[PATCH] ASoC: max98090: keep the MIC boost across mic input power-up

[LiangCheng Wang <zaq14760@gmail.com>]

PA1EN/PA2EN select both the MIC1/MIC2 preamp enable and its gain
(0 = off, 1 = 0 dB, 2 = +20 dB, 3 = +30 dB). "MICn Boost Volume" keeps
the selected gain in max98090->pa1en/pa2en while the input is off, and
max98090_micinput_event() writes it to the field when the "MICn Input"
widget powers up.

The event handler also reads the field back to keep the stored gain in
sync ("Update for volatile"), but it does so on POST_PMU and POST_PMD.
The widget drives PA1EN/PA2EN as a single enable bit, the low bit of
the field, so at both points DAPM has just rewritten it:

  - POST_PMU: DAPM has set the field to 1, so the read-back stores
    0 dB and the handler then restores 0 dB.
  - POST_PMD: DAPM has cleared the low bit, so a +30 dB (3) gain reads
    back as +20 dB (2).

As a result every capture starts at 0 dB: a boost set while the input is
powered down, e.g. restored by alsactl or an audio HAL at boot, never
takes effect, and one changed during capture is lost at the next
power-up.

Read the field back on PRE_PMD instead, while it still holds the active
gain, and only restore the stored gain on POST_PMU.

Tested on i.MX95 with a MAX98090 headset mic on MIC1, running NXP's
6.18.38 vendor kernel (max98090_micinput_event() is the same as in
mainline): with MIC1 Boost Volume set to 2 (+30 dB) before capture,
register 0x10 reads 0x20 (0 dB) during capture without this change and
0x60 (+30 dB) with it, and a boost changed during capture is kept for
the next capture.

Fixes: 685e42154dcf ("ASoC: Replace max98090 Device Driver")
Signed-off-by: LiangCheng Wang <zaq14760@gmail.com>
---
 sound/soc/codecs/max98090.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index a985853e48eb6fc4b02c8f148f73fb70bf18168b..3ed513f6d81cd6bdc85caea12f38030f85cdda13 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -743,14 +743,6 @@ static int max98090_micinput_event(struct snd_soc_dapm_widget *w,
 	else
 		val = (val & M98090_MIC_PA2EN_MASK) >> M98090_MIC_PA2EN_SHIFT;
 
-	if (val >= 1) {
-		if (w->reg == M98090_REG_MIC1_INPUT_LEVEL) {
-			max98090->pa1en = val - 1; /* Update for volatile */
-		} else {
-			max98090->pa2en = val - 1; /* Update for volatile */
-		}
-	}
-
 	switch (event) {
 	case SND_SOC_DAPM_POST_PMU:
 		/* If turning on, set to most recently selected volume */
@@ -759,6 +751,14 @@ static int max98090_micinput_event(struct snd_soc_dapm_widget *w,
 		else
 			val = max98090->pa2en + 1;
 		break;
+	case SND_SOC_DAPM_PRE_PMD:
+		if (val >= 1) {
+			if (w->reg == M98090_REG_MIC1_INPUT_LEVEL)
+				max98090->pa1en = val - 1;
+			else
+				max98090->pa2en = val - 1;
+		}
+		return 0;
 	case SND_SOC_DAPM_POST_PMD:
 		/* If turning off, turn off */
 		val = 0;
@@ -1121,11 +1121,13 @@ static const struct snd_soc_dapm_widget max98090_dapm_widgets[] = {
 
 	SND_SOC_DAPM_PGA_E("MIC1 Input", M98090_REG_MIC1_INPUT_LEVEL,
 		M98090_MIC_PA1EN_SHIFT, 0, NULL, 0, max98090_micinput_event,
-		SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_POST_PMD),
+		SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD |
+		SND_SOC_DAPM_POST_PMD),
 
 	SND_SOC_DAPM_PGA_E("MIC2 Input", M98090_REG_MIC2_INPUT_LEVEL,
 		M98090_MIC_PA2EN_SHIFT, 0, NULL, 0, max98090_micinput_event,
-		SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_POST_PMD),
+		SND_SOC_DAPM_POST_PMU | SND_SOC_DAPM_PRE_PMD |
+		SND_SOC_DAPM_POST_PMD),
 
 	SND_SOC_DAPM_MIXER("LINEA Mixer", SND_SOC_NOPM, 0, 0,
 		&max98090_linea_mixer_controls[0],

---
base-commit: b3dfbde62cf1981c4638939c159dfd087b7a72e9
change-id: 20261110-max98090-mic-boost-c4653dfae09c

Best regards,
-- 
LiangCheng Wang <zaq14760@gmail.com>