ASoC: sgtl5000: add avc support

The sgtl5000 features an automatic volume control block (AVC), which
reduces loud signals and amplifies low level signals for easier
listening. This patch adds support for this AVC block to the driver.

Apart from the "AVC Switch" control which enables the block following
controls for the configuration of AVC are added:
	+ AVC Threshold Volume: threshold where audio is compressed when
		the measured level is above or expanded when below
	+ AVC Max Gain Volume: maximum gain which can be applied when
		the measured audio level is below threshold
	+ AVC Hard Limiter Switch: when enabled the signal is limited to
		the programmed threshold.
	+ AVC Integrator Response: response time of the integrator

The AVC block is enabled and configured using the DAP_AVC_CTRL and
DAP_AVC_THRESHOLD registers.

Following 2 checkpatch.pl strict checks are ignored because the
indentation style is different for the struct snd_kcontrol_new
definition:
	patch:147: CHECK: Alignment should match open parenthesis
	patch:150: CHECK: Alignment should match open parenthesis
Signed-off-by: Richard Leitner <richard.leitner@skidata.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/sgtl5000.c

@@ -74,6 +74,20 @@ static const struct reg_default sgtl5000_reg_defaults[] = {
 	{ SGTL5000_DAP_AVC_DECAY,		0x0050 },
 };
 
+/* AVC: Threshold dB -> register: pre-calculated values */
+static const u16 avc_thr_db2reg[97] = {
+	0x5168, 0x488E, 0x40AA, 0x39A1, 0x335D, 0x2DC7, 0x28CC, 0x245D, 0x2068,
+	0x1CE2, 0x19BE, 0x16F1, 0x1472, 0x1239, 0x103E, 0x0E7A, 0x0CE6, 0x0B7F,
+	0x0A3F, 0x0922, 0x0824, 0x0741, 0x0677, 0x05C3, 0x0522, 0x0493, 0x0414,
+	0x03A2, 0x033D, 0x02E3, 0x0293, 0x024B, 0x020B, 0x01D2, 0x019F, 0x0172,
+	0x014A, 0x0126, 0x0106, 0x00E9, 0x00D0, 0x00B9, 0x00A5, 0x0093, 0x0083,
+	0x0075, 0x0068, 0x005D, 0x0052, 0x0049, 0x0041, 0x003A, 0x0034, 0x002E,
+	0x0029, 0x0025, 0x0021, 0x001D, 0x001A, 0x0017, 0x0014, 0x0012, 0x0010,
+	0x000E, 0x000D, 0x000B, 0x000A, 0x0009, 0x0008, 0x0007, 0x0006, 0x0005,
+	0x0005, 0x0004, 0x0004, 0x0003, 0x0003, 0x0002, 0x0002, 0x0002, 0x0002,
+	0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0001, 0x0000, 0x0000, 0x0000,
+	0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000, 0x0000};
+
 /* regulator supplies for sgtl5000, VDDD is an optional external supply */
 enum sgtl5000_regulator_supplies {
 	VDDA,
@@ -382,6 +396,65 @@ static int dac_put_volsw(struct snd_kcontrol *kcontrol,
 	return 0;
 }
 
+/*
+ * custom function to get AVC threshold
+ *
+ * The threshold dB is calculated by rearranging the calculation from the
+ * avc_put_threshold function: register_value = 10^(dB/20) * 0.636 * 2^15 ==>
+ * dB = ( fls(register_value) - 14.347 ) * 6.02
+ *
+ * As this calculation is expensive and the threshold dB values may not exeed
+ * 0 to 96 we use pre-calculated values.
+ */
+static int avc_get_threshold(struct snd_kcontrol *kcontrol,
+			     struct snd_ctl_elem_value *ucontrol)
+{
+	struct snd_soc_codec *codec = snd_kcontrol_chip(kcontrol);
+	int db, i;
+	u16 reg = snd_soc_read(codec, SGTL5000_DAP_AVC_THRESHOLD);
+
+	/* register value 0 => -96dB */
+	if (!reg) {
+		ucontrol->value.integer.value[0] = 96;
+		ucontrol->value.integer.value[1] = 96;
+		return 0;
+	}
+
+	/* get dB from register value (rounded down) */
+	for (i = 0; avc_thr_db2reg[i] > reg; i++)
+		;
+	db = i;
+
+	ucontrol->value.integer.value[0] = db;
+	ucontrol->value.integer.value[1] = db;
+
+	return 0;
+}
+
+/*
+ * custom function to put AVC threshold
+ *
+ * The register value is calculated by following formula:
+ *                                    register_value = 10^(dB/20) * 0.636 * 2^15
+ * As this calculation is expensive and the threshold dB values may not exeed
+ * 0 to 96 we use pre-calculated values.
+ */
+static int avc_put_threshold(struct snd_kcontrol *kcontrol,
+			     struct snd_ctl_elem_value *ucontrol)
+{
+	struct snd_soc_codec *codec = snd_kcontrol_chip(kcontrol);
+	int db;
+	u16 reg;
+
+	db = (int)ucontrol->value.integer.value[0];
+	if (db < 0 || db > 96)
+		return -EINVAL;
+	reg = avc_thr_db2reg[db];
+	snd_soc_write(codec, SGTL5000_DAP_AVC_THRESHOLD, reg);
+
+	return 0;
+}
+
 static const DECLARE_TLV_DB_SCALE(capture_6db_attenuate, -600, 600, 0);
 
 /* tlv for mic gain, 0db 20db 30db 40db */
@@ -396,6 +469,12 @@ static const DECLARE_TLV_DB_SCALE(headphone_volume, -5150, 50, 0);
 /* tlv for lineout volume, 31 steps of .5db each */
 static const DECLARE_TLV_DB_SCALE(lineout_volume, -1550, 50, 0);
 
+/* tlv for dap avc max gain, 0db, 6db, 12db */
+static const DECLARE_TLV_DB_SCALE(avc_max_gain, 0, 600, 0);
+
+/* tlv for dap avc threshold, */
+static const DECLARE_TLV_DB_MINMAX(avc_threshold, 0, 9600);
+
 static const struct snd_kcontrol_new sgtl5000_snd_controls[] = {
 	/* SOC_DOUBLE_S8_TLV with invert */
 	{
@@ -434,6 +513,16 @@ static const struct snd_kcontrol_new sgtl5000_snd_controls[] = {
 			0x1f, 1,
 			lineout_volume),
 	SOC_SINGLE("Lineout Playback Switch", SGTL5000_CHIP_ANA_CTRL, 8, 1, 1),
+
+	/* Automatic Volume Control (DAP AVC) */
+	SOC_SINGLE("AVC Switch", SGTL5000_DAP_AVC_CTRL, 0, 1, 0),
+	SOC_SINGLE("AVC Hard Limiter Switch", SGTL5000_DAP_AVC_CTRL, 5, 1, 0),
+	SOC_SINGLE_TLV("AVC Max Gain Volume", SGTL5000_DAP_AVC_CTRL, 12, 2, 0,
+			avc_max_gain),
+	SOC_SINGLE("AVC Integrator Response", SGTL5000_DAP_AVC_CTRL, 8, 3, 0),
+	SOC_SINGLE_EXT_TLV("AVC Threshold Volume", SGTL5000_DAP_AVC_THRESHOLD,
+			0, 96, 0, avc_get_threshold, avc_put_threshold,
+			avc_threshold),
 };
 
 /* mute the codec used by alsa core */