdif.c
@@ -78,6 +78,7 @@ struct fsl_spdif_priv {
 	struct regmap *regmap;
 	bool dpll_locked;
 	u8 txclk_div[SPDIF_TXRATE_MAX];
+	u8 sysclk_df[SPDIF_TXRATE_MAX];
 	u8 txclk_src[SPDIF_TXRATE_MAX];
 	u8 rxclk_src;
 	struct clk *txclk[SPDIF_TXRATE_MAX];
@@ -354,8 +355,7 @@ static int spdif_set_sample_rate(struct snd_pcm_substream *substream,
 	struct platform_device *pdev = spdif_priv->pdev;
 	unsigned long csfs = 0;
 	u32 stc, mask, rate;
-	u8 clk, div;
-	int ret;
+	u8 clk, div, df;
 
 	switch (sample_rate) {
 	case 32000:
@@ -387,19 +387,10 @@ static int spdif_set_sample_rate(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	}
 
-	/*
-	 * The S/PDIF block needs a clock of 64 * fs * div.  The S/PDIF block
-	 * will divide by (div).  So request 64 * fs * (div+1) which will
-	 * get rounded.
-	 */
-	ret = clk_set_rate(spdif_priv->txclk[rate], 64 * sample_rate * (div + 1));
-	if (ret) {
-		dev_err(&pdev->dev, "failed to set tx clock rate\n");
-		return ret;
-	}
+	df = spdif_priv->sysclk_df[rate];
 
 	dev_dbg(&pdev->dev, "expected clock rate = %d\n",
-			(64 * sample_rate * div));
+			(64 * sample_rate * div * df));
 	dev_dbg(&pdev->dev, "actual clock rate = %ld\n",
 			clk_get_rate(spdif_priv->txclk[rate]));
 
@@ -411,6 +402,13 @@ static int spdif_set_sample_rate(struct snd_pcm_substream *substream,
 	mask = STC_TXCLK_ALL_EN_MASK | STC_TXCLK_SRC_MASK | STC_TXCLK_DIV_MASK;
 	regmap_update_bits(regmap, REG_SPDIF_STC, mask, stc);
 
+	/* The min of df should be 2 if valid */
+	if (df >= 2) {
+		regmap_update_bits(regmap, REG_SPDIF_STC,
+				   STC_SYSCLK_DIV_MASK, STC_SYSCLK_DIV(df));
+		dev_dbg(&pdev->dev, "use df %d clk %d\n", df, clk);
+	}
+
 	dev_dbg(&pdev->dev, "set sample rate to %d\n", sample_rate);
 
 	return 0;
@@ -1013,40 +1011,51 @@ static u32 fsl_spdif_txclk_caldiv(struct fsl_spdif_priv *spdif_priv,
 				enum spdif_txrate index)
 {
 	const u32 rate[] = { 32000, 44100, 48000 };
-	u64 rate_ideal, rate_actual, sub;
+	bool is_sysclk = clk == spdif_priv->sysclk;
+	u64 rate_actual, sub;
+	u32 df_min, df_max, df;
 	u32 div, arate;
 
-	for (div = 1; div <= 128; div++) {
-		rate_ideal = rate[index] * (div + 1) * 64;
-		rate_actual = clk_round_rate(clk, rate_ideal);
+	/* The sysclk has an extra divisor [2, 512] */
+	df_min = is_sysclk ? 2 : 1;
+	df_max = is_sysclk ? 512 : 1;
 
-		arate = rate_actual / 64;
-		arate /= div;
+	for (df = df_min; df <= df_max; df++) {
+		for (div = 1; div <= 128; div++) {
+			rate_actual = clk_get_rate(clk);
 
-		if (arate == rate[index]) {
-			/* We are lucky */
-			savesub = 0;
-			spdif_priv->txclk_div[index] = div;
-			break;
-		} else if (arate / rate[index] == 1) {
-			/* A little bigger than expect */
-			sub = (arate - rate[index]) * 100000;
-			do_div(sub, rate[index]);
-			if (sub < savesub) {
+			arate = rate_actual / 64;
+			arate /= df * div;
+
+			if (arate == rate[index]) {
+				/* We are lucky */
+				savesub = 0;
+				spdif_priv->txclk_div[index] = div;
+				spdif_priv->sysclk_df[index] = df;
+				goto out;
+			} else if (arate / rate[index] == 1) {
+				/* A little bigger than expect */
+				sub = (arate - rate[index]) * 100000;
+				do_div(sub, rate[index]);
+				if (sub >= savesub)
+					continue;
 				savesub = sub;
 				spdif_priv->txclk_div[index] = div;
-			}
-		} else if (rate[index] / arate == 1) {
-			/* A little smaller than expect */
-			sub = (rate[index] - arate) * 100000;
-			do_div(sub, rate[index]);
-			if (sub < savesub) {
+				spdif_priv->sysclk_df[index] = df;
+			} else if (rate[index] / arate == 1) {
+				/* A little smaller than expect */
+				sub = (rate[index] - arate) * 100000;
+				do_div(sub, rate[index]);
+				if (sub >= savesub)
+					continue;
 				savesub = sub;
 				spdif_priv->txclk_div[index] = div;
+				spdif_priv->sysclk_df[index] = df;
 			}
 		}
 	}
 
+out:
 	return savesub;
 }
 
@@ -1071,13 +1080,6 @@ static int fsl_spdif_probe_txclk(struct fsl_spdif_priv *spdif_priv,
 		if (!clk_get_rate(clk))
 			continue;
 
-		/* TODO: We here ignore sysclk source due to imperfect clock
-		 * selecting mechanism: sysclk is a bit different which we can
-		 * not change its clock rate but use another inner divider to
-		 * derive a proper clock rate. */
-		if (i == SPDIF_CLK_SRC_SYSCLK)
-			continue;
-
 		ret = fsl_spdif_txclk_caldiv(spdif_priv, clk, savesub, index);
 		if (savesub == ret)
 			continue;
@@ -1095,6 +1097,9 @@ static int fsl_spdif_probe_txclk(struct fsl_spdif_priv *spdif_priv,
 			spdif_priv->txclk_src[index], rate[index]);
 	dev_dbg(&pdev->dev, "use divisor %d for %dHz sample rate\n",
 			spdif_priv->txclk_div[index], rate[index]);
+	if (spdif_priv->txclk[index] == spdif_priv->sysclk)
+		dev_dbg(&pdev->dev, "use sysclk_df %d for %dHz sample rate\n",
+				spdif_priv->sysclk_df[index], rate[index]);
 
 	return 0;
 }