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m3k: don't use mixer controls for volume control 

According to a forum user, there's an audible click when changing
the volume between -32 and -32.5 dB with some headphones. Fix this
by not (ab)using the DAC digital mixer for volume control.

The mixer only provides an extra -6 dB of hardware volume range,
so the only side effect is that software volume will now kick in
at -32 dB instead of -38 dB.

Change-Id: If24d9bc0058eff3c1a29aefb155a2e378522623c
This commit is contained in:
Aidan MacDonald 2021-09-22 10:39:21 +01:00
parent 0a1d25d27a
commit fd568d90a4
1 changed files with 8 additions and 14 deletions
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22
firmware/drivers/audio/ak4376.c
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@ -83,11 +83,11 @@ void ak4376_open(void)
ak4376_set_pdn_pin(1);
mdelay(1);
static const int init_config[] = {
static const uint8_t init_config[] = {
/* Ensure HPRHZ, HPLHZ are 0 */
AK4376_REG_OUTPUT_MODE, 0x00,
/* Mute all volume controls */
AK4376_REG_MIXER, 0x00,
AK4376_REG_MIXER, AK4376_MIX_LCH | (AK4376_MIX_RCH << 4),
AK4376_REG_LCH_VOLUME, 0x80,
AK4376_REG_RCH_VOLUME, 0x00,
AK4376_REG_AMP_VOLUME, 0x00,
@ -150,14 +150,9 @@ static int round_step_up(int x, int step)
return x - rem;
}
static void calc_volumes(int vol, int* mix, int* dig, int* sw)
static void calc_volumes(int vol, int* dig, int* sw)
{
/* Mixer can divide by 2, which gives an extra -6 dB adjustment */
if(vol < AK4376_DIG_VOLUME_MIN) {
*mix |= AK4376_MIX_HALF;
vol += 60;
}
/* Apply digital volume */
*dig = round_step_up(vol, AK4376_DIG_VOLUME_STEP);
*dig = MIN(*dig, AK4376_DIG_VOLUME_MAX);
*dig = MAX(*dig, AK4376_DIG_VOLUME_MIN);
@ -186,8 +181,8 @@ static int amp_vol_to_hw(int vol)
void ak4376_set_volume(int vol_l, int vol_r)
{
int amp;
int mix_l = AK4376_MIX_LCH, dig_l, sw_l;
int mix_r = AK4376_MIX_RCH, dig_r, sw_r;
int dig_l, sw_l;
int dig_r, sw_r;
if(vol_l <= AK4376_MIN_VOLUME && vol_r <= AK4376_MIN_VOLUME) {
/* Special case for full mute */
@ -202,11 +197,10 @@ void ak4376_set_volume(int vol_l, int vol_r)
amp = MAX(amp, AK4376_AMP_VOLUME_MIN);
/* Other controls are stereo */
calc_volumes(vol_l - amp, &mix_l, &dig_l, &sw_l);
calc_volumes(vol_r - amp, &mix_r, &dig_r, &sw_r);
calc_volumes(vol_l - amp, &dig_l, &sw_l);
calc_volumes(vol_r - amp, &dig_r, &sw_r);
}
ak4376_write(AK4376_REG_MIXER, (mix_l & 0xf) | ((mix_r & 0xf) << 4));
ak4376_write(AK4376_REG_LCH_VOLUME, dig_vol_to_hw(dig_l) | (1 << 7));
ak4376_write(AK4376_REG_RCH_VOLUME, dig_vol_to_hw(dig_r));
ak4376_write(AK4376_REG_AMP_VOLUME, amp_vol_to_hw(amp));