ASoC: sn95031: Add support for reading mic bias

This patch adds support to read the mic bias voltage
when a jack is inserted. It uses ADC to measure.

Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Harsha Priya <priya.harsha@intel.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 123 insertions, 4 deletions

diff --git a/sound/soc/codecs/sn95031.c b/sound/soc/codecs/sn95031.c
index b49d79017d3..4cc00177ee3 100644
--- a/sound/soc/codecs/sn95031.c
+++ b/sound/soc/codecs/sn95031.c
@@ -40,12 +40,129 @@
 #define SN95031_RATES (SNDRV_PCM_RATE_48000 | SNDRV_PCM_RATE_44100)
 #define SN95031_FORMATS (SNDRV_PCM_FMTBIT_S24_LE | SNDRV_PCM_FMTBIT_S16_LE)
 
+/* adc helper functions */
+
+/* enables mic bias voltage */
+static void sn95031_enable_mic_bias(struct snd_soc_codec *codec)
+{
+        snd_soc_write(codec, SN95031_VAUD, BIT(2)|BIT(1)|BIT(0));
+        snd_soc_update_bits(codec, SN95031_MICBIAS, BIT(2), BIT(2));
+}
+
+/* Enable/Disable the ADC depending on the argument */
+static void configure_adc(struct snd_soc_codec *sn95031_codec, int val)
+{
+        int value = snd_soc_read(sn95031_codec, SN95031_ADC1CNTL1);
+
+        if (val) {
+                /* Enable and start the ADC */
+                value |= (SN95031_ADC_ENBL | SN95031_ADC_START);
+                value &= (~SN95031_ADC_NO_LOOP);
+        } else {
+                /* Just stop the ADC */
+                value &= (~SN95031_ADC_START);
+        }
+        snd_soc_write(sn95031_codec, SN95031_ADC1CNTL1, value);
+}
+
 /*
- * todo:
- * capture paths
- * jack detection
- * PM functions
+ * finds an empty channel for conversion
+ * If the ADC is not enabled then start using 0th channel
+ * itself. Otherwise find an empty channel by looking for a
+ * channel in which the stopbit is set to 1. returns the index
+ * of the first free channel if succeeds or an error code.
+ *
+ * Context: can sleep
+ *
  */
+static int find_free_channel(struct snd_soc_codec *sn95031_codec)
+{
+        int ret = 0, i, value;
+
+        /* check whether ADC is enabled */
+        value = snd_soc_read(sn95031_codec, SN95031_ADC1CNTL1);
+
+        if ((value & SN95031_ADC_ENBL) == 0)
+                return 0;
+
+        /* ADC is already enabled; Looking for an empty channel */
+        for (i = 0; i < SN95031_ADC_CHANLS_MAX; i++) {
+                value = snd_soc_read(sn95031_codec,
+                                SN95031_ADC_CHNL_START_ADDR + i);
+                if (value & SN95031_STOPBIT_MASK) {
+                        ret = i;
+                        break;
+                }
+        }
+        return (ret > SN95031_ADC_LOOP_MAX) ? (-EINVAL) : ret;
+}
+
+/* Initialize the ADC for reading micbias values. Can sleep. */
+static int sn95031_initialize_adc(struct snd_soc_codec *sn95031_codec)
+{
+        int base_addr, chnl_addr;
+        int value;
+        static int channel_index;
+
+        /* Index of the first channel in which the stop bit is set */
+        channel_index = find_free_channel(sn95031_codec);
+        if (channel_index < 0) {
+                pr_err("No free ADC channels");
+                return channel_index;
+        }
+
+        base_addr = SN95031_ADC_CHNL_START_ADDR + channel_index;
+
+        if (!(channel_index == 0 || channel_index ==  SN95031_ADC_LOOP_MAX)) {
+                /* Reset stop bit for channels other than 0 and 12 */
+                value = snd_soc_read(sn95031_codec, base_addr);
+                /* Set the stop bit to zero */
+                snd_soc_write(sn95031_codec, base_addr, value & 0xEF);
+                /* Index of the first free channel */
+                base_addr++;
+                channel_index++;
+        }
+
+        /* Since this is the last channel, set the stop bit
+           to 1 by ORing the DIE_SENSOR_CODE with 0x10 */
+        snd_soc_write(sn95031_codec, base_addr,
+                                SN95031_AUDIO_DETECT_CODE | 0x10);
+
+        chnl_addr = SN95031_ADC_DATA_START_ADDR + 2 * channel_index;
+        pr_debug("mid_initialize : %x", chnl_addr);
+        configure_adc(sn95031_codec, 1);
+        return chnl_addr;
+}
+
+
+/* reads the ADC registers and gets the mic bias value in mV. */
+static unsigned int sn95031_get_mic_bias(struct snd_soc_codec *codec)
+{
+        u16 adc_adr = sn95031_initialize_adc(codec);
+        u16 adc_val1, adc_val2;
+        unsigned int mic_bias;
+
+        sn95031_enable_mic_bias(codec);
+
+        /* Enable the sound card for conversion before reading */
+        snd_soc_write(codec, SN95031_ADC1CNTL3, 0x05);
+        /* Re-toggle the RRDATARD bit */
+        snd_soc_write(codec, SN95031_ADC1CNTL3, 0x04);
+
+        /* Read the higher bits of data */
+        msleep(1000);
+        adc_val1 = snd_soc_read(codec, adc_adr);
+        adc_adr++;
+        adc_val2 = snd_soc_read(codec, adc_adr);
+
+        /* Adding lower two bits to the higher bits */
+        mic_bias = (adc_val1 << 2) + (adc_val2 & 3);
+        mic_bias = (mic_bias * SN95031_ADC_ONE_LSB_MULTIPLIER) / 1000;
+        pr_debug("mic bias = %dmV\n", mic_bias);
+        return mic_bias;
+}
+EXPORT_SYMBOL_GPL(sn95031_get_mic_bias);
+/*end - adc helper functions */
 
 static inline unsigned int sn95031_read(struct snd_soc_codec *codec,
                         unsigned int reg)
@@ -663,6 +780,8 @@ static inline void sn95031_enable_jack_btn(struct snd_soc_codec *codec)
 
 static int sn95031_get_headset_state(struct snd_soc_jack *mfld_jack)
 {
+        int micbias = sn95031_get_mic_bias(mfld_jack->codec);
+
         /* Defaulting to HEADSET for now.
          * will change after adding soc-jack detection apis */
         int jack_type = SND_JACK_HEADSET;