Re: [PATCH] ALSA: hda/realtek: Limit Line In boost and ADC gain on DECENTA MATX03

[Takashi Iwai <tiwai@suse.de>]

On Tue, 13 Oct 2026 14:03:27 +0200,
wangdich9700@163.com wrote:
> 
> From: wangdicheng <wangdicheng@kylinos.cn>
> 
> The DECENTA MATX03 (ALC897, SSID 1e0b:1297) exposes a high gain
> range on both the Line In pin boost and the ADC input amp. Pin 0x1a
> reports nsteps=0x03 with stepsize=0x27, that is 0, 9.75, 19.5 and
> 29.25 dB. ADC 0x08 reports nsteps=0x3f with stepsize=0x02, that is
> 0 to 31.5 dB in 0.5 dB steps, and defaults to 0x3f (maximum). The
> combined 60.75 dB analogue cascade overloads the front-end when the
> source level is high, producing audible harmonic distortion during
> Line In monitoring.
> 
> Add a new fixup alc897_fixup_limit_linein_boost that overrides the amp
> capabilities of the Line In and external Mic pins to nsteps=1 (max
> ~11.75 dB), and also limits the ADC input amp to nsteps=1 (max ~0.5 dB).
> The total gain drops from 60.75 dB to ~12.25 dB, eliminating the
> clipping. Internal and dock mic pins are excluded to avoid affecting
> built-in microphones.
> 
> Tested on the affected machine: with the fixup applied, Line In
> recording at maximum source volume is clean, and dmesg confirms the
> fixup is picked:
> 
>   ALC897: picked fixup alc897-limit-linein-boost (SSID)
> 
> Signed-off-by: wangdicheng <wangdicheng@kylinos.cn>
> ---
>  sound/hda/codecs/realtek/alc662.c | 50 +++++++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
> 
> diff --git a/sound/hda/codecs/realtek/alc662.c b/sound/hda/codecs/realtek/alc662.c
> index eff7c83b9c59..a140891d51fa 100644
> --- a/sound/hda/codecs/realtek/alc662.c
> +++ b/sound/hda/codecs/realtek/alc662.c
> @@ -198,6 +198,49 @@ static void alc897_fixup_lenovo_headset_mode(struct hda_codec *codec,
>  	}
>  }
>  
> +static void alc897_fixup_limit_linein_boost(struct hda_codec *codec,
> +					    const struct hda_fixup *fix, int action)
> +{
> +	struct alc_spec *spec = codec->spec;
> +	struct auto_pin_cfg *cfg = &spec->gen.autocfg;
> +	int i;
> +
> +	if (action != HDA_FIXUP_ACT_PROBE)
> +		return;
> +
> +	for (i = 0; i < cfg->num_inputs; i++) {
> +		hda_nid_t nid = cfg->inputs[i].pin;
> +		unsigned int defcfg;
> +
> +		if (cfg->inputs[i].type != AUTO_PIN_LINE_IN &&
> +		    cfg->inputs[i].type != AUTO_PIN_MIC)
> +			continue;
> +
> +		defcfg = snd_hda_codec_get_pincfg(codec, nid);
> +		if (snd_hda_get_input_pin_attr(defcfg) == INPUT_PIN_ATTR_INT ||
> +		    snd_hda_get_input_pin_attr(defcfg) == INPUT_PIN_ATTR_DOCK)
> +			continue;
> +
> +		snd_hda_override_amp_caps(codec, nid, HDA_INPUT,
> +					  (0x00 << AC_AMPCAP_OFFSET_SHIFT) |
> +					  (0x01 << AC_AMPCAP_NUM_STEPS_SHIFT) |
> +					  (0x2f << AC_AMPCAP_STEP_SIZE_SHIFT) |
> +					  (0 << AC_AMPCAP_MUTE_SHIFT));
> +	}
> +
> +	for (i = 0; i < spec->gen.num_all_adcs; i++) {
> +		hda_nid_t adc = spec->gen.all_adcs[i];
> +		unsigned int caps;
> +
> +		caps = query_amp_caps(codec, adc, HDA_INPUT);
> +		if ((caps & AC_AMPCAP_NUM_STEPS) >> AC_AMPCAP_NUM_STEPS_SHIFT > 1) {
> +			caps &= ~AC_AMPCAP_NUM_STEPS;
> +			caps |= (0x01 << AC_AMPCAP_NUM_STEPS_SHIFT);
> +			snd_hda_override_amp_caps(codec, adc, HDA_INPUT, caps);
> +		}
> +	}
> +}
> +

I guess there aren't so many pins and ADCs, and the quirk is very
specific to the model, so you can just write a few
snd_hda_override_amp_caps() for the fixed hard-coded NIDs.

The alc269_fixup_limit_int_mic_boost() is applied to lots of different
models, hence it handles in a generic way, OTOH.

>  static const struct hda_quirk alc662_fixup_tbl[] = {
> @@ -859,6 +907,7 @@ static const struct hda_quirk alc662_fixup_tbl[] = {
>  	SND_PCI_QUIRK(0x1c6c, 0x1239, "Compaq N14JP6-V2", ALC897_FIXUP_HP_HSMIC_VERB),
>  	SND_PCI_QUIRK(0x1e63, 0x6d9a, "F+ FLAPTOP r", ALC897_FIXUP_HP_HSMIC_VERB),
>  	SND_PCI_QUIRK(0x1f66, 0x0202, "Beelink SER6 Max 6900", ALC897_FIXUP_BEELINK_SER6_AMP),
> +	SND_PCI_QUIRK(0x1e0b, 0x1297, "DECENTA MATX03", ALC897_FIXUP_LIMIT_LINEIN_BOOST),

The table is sorted in PCI SSID order, so please put at the right
position.

> @@ -954,6 +1003,7 @@ static const struct hda_model_fixup alc662_fixup_models[] = {
>  	{.id = ALC662_FIXUP_LENOVO_MULTI_CODECS, .name = "dual-codecs"},
>  	{.id = ALC669_FIXUP_ACER_ASPIRE_ETHOS, .name = "aspire-ethos"},
>  	{.id = ALC897_FIXUP_UNIS_H3C_X500S, .name = "unis-h3c-x500s"},
> +	{.id = ALC897_FIXUP_LIMIT_LINEIN_BOOST, .name = "alc897-limit-linein-boost"},
>  	{}
>  };

Nowadays we don't want a model name addition unless it's really
needed.  The existing quirk can be applied with an alias instead of a
model name string.


thanks,

Takashi