ASoC: sgtl5000: Calculate Lineout Channel Output Level

Currently LO_VOL_* stays at it's default (0x4 each) but this should be
calculated after setting VAG_VAL and LO_VAGCNTRL.
LO_VOL_* = 40 * log10(VAG_VAL / LO_VAGCNTRL) + 15

To avoid the log10 operation a table for all valid register values is
precalculated which contains the corresponding value
(VAG_VAL * 100 / LO_VAGCNTRL).

Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/sound/soc/codecs/sgtl5000.c b/sound/soc/codecs/sgtl5000.c
index bab2b5e5b312..1b883437dcbe 100644
--- a/sound/soc/codecs/sgtl5000.c
+++ b/sound/soc/codecs/sgtl5000.c
@@ -1092,6 +1092,19 @@ static bool sgtl5000_readable(struct device *dev, unsigned int reg)
 }
 
 /*
+ * This precalculated table contains all (vag_val * 100 / lo_calcntrl) results
+ * to select an appropriate lo_vol_* in SGTL5000_CHIP_LINE_OUT_VOL
+ * The calculatation was done for all possible register values which
+ * is the array index and the following formula: 10^((idx−15)/40) * 100
+ */
+static const u8 vol_quot_table[] = {
+        42, 45, 47, 50, 53, 56, 60, 63,
+        67, 71, 75, 79, 84, 89, 94, 100,
+        106, 112, 119, 126, 133, 141, 150, 158,
+        168, 178, 188, 200, 211, 224, 237, 251
+};
+
+/*
  * sgtl5000 has 3 internal power supplies:
  * 1. VAG, normally set to vdda/2
  * 2. charge pump, set to different value
@@ -1112,6 +1125,9 @@ static int sgtl5000_set_power_regs(struct snd_soc_codec *codec)
         u16 lreg_ctrl;
         int vag;
         int lo_vag;
+        int vol_quot;
+        int lo_vol;
+        size_t i;
         struct sgtl5000_priv *sgtl5000 = snd_soc_codec_get_drvdata(codec);
 
         vdda  = regulator_get_voltage(sgtl5000->supplies[VDDA].consumer);
@@ -1216,6 +1232,28 @@ static int sgtl5000_set_power_regs(struct snd_soc_codec *codec)
                         SGTL5000_LINE_OUT_CURRENT_360u <<
                                 SGTL5000_LINE_OUT_CURRENT_SHIFT);
 
+        /*
+         * Set lineout output level in range (0..31)
+         * the same value is used for right and left channel
+         *
+         * Searching for a suitable index solving this formula:
+         * idx = 40 * log10(vag_val / lo_cagcntrl) + 15
+         */
+        vol_quot = (vag * 100) / lo_vag;
+        lo_vol = 0;
+        for (i = 0; i < ARRAY_SIZE(vol_quot_table); i++) {
+                if (vol_quot >= vol_quot_table[i])
+                        lo_vol = i;
+                else
+                        break;
+        }
+
+        snd_soc_update_bits(codec, SGTL5000_CHIP_LINE_OUT_VOL,
+                SGTL5000_LINE_OUT_VOL_RIGHT_MASK |
+                SGTL5000_LINE_OUT_VOL_LEFT_MASK,
+                lo_vol << SGTL5000_LINE_OUT_VOL_RIGHT_SHIFT |
+                lo_vol << SGTL5000_LINE_OUT_VOL_LEFT_SHIFT);
+
         return 0;
 }