ASoC: pcm512x: Avoid the PLL for the DAC clock, if possible

[deliverable/linux.git] / sound / soc / codecs / pcm512x.c

diff --git a/sound/soc/codecs/pcm512x.c b/sound/soc/codecs/pcm512x.c
index 66dd036f014115c7f8d1489cada86aa39fa5cf31..8b474196d52a2ed4c1e1098e4682986178099ac7 100644 (file)
--- a/sound/soc/codecs/pcm512x.c
+++ b/sound/soc/codecs/pcm512x.c
@@ -105,6 +105,7 @@ static const struct reg_default pcm512x_reg_defaults[] = {
        { PCM512x_VCOM_CTRL_2,       0x01 },
        { PCM512x_BCLK_LRCLK_CFG,    0x00 },
        { PCM512x_MASTER_MODE,       0x7c },
+       { PCM512x_GPIO_DACIN,        0x00 },
        { PCM512x_GPIO_PLLIN,        0x00 },
        { PCM512x_SYNCHRONIZE,       0x10 },
        { PCM512x_PLL_COEFF_0,       0x00 },
@@ -138,6 +139,7 @@ static bool pcm512x_readable(struct device *dev, unsigned int reg)
        case PCM512x_MASTER_MODE:
        case PCM512x_PLL_REF:
        case PCM512x_DAC_REF:
+       case PCM512x_GPIO_DACIN:
        case PCM512x_GPIO_PLLIN:
        case PCM512x_SYNCHRONIZE:
        case PCM512x_PLL_COEFF_0:
@@ -659,6 +661,37 @@ done:
        return 0;
 }
 
+static unsigned long pcm512x_pllin_dac_rate(struct snd_soc_dai *dai,
+                                           unsigned long osr_rate,
+                                           unsigned long pllin_rate)
+{
+       struct snd_soc_codec *codec = dai->codec;
+       struct pcm512x_priv *pcm512x = snd_soc_codec_get_drvdata(codec);
+       unsigned long dac_rate;
+
+       if (!pcm512x->pll_out)
+               return 0; /* no PLL to bypass, force SCK as DAC input */
+
+       if (pllin_rate % osr_rate)
+               return 0; /* futile, quit early */
+
+       /* run DAC no faster than 6144000 Hz */
+       for (dac_rate = rounddown(6144000, osr_rate);
+            dac_rate;
+            dac_rate -= osr_rate) {
+
+               if (pllin_rate / dac_rate > 128)
+                       return 0; /* DAC divider would be too big */
+
+               if (!(pllin_rate % dac_rate))
+                       return dac_rate;
+
+               dac_rate -= osr_rate;
+       }
+
+       return 0;
+}
+
 static int pcm512x_set_dividers(struct snd_soc_dai *dai,
                                struct snd_pcm_hw_params *params)
 {
@@ -672,6 +705,7 @@ static int pcm512x_set_dividers(struct snd_soc_dai *dai,
        unsigned long bclk_rate;
        unsigned long sample_rate;
        unsigned long osr_rate;
+       unsigned long dacsrc_rate;
        int bclk_div;
        int lrclk_div;
        int dsp_div;
@@ -679,11 +713,10 @@ static int pcm512x_set_dividers(struct snd_soc_dai *dai,
        unsigned long dac_rate;
        int ncp_div;
        int osr_div;
-       unsigned long dac_mul;
-       unsigned long sck_mul;
        int ret;
        int idac;
        int fssp;
+       int gpio;
 
        lrclk_div = snd_soc_params_to_frame_size(params);
        if (lrclk_div == 0) {
@@ -772,31 +805,72 @@ static int pcm512x_set_dividers(struct snd_soc_dai *dai,
        /* run DSP no faster than 50 MHz */
        dsp_div = mck_rate > 50000000 ? 2 : 1;
 
-       /* run DAC no faster than 6144000 Hz */
-       dac_mul = 6144000 / osr_rate;
-       sck_mul = sck_rate / osr_rate;
-       for (; dac_mul; dac_mul--) {
-               if (!(sck_mul % dac_mul))
-                       break;
-       }
-       if (!dac_mul) {
-               dev_err(dev, "Failed to find DAC rate\n");
-               return -EINVAL;
-       }
+       dac_rate = pcm512x_pllin_dac_rate(dai, osr_rate, pllin_rate);
+       if (dac_rate) {
+               /* the desired clock rate is "compatible" with the pll input
+                * clock, so use that clock as dac input instead of the pll
+                * output clock since the pll will introduce jitter and thus
+                * noise.
+                */
+               dev_dbg(dev, "using pll input as dac input\n");
+               ret = regmap_update_bits(pcm512x->regmap, PCM512x_DAC_REF,
+                                        PCM512x_SDAC, PCM512x_SDAC_GPIO);
+               if (ret != 0) {
+                       dev_err(codec->dev,
+                               "Failed to set gpio as dacref: %d\n", ret);
+                       return ret;
+               }
 
-       dac_rate = dac_mul * osr_rate;
-       dev_dbg(dev, "dac_rate %lu sample_rate %lu\n", dac_rate, sample_rate);
+               gpio = PCM512x_GREF_GPIO1 + pcm512x->pll_in - 1;
+               ret = regmap_update_bits(pcm512x->regmap, PCM512x_GPIO_DACIN,
+                                        PCM512x_GREF, gpio);
+               if (ret != 0) {
+                       dev_err(codec->dev,
+                               "Failed to set gpio %d as dacin: %d\n",
+                               pcm512x->pll_in, ret);
+                       return ret;
+               }
+
+               dacsrc_rate = pllin_rate;
+       } else {
+               /* run DAC no faster than 6144000 Hz */
+               unsigned long dac_mul = 6144000 / osr_rate;
+               unsigned long sck_mul = sck_rate / osr_rate;
+
+               for (; dac_mul; dac_mul--) {
+                       if (!(sck_mul % dac_mul))
+                               break;
+               }
+               if (!dac_mul) {
+                       dev_err(dev, "Failed to find DAC rate\n");
+                       return -EINVAL;
+               }
 
-       dac_div = DIV_ROUND_CLOSEST(sck_rate, dac_rate);
+               dac_rate = dac_mul * osr_rate;
+               dev_dbg(dev, "dac_rate %lu sample_rate %lu\n",
+                       dac_rate, sample_rate);
+
+               ret = regmap_update_bits(pcm512x->regmap, PCM512x_DAC_REF,
+                                        PCM512x_SDAC, PCM512x_SDAC_SCK);
+               if (ret != 0) {
+                       dev_err(codec->dev,
+                               "Failed to set sck as dacref: %d\n", ret);
+                       return ret;
+               }
+
+               dacsrc_rate = sck_rate;
+       }
+
+       dac_div = DIV_ROUND_CLOSEST(dacsrc_rate, dac_rate);
        if (dac_div > 128) {
                dev_err(dev, "Failed to find DAC divider\n");
                return -EINVAL;
        }
 
-       ncp_div = DIV_ROUND_CLOSEST(sck_rate / dac_div, 1536000);
-       if (ncp_div > 128 || sck_rate / dac_div / ncp_div > 2048000) {
+       ncp_div = DIV_ROUND_CLOSEST(dacsrc_rate / dac_div, 1536000);
+       if (ncp_div > 128 || dacsrc_rate / dac_div / ncp_div > 2048000) {
                /* run NCP no faster than 2048000 Hz, but why? */
-               ncp_div = DIV_ROUND_UP(sck_rate / dac_div, 2048000);
+               ncp_div = DIV_ROUND_UP(dacsrc_rate / dac_div, 2048000);
                if (ncp_div > 128) {
                        dev_err(dev, "Failed to find NCP divider\n");
                        return -EINVAL;
@@ -1011,13 +1085,6 @@ static int pcm512x_hw_params(struct snd_pcm_substream *substream,
        if (ret != 0)
                return ret;
 
-       ret = regmap_update_bits(pcm512x->regmap, PCM512x_DAC_REF,
-                                PCM512x_SDAC, PCM512x_SDAC_SCK);
-       if (ret != 0) {
-               dev_err(codec->dev, "Failed to set sck as dacref: %d\n", ret);
-               return ret;
-       }
-
        if (pcm512x->pll_out) {
                ret = regmap_update_bits(pcm512x->regmap, PCM512x_PLL_REF,
                                         PCM512x_SREF, PCM512x_SREF_GPIO);