Re: [alsa-devel] [PATCH 3/4] ASoC: msm8916-wcd-analog: Simplify MIC BIAS Internal

[Stephan Gerhold <stephan@gerhold.net>]

On Tue, Jan 14, 2020 at 01:03:22PM +0000, Srinivas Kandagatla wrote:
> 
> 
> On 14/01/2020 12:08, Stephan Gerhold wrote:
> > On Tue, Jan 14, 2020 at 10:54:44AM +0000, Srinivas Kandagatla wrote:
> > > 
> > > 
> > > On 11/01/2020 16:40, Stephan Gerhold wrote:
> > > > At the moment, MIC BIAS Internal* and MIC BIAS External* both reference
> > > > the same register, and have a part of their initialization sequence
> > > > duplicated.
> > > > 
> > > > In general, the sequence for enabling MIC BIAS InternalX seems to be:
> > > >     1. Enable MIC BIAS ExternalX
> > > >     2. Enable internal RBIAS resistor
> > > 
> > > Does not sound correct to me.
> > > 
> > > What external means here is if the MICBIAS has external pull up resistor or
> > > not. And this is very much board specific. In order for driver to
> > > enable/disable internal pull up resistor in such cases we use two dapm paths
> > > to differentiate it.
> > > 
> > 
> > You are right. Maybe the naming is a bit confusing here.
> > Let me try to clarify it:
> > 
> > If I understand it correctly, setting the MICB_EN bit in CDC_A_MICB_1_EN
> > enables the MIC_BIAS1 supply. This supply can be either used with an
> > external pull up resistor ("MIC BIAS External1") or with the internal
> > pull up resistor ("MIC BIAS Internal1"). Which one of them, is board-specific.
> > 
> > To use the internal pull up resistor, we need to set the TX1_INT_RBIAS_EN
> > bit in CDC_A_MICB_1_INT_RBIAS additionally.
> > 
> > In other words, the sequence for enabling MIC BIAS Internal1 is:
> >    I1. Enable MIC_BIAS1 supply (MICB_EN bit in CDC_A_MICB_1_EN)
> >    I2. Enable internal RBIAS (TX1_INT_RBIAS_EN bit in CDC_A_MICB_1_INT_RBIAS)
> > 
> > The sequence for enabling MIC BIAS External1 is:
> >    E1. Enable MIC_BIAS1 supply (MICB_EN bit in CDC_A_MICB_1_EN)
> 
> In theory, We should also disable the internal pull up here. if not we end
> up in two parallel resistors, effectively 1/2 the value of external
> resistor.
>

I think this should not happen in practice with this patch.

The internal pull up is a separate DAPM supply with my changes.
As such, the ASoC core will disable it whenever it is not needed.

Therefore, the only way to trigger this situation is to specifically
craft broken DAPM routes in the device tree, e.g.

	qcom,audio-routing =
		"AMIC1", "MIC BIAS Internal1",
		"AMIC1", "MIC BIAS External1";

Which is obviously wrong, because you should select either Internal1
*or* External1, depending on your board design.

> 
> 
> > 
> > Right now we have:
> >    SND_SOC_DAPM_SUPPLY("MIC BIAS Internal1", CDC_A_MICB_1_EN, 7, 0, ...) // I1
> >    SND_SOC_DAPM_SUPPLY("MIC BIAS External1", CDC_A_MICB_1_EN, 7, 0, ...) // E1
> > 
> > I2 is done in the PM event handler (pm8916_wcd_analog_enable_micbias_int1).
> > 
> > The idea of this patch is to simplify this, and use one DAPM supply
> > that handles the common (I1/E1), and one DAPM supply that handles (I2).
> > 
> > Translated to code we get:
> >    SND_SOC_DAPM_SUPPLY("MIC BIAS1", CDC_A_MICB_1_EN, 7, 0, ...) // I1/E1
> >    SND_SOC_DAPM_SUPPLY("MIC BIAS Internal1", CDC_A_MICB_1_INT_RBIAS, 7, 0, ...) // I2
> >    SND_SOC_DAPM_SUPPLY("MIC BIAS External1", SND_SOC_NOPM, ...) // dummy
> > 
> > And the routes:
> >    {"MIC BIAS Internal1", NULL, "MIC BIAS1"} // If I2, also do I1
> >    {"MIC BIAS External1", NULL, "MIC BIAS1"} // Only do E1
> 
> This should work! and makes it much clear too.
> 

I will submit a v2 with this setup. I think I simplified it a bit too
much in this patch.

> 
> > 
> > As you can see, for "MIC BIAS External1" we just do "MIC BIAS1".
> > The confusing element of this patch might be that I simplified it a bit
> > further and combined "MIC BIAS1" with "MIC BIAS External1".
> > This works because we don't do anything extra for "MIC BIAS External1".
> Should we not make sure that internal resistor switch is disabled here?
> 

See above. (I don't mind sending a v3 if we decide that we really need to
disable the internal rbias explicitly.)

> --srini
> 
> > 
> > Does that make sense?
> > 
> > Thanks for taking the time to review all my patches.
> > Stephan
> > 
> > > 
> > > --srini
> > > 
> > > 
> > > 
> > > 
> > > > 
> > > > This means that we can simplify the code by modelling MIC BIAS InternalX
> > > > as supply connected to MIC BIAS ExternalX. MIC BIAS InternalX is only
> > > > responsible for enabling the internal RBIAS resistor (2). The DAPM enable
> > > > sequence will automatically enable MIC BIAS ExternalX (1).
> > > > 
> > > > This makes it much easier to add support for MIC BIAS Internal3
> > > > as a next step.
> > > > 
> > > > Tested-by: Nikita Travkin <nikitos.tr@gmail.com> # longcheer-l8150
> > > > Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> > > > Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
> > > > ---
> > > >    sound/soc/codecs/msm8916-wcd-analog.c | 57 ++++++---------------------
> > > >    1 file changed, 13 insertions(+), 44 deletions(-)
> > > > 
> > > > diff --git a/sound/soc/codecs/msm8916-wcd-analog.c b/sound/soc/codecs/msm8916-wcd-analog.c
> > > > index 1f7964beb20c..930baae6eff5 100644
> > > > --- a/sound/soc/codecs/msm8916-wcd-analog.c
> > > > +++ b/sound/soc/codecs/msm8916-wcd-analog.c
> > > > @@ -389,23 +389,17 @@ static int pm8916_wcd_analog_enable_micbias_ext(struct snd_soc_component
> > > >    	return 0;
> > > >    }
> > > > -static int pm8916_wcd_analog_enable_micbias_int(struct snd_soc_component
> > > > -						 *component, int event,
> > > > -						 int reg, u32 cap_mode)
> > > > +static int pm8916_wcd_analog_enable_micbias_int(struct snd_soc_dapm_widget *w,
> > > > +						struct snd_kcontrol *kcontrol,
> > > > +						int event)
> > > >    {
> > > > +	struct snd_soc_component *component = snd_soc_dapm_to_component(w->dapm);
> > > >    	switch (event) {
> > > >    	case SND_SOC_DAPM_PRE_PMU:
> > > > -		snd_soc_component_update_bits(component, reg, MICB_1_EN_PULL_DOWN_EN_MASK, 0);
> > > >    		snd_soc_component_update_bits(component, CDC_A_MICB_1_EN,
> > > >    				    MICB_1_EN_OPA_STG2_TAIL_CURR_MASK,
> > > >    				    MICB_1_EN_OPA_STG2_TAIL_CURR_1_60UA);
> > > > -
> > > > -		break;
> > > > -	case SND_SOC_DAPM_POST_PMU:
> > > > -		pm8916_wcd_analog_micbias_enable(component);
> > > > -		snd_soc_component_update_bits(component, CDC_A_MICB_1_EN,
> > > > -				    MICB_1_EN_BYP_CAP_MASK, cap_mode);
> > > >    		break;
> > > >    	}
> > > > @@ -437,26 +431,6 @@ static int pm8916_wcd_analog_enable_micbias_ext2(struct
> > > >    }
> > > > -static int pm8916_wcd_analog_enable_micbias_int1(struct
> > > > -						  snd_soc_dapm_widget
> > > > -						  *w, struct snd_kcontrol
> > > > -						  *kcontrol, int event)
> > > > -{
> > > > -	struct snd_soc_component *component = snd_soc_dapm_to_component(w->dapm);
> > > > -	struct pm8916_wcd_analog_priv *wcd = snd_soc_component_get_drvdata(component);
> > > > -
> > > > -	switch (event) {
> > > > -	case SND_SOC_DAPM_PRE_PMU:
> > > > -		snd_soc_component_update_bits(component, CDC_A_MICB_1_INT_RBIAS,
> > > > -				    MICB_1_INT_TX1_INT_RBIAS_EN_MASK,
> > > > -				    MICB_1_INT_TX1_INT_RBIAS_EN_ENABLE);
> > > > -		break;
> > > > -	}
> > > > -
> > > > -	return pm8916_wcd_analog_enable_micbias_int(component, event, w->reg,
> > > > -						     wcd->micbias1_cap_mode);
> > > > -}
> > > > -
> > > >    static int pm8916_mbhc_configure_bias(struct pm8916_wcd_analog_priv *priv,
> > > >    				      bool micbias2_enabled)
> > > >    {
> > > > @@ -564,9 +538,8 @@ static int pm8916_wcd_analog_enable_micbias_int2(struct
> > > >    	switch (event) {
> > > >    	case SND_SOC_DAPM_PRE_PMU:
> > > > -		snd_soc_component_update_bits(component, CDC_A_MICB_1_INT_RBIAS,
> > > > -				    MICB_1_INT_TX2_INT_RBIAS_EN_MASK,
> > > > -				    MICB_1_INT_TX2_INT_RBIAS_EN_ENABLE);
> > > > +		snd_soc_component_update_bits(component, CDC_A_MICB_2_EN,
> > > > +					      CDC_A_MICB_2_PULL_DOWN_EN_MASK, 0);
> > > >    		break;
> > > >    	case SND_SOC_DAPM_POST_PMU:
> > > >    		pm8916_mbhc_configure_bias(wcd, true);
> > > > @@ -576,8 +549,7 @@ static int pm8916_wcd_analog_enable_micbias_int2(struct
> > > >    		break;
> > > >    	}
> > > > -	return pm8916_wcd_analog_enable_micbias_int(component, event, w->reg,
> > > > -						     wcd->micbias2_cap_mode);
> > > > +	return pm8916_wcd_analog_enable_micbias_int(w, kcontrol, event);
> > > >    }
> > > >    static int pm8916_wcd_analog_enable_adc(struct snd_soc_dapm_widget *w,
> > > > @@ -878,12 +850,10 @@ static const struct snd_soc_dapm_route pm8916_wcd_analog_audio_map[] = {
> > > >    	{"SPK PA", NULL, "SPK DAC"},
> > > >    	{"SPK DAC", "Switch", "PDM_RX3"},
> > > > -	{"MIC BIAS Internal1", NULL, "INT_LDO_H"},
> > > > -	{"MIC BIAS Internal2", NULL, "INT_LDO_H"},
> > > > +	{"MIC BIAS Internal1", NULL, "MIC BIAS External1"},
> > > > +	{"MIC BIAS Internal2", NULL, "MIC BIAS External2"},
> > > >    	{"MIC BIAS External1", NULL, "INT_LDO_H"},
> > > >    	{"MIC BIAS External2", NULL, "INT_LDO_H"},
> > > > -	{"MIC BIAS Internal1", NULL, "vdd-micbias"},
> > > > -	{"MIC BIAS Internal2", NULL, "vdd-micbias"},
> > > >    	{"MIC BIAS External1", NULL, "vdd-micbias"},
> > > >    	{"MIC BIAS External2", NULL, "vdd-micbias"},
> > > >    };
> > > > @@ -937,11 +907,10 @@ static const struct snd_soc_dapm_widget pm8916_wcd_analog_dapm_widgets[] = {
> > > >    	SND_SOC_DAPM_SUPPLY("RX_BIAS", CDC_A_RX_COM_BIAS_DAC, 7, 0, NULL, 0),
> > > >    	/* TX */
> > > > -	SND_SOC_DAPM_SUPPLY("MIC BIAS Internal1", CDC_A_MICB_1_EN, 7, 0,
> > > > -			    pm8916_wcd_analog_enable_micbias_int1,
> > > > -			    SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_POST_PMU |
> > > > -			    SND_SOC_DAPM_POST_PMD),
> > > > -	SND_SOC_DAPM_SUPPLY("MIC BIAS Internal2", CDC_A_MICB_2_EN, 7, 0,
> > > > +	SND_SOC_DAPM_SUPPLY("MIC BIAS Internal1", CDC_A_MICB_1_INT_RBIAS, 7, 0,
> > > > +			    pm8916_wcd_analog_enable_micbias_int,
> > > > +			    SND_SOC_DAPM_PRE_PMU),
> > > > +	SND_SOC_DAPM_SUPPLY("MIC BIAS Internal2", CDC_A_MICB_1_INT_RBIAS, 4, 0,
> > > >    			    pm8916_wcd_analog_enable_micbias_int2,
> > > >    			    SND_SOC_DAPM_PRE_PMU | SND_SOC_DAPM_POST_PMU |
> > > >    			    SND_SOC_DAPM_POST_PMD),
> > > > 
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