[PATCH 0/2] arm64: dts: qcom: Drop duplicate DMIC supplies for X13S/CRD

[PATCH 0/2] arm64: dts: qcom: Drop duplicate DMIC supplies for X13S/CRD

[Stephan Gerhold]

Drop the duplicated MIC BIAS supplies in "audio-routing" for the ThinkPad
X13S and the X1E80100. "MIC BIASn" and "VA MIC BIASn" are mutually
exclusive, only one of them can be active at the same time.

Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
---
Stephan Gerhold (2):
      arm64: dts: qcom: sc8280xp-x13s: Drop duplicate DMIC supplies
      arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

 arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts | 3 ---
 arch/arm64/boot/dts/qcom/x1e80100-crd.dts                  | 4 ----
 2 files changed, 7 deletions(-)
---
base-commit: 12b080aaf4275c579c91106ed926044b4d5df0af
change-id: 20241203-x1e80100-va-mic-bias-bab3bd5a7c57

Best regards,
-- 
Stephan Gerhold <stephan.gerhold@linaro.org>

[PATCH 1/2] arm64: dts: qcom: sc8280xp-x13s: Drop duplicate DMIC supplies

[Stephan Gerhold]

The WCD938x codec provides two controls for each of the MIC_BIASn outputs:

 - "MIC BIASn" enables an internal regulator to generate the output
   with a configurable voltage (qcom,micbiasN-microvolt).

 - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
   regulator and directly outputs fixed 1.8V from the VDD_PX pin.
   This is intended for low-power VA (voice activation) use cases.

The audio-routing setup for the ThinkPad X13s currently specifies both
as power supplies for the DMICs, but only one of them can be active
at the same time. In practice, only the internal regulator is used
with the current setup because the driver prefers it over pull-up mode.

Make this more clear by dropping the redundant routes to the pull-up
"VA MIC BIASn" supply. There is no functional difference except that we
skip briefly switching to pull-up mode when shutting down the microphone.

Fixes: 2e498f35c385 ("arm64: dts: qcom: sc8280xp-x13s: fix va dmic dai links and routing")
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
---
 arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
index f3190f408f4b2c7ca9fe368d652d5d66bb3949af..0f1ebd869ce315bfed2c17ae90b2451b3892b96b 100644
--- a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
+++ b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
@@ -1202,9 +1202,6 @@ &sound {
 		"VA DMIC0", "MIC BIAS1",
 		"VA DMIC1", "MIC BIAS1",
 		"VA DMIC2", "MIC BIAS3",
-		"VA DMIC0", "VA MIC BIAS1",
-		"VA DMIC1", "VA MIC BIAS1",
-		"VA DMIC2", "VA MIC BIAS3",
 		"TX SWR_ADC1", "ADC2_OUTPUT";
 
 	wcd-playback-dai-link {

-- 
2.47.0

[PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Stephan Gerhold]

The WCD938x codec provides two controls for each of the MIC_BIASn outputs:

 - "MIC BIASn" enables an internal regulator to generate the output
   with a configurable voltage (qcom,micbiasN-microvolt).

 - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
   regulator and directly outputs fixed 1.8V from the VDD_PX pin.
   This is intended for low-power VA (voice activation) use cases.

The audio-routing setup for the X1E80100 CRD currently specifies both
as power supplies for the DMICs, but only one of them can be active
at the same time. In practice, only the internal regulator is used
with the current setup because the driver prefers it over pull-up mode.

Make this more clear by dropping the redundant routes to the pull-up
"VA MIC BIASn" supply. There is no functional difference except that we
skip briefly switching to pull-up mode when shutting down the microphone.

Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
---
 arch/arm64/boot/dts/qcom/x1e80100-crd.dts | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/x1e80100-crd.dts b/arch/arm64/boot/dts/qcom/x1e80100-crd.dts
index 39f9d9cdc10d8e79824b72288e2529536144fa9e..a4d8da81bb4468e03ba8a9d37efaae10f7a6b53e 100644
--- a/arch/arm64/boot/dts/qcom/x1e80100-crd.dts
+++ b/arch/arm64/boot/dts/qcom/x1e80100-crd.dts
@@ -188,10 +188,6 @@ sound {
 				"VA DMIC1", "MIC BIAS3",
 				"VA DMIC2", "MIC BIAS1",
 				"VA DMIC3", "MIC BIAS1",
-				"VA DMIC0", "VA MIC BIAS3",
-				"VA DMIC1", "VA MIC BIAS3",
-				"VA DMIC2", "VA MIC BIAS1",
-				"VA DMIC3", "VA MIC BIAS1",
 				"TX SWR_INPUT1", "ADC2_OUTPUT";
 
 		wcd-playback-dai-link {

-- 
2.47.0

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Krzysztof Kozlowski]

On 03/12/2024 18:44, Stephan Gerhold wrote:
> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> 
>  - "MIC BIASn" enables an internal regulator to generate the output
>    with a configurable voltage (qcom,micbiasN-microvolt).
> 
>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
>    This is intended for low-power VA (voice activation) use cases.
> 
> The audio-routing setup for the X1E80100 CRD currently specifies both
> as power supplies for the DMICs, but only one of them can be active
> at the same time. In practice, only the internal regulator is used
> with the current setup because the driver prefers it over pull-up mode.
> 
> Make this more clear by dropping the redundant routes to the pull-up
> "VA MIC BIASn" supply. There is no functional difference except that we
> skip briefly switching to pull-up mode when shutting down the microphone.
> 
> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")

If there is no functional difference and this is just redundant, then
there is nothing to fix, so drop the tag. But the point is that users
might want the low-power VA. You claim they don't want... sure, I am
fine with that but there is nothing to fix in such case.

> Signed-off-by: Stephan Gerhold <stephan.gerhold@linaro.org>
> ---
>  arch/arm64/boot/dts/qcom/x1e80100-crd.dts | 4 ----
>  1 file changed, 4 deletions(-)
> 



Best regards,
Krzysztof

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Stephan Gerhold]

On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
> On 03/12/2024 18:44, Stephan Gerhold wrote:
> > The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> > 
> >  - "MIC BIASn" enables an internal regulator to generate the output
> >    with a configurable voltage (qcom,micbiasN-microvolt).
> > 
> >  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
> >    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
> >    This is intended for low-power VA (voice activation) use cases.
> > 
> > The audio-routing setup for the X1E80100 CRD currently specifies both
> > as power supplies for the DMICs, but only one of them can be active
> > at the same time. In practice, only the internal regulator is used
> > with the current setup because the driver prefers it over pull-up mode.
> > 
> > Make this more clear by dropping the redundant routes to the pull-up
> > "VA MIC BIASn" supply. There is no functional difference except that we
> > skip briefly switching to pull-up mode when shutting down the microphone.
> > 
> > Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
> 
> If there is no functional difference and this is just redundant, then
> there is nothing to fix, so drop the tag. But the point is that users
> might want the low-power VA. You claim they don't want... sure, I am
> fine with that but there is nothing to fix in such case.
> 

The fix here is that two mutually exclusive power supplies for the DMIC
are specified in the device tree. You can only have one of them active
at the same time. The Linux driver handles that gracefully, but the
device tree is still wrong and IMO deserves a fixes tag.

The functional difference is that we skip briefly switching to pull-up
mode when shutting down the microphone. Users won't notice that, but
it's not the intended behavior.

I don't claim that users don't want to switch to the low-power pull-up
mode (VA MIC BIASn). However, we would need a different mechanism to
give them the option to switch at runtime. "audio-routing" just
specifies static routes, so the current description does not allow
switching between the two modes either.

Thanks,
Stephan

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Konrad Dybcio]

On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
> On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
>> On 03/12/2024 18:44, Stephan Gerhold wrote:
>>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
>>>
>>>  - "MIC BIASn" enables an internal regulator to generate the output
>>>    with a configurable voltage (qcom,micbiasN-microvolt).
>>>
>>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
>>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
>>>    This is intended for low-power VA (voice activation) use cases.
>>>
>>> The audio-routing setup for the X1E80100 CRD currently specifies both
>>> as power supplies for the DMICs, but only one of them can be active
>>> at the same time. In practice, only the internal regulator is used
>>> with the current setup because the driver prefers it over pull-up mode.
>>>
>>> Make this more clear by dropping the redundant routes to the pull-up
>>> "VA MIC BIASn" supply. There is no functional difference except that we
>>> skip briefly switching to pull-up mode when shutting down the microphone.
>>>
>>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
>>
>> If there is no functional difference and this is just redundant, then
>> there is nothing to fix, so drop the tag. But the point is that users
>> might want the low-power VA. You claim they don't want... sure, I am
>> fine with that but there is nothing to fix in such case.
>>
> 
> The fix here is that two mutually exclusive power supplies for the DMIC
> are specified in the device tree. You can only have one of them active
> at the same time. The Linux driver handles that gracefully, but the
> device tree is still wrong and IMO deserves a fixes tag.
> 
> The functional difference is that we skip briefly switching to pull-up
> mode when shutting down the microphone. Users won't notice that, but
> it's not the intended behavior.
> 
> I don't claim that users don't want to switch to the low-power pull-up
> mode (VA MIC BIASn). However, we would need a different mechanism to
> give them the option to switch at runtime. "audio-routing" just
> specifies static routes, so the current description does not allow
> switching between the two modes either.

Is there no existing mechanism to alter this at runtime?

Konrad

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Stephan Gerhold]

On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
> On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
> > On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
> >> On 03/12/2024 18:44, Stephan Gerhold wrote:
> >>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> >>>
> >>>  - "MIC BIASn" enables an internal regulator to generate the output
> >>>    with a configurable voltage (qcom,micbiasN-microvolt).
> >>>
> >>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
> >>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
> >>>    This is intended for low-power VA (voice activation) use cases.
> >>>
> >>> The audio-routing setup for the X1E80100 CRD currently specifies both
> >>> as power supplies for the DMICs, but only one of them can be active
> >>> at the same time. In practice, only the internal regulator is used
> >>> with the current setup because the driver prefers it over pull-up mode.
> >>>
> >>> Make this more clear by dropping the redundant routes to the pull-up
> >>> "VA MIC BIASn" supply. There is no functional difference except that we
> >>> skip briefly switching to pull-up mode when shutting down the microphone.
> >>>
> >>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
> >>
> >> If there is no functional difference and this is just redundant, then
> >> there is nothing to fix, so drop the tag. But the point is that users
> >> might want the low-power VA. You claim they don't want... sure, I am
> >> fine with that but there is nothing to fix in such case.
> >>
> > 
> > The fix here is that two mutually exclusive power supplies for the DMIC
> > are specified in the device tree. You can only have one of them active
> > at the same time. The Linux driver handles that gracefully, but the
> > device tree is still wrong and IMO deserves a fixes tag.
> > 
> > The functional difference is that we skip briefly switching to pull-up
> > mode when shutting down the microphone. Users won't notice that, but
> > it's not the intended behavior.
> > 
> > I don't claim that users don't want to switch to the low-power pull-up
> > mode (VA MIC BIASn). However, we would need a different mechanism to
> > give them the option to switch at runtime. "audio-routing" just
> > specifies static routes, so the current description does not allow
> > switching between the two modes either.
> 
> Is there no existing mechanism to alter this at runtime?
> 

I don't think so... Since it's currently exposed as two separate DAPM
supplies (instead of a mux or similar) you can only choose between one
of them in the static routes specified by "audio-routing" in the DT.

I tried looking at how downstream handles this, but this left me even
more confused than I was before. :-) On CRD we currently have the
following routes in DT:

	"VA DMIC0", "MIC BIAS3",
	"VA DMIC1", "MIC BIAS3",
	"VA DMIC2", "MIC BIAS1",
	"VA DMIC3", "MIC BIAS1",
	"VA DMIC0", "VA MIC BIAS3",
	"VA DMIC1", "VA MIC BIAS3",
	"VA DMIC2", "VA MIC BIAS1",
	"VA DMIC3", "VA MIC BIAS1",

MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
But if you look at e.g. SM8550 downstream they have:

	"TX DMIC0", "MIC BIAS3",
	"TX DMIC1", "MIC BIAS3",
	"TX DMIC2", "MIC BIAS1",
	"TX DMIC3", "MIC BIAS1",
	"VA DMIC0", "VA MIC BIAS3",
	"VA DMIC1", "VA MIC BIAS3",
	"VA DMIC2", "VA MIC BIAS1",
	"VA DMIC3", "VA MIC BIAS1";

Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
TX macro DMIC, and the low-power one for the VA macro DMIC. That would
be fine.

Now the question is: If we can use the DMIC through both the TX and the
VA macro, and we're not doing voice activation, why are we using the VA
macro in the first place?

@Srini: Do you remember why?

Thanks,
Stephan

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Bjorn Andersson]

On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
> On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
> > On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
> > > On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
> > >> On 03/12/2024 18:44, Stephan Gerhold wrote:
> > >>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> > >>>
> > >>>  - "MIC BIASn" enables an internal regulator to generate the output
> > >>>    with a configurable voltage (qcom,micbiasN-microvolt).
> > >>>
> > >>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
> > >>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
> > >>>    This is intended for low-power VA (voice activation) use cases.
> > >>>
> > >>> The audio-routing setup for the X1E80100 CRD currently specifies both
> > >>> as power supplies for the DMICs, but only one of them can be active
> > >>> at the same time. In practice, only the internal regulator is used
> > >>> with the current setup because the driver prefers it over pull-up mode.
> > >>>
> > >>> Make this more clear by dropping the redundant routes to the pull-up
> > >>> "VA MIC BIASn" supply. There is no functional difference except that we
> > >>> skip briefly switching to pull-up mode when shutting down the microphone.
> > >>>
> > >>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
> > >>
> > >> If there is no functional difference and this is just redundant, then
> > >> there is nothing to fix, so drop the tag. But the point is that users
> > >> might want the low-power VA. You claim they don't want... sure, I am
> > >> fine with that but there is nothing to fix in such case.
> > >>
> > > 
> > > The fix here is that two mutually exclusive power supplies for the DMIC
> > > are specified in the device tree. You can only have one of them active
> > > at the same time. The Linux driver handles that gracefully, but the
> > > device tree is still wrong and IMO deserves a fixes tag.
> > > 
> > > The functional difference is that we skip briefly switching to pull-up
> > > mode when shutting down the microphone. Users won't notice that, but
> > > it's not the intended behavior.
> > > 
> > > I don't claim that users don't want to switch to the low-power pull-up
> > > mode (VA MIC BIASn). However, we would need a different mechanism to
> > > give them the option to switch at runtime. "audio-routing" just
> > > specifies static routes, so the current description does not allow
> > > switching between the two modes either.
> > 
> > Is there no existing mechanism to alter this at runtime?
> > 
> 
> I don't think so... Since it's currently exposed as two separate DAPM
> supplies (instead of a mux or similar) you can only choose between one
> of them in the static routes specified by "audio-routing" in the DT.
> 
> I tried looking at how downstream handles this, but this left me even
> more confused than I was before. :-) On CRD we currently have the
> following routes in DT:
> 
> 	"VA DMIC0", "MIC BIAS3",
> 	"VA DMIC1", "MIC BIAS3",
> 	"VA DMIC2", "MIC BIAS1",
> 	"VA DMIC3", "MIC BIAS1",
> 	"VA DMIC0", "VA MIC BIAS3",
> 	"VA DMIC1", "VA MIC BIAS3",
> 	"VA DMIC2", "VA MIC BIAS1",
> 	"VA DMIC3", "VA MIC BIAS1",
> 
> MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
> But if you look at e.g. SM8550 downstream they have:
> 
> 	"TX DMIC0", "MIC BIAS3",
> 	"TX DMIC1", "MIC BIAS3",
> 	"TX DMIC2", "MIC BIAS1",
> 	"TX DMIC3", "MIC BIAS1",
> 	"VA DMIC0", "VA MIC BIAS3",
> 	"VA DMIC1", "VA MIC BIAS3",
> 	"VA DMIC2", "VA MIC BIAS1",
> 	"VA DMIC3", "VA MIC BIAS1";
> 
> Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
> TX macro DMIC, and the low-power one for the VA macro DMIC. That would
> be fine.
> 
> Now the question is: If we can use the DMIC through both the TX and the
> VA macro, and we're not doing voice activation, why are we using the VA
> macro in the first place?
> 
> @Srini: Do you remember why?
> 

What's the verdict regarding this?

Regards,
Bjorn

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Stephan Gerhold]

On Wed, Jan 08, 2025 at 05:07:47PM -0600, Bjorn Andersson wrote:
> On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
> > On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
> > > On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
> > > > On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
> > > >> On 03/12/2024 18:44, Stephan Gerhold wrote:
> > > >>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> > > >>>
> > > >>>  - "MIC BIASn" enables an internal regulator to generate the output
> > > >>>    with a configurable voltage (qcom,micbiasN-microvolt).
> > > >>>
> > > >>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
> > > >>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
> > > >>>    This is intended for low-power VA (voice activation) use cases.
> > > >>>
> > > >>> The audio-routing setup for the X1E80100 CRD currently specifies both
> > > >>> as power supplies for the DMICs, but only one of them can be active
> > > >>> at the same time. In practice, only the internal regulator is used
> > > >>> with the current setup because the driver prefers it over pull-up mode.
> > > >>>
> > > >>> Make this more clear by dropping the redundant routes to the pull-up
> > > >>> "VA MIC BIASn" supply. There is no functional difference except that we
> > > >>> skip briefly switching to pull-up mode when shutting down the microphone.
> > > >>>
> > > >>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
> > > >>
> > > >> If there is no functional difference and this is just redundant, then
> > > >> there is nothing to fix, so drop the tag. But the point is that users
> > > >> might want the low-power VA. You claim they don't want... sure, I am
> > > >> fine with that but there is nothing to fix in such case.
> > > >>
> > > > 
> > > > The fix here is that two mutually exclusive power supplies for the DMIC
> > > > are specified in the device tree. You can only have one of them active
> > > > at the same time. The Linux driver handles that gracefully, but the
> > > > device tree is still wrong and IMO deserves a fixes tag.
> > > > 
> > > > The functional difference is that we skip briefly switching to pull-up
> > > > mode when shutting down the microphone. Users won't notice that, but
> > > > it's not the intended behavior.
> > > > 
> > > > I don't claim that users don't want to switch to the low-power pull-up
> > > > mode (VA MIC BIASn). However, we would need a different mechanism to
> > > > give them the option to switch at runtime. "audio-routing" just
> > > > specifies static routes, so the current description does not allow
> > > > switching between the two modes either.
> > > 
> > > Is there no existing mechanism to alter this at runtime?
> > > 
> > 
> > I don't think so... Since it's currently exposed as two separate DAPM
> > supplies (instead of a mux or similar) you can only choose between one
> > of them in the static routes specified by "audio-routing" in the DT.
> > 
> > I tried looking at how downstream handles this, but this left me even
> > more confused than I was before. :-) On CRD we currently have the
> > following routes in DT:
> > 
> > 	"VA DMIC0", "MIC BIAS3",
> > 	"VA DMIC1", "MIC BIAS3",
> > 	"VA DMIC2", "MIC BIAS1",
> > 	"VA DMIC3", "MIC BIAS1",
> > 	"VA DMIC0", "VA MIC BIAS3",
> > 	"VA DMIC1", "VA MIC BIAS3",
> > 	"VA DMIC2", "VA MIC BIAS1",
> > 	"VA DMIC3", "VA MIC BIAS1",
> > 
> > MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
> > But if you look at e.g. SM8550 downstream they have:
> > 
> > 	"TX DMIC0", "MIC BIAS3",
> > 	"TX DMIC1", "MIC BIAS3",
> > 	"TX DMIC2", "MIC BIAS1",
> > 	"TX DMIC3", "MIC BIAS1",
> > 	"VA DMIC0", "VA MIC BIAS3",
> > 	"VA DMIC1", "VA MIC BIAS3",
> > 	"VA DMIC2", "VA MIC BIAS1",
> > 	"VA DMIC3", "VA MIC BIAS1";
> > 
> > Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
> > TX macro DMIC, and the low-power one for the VA macro DMIC. That would
> > be fine.
> > 
> > Now the question is: If we can use the DMIC through both the TX and the
> > VA macro, and we're not doing voice activation, why are we using the VA
> > macro in the first place?
> > 
> > @Srini: Do you remember why?
> > 
> 
> What's the verdict regarding this?
> 

We started discussing this, but did not come to a conclusion yet if we
should be recording from the DMICs using the TX macro instead of the VA
macro.

The patch I submitted is still valid though, independent of that
question. Since we're not doing voice activation we want to have the
"full quality" MIC BIAS supply, not the low-power one.

It looks like there have been new users of this pattern added upstream.
I'll resend this patch with all the new occurrences and will try further
clarifying the commit messge while at it.

Thanks,
Stephan

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Konrad Dybcio]

On 9.01.2025 10:32 AM, Stephan Gerhold wrote:
> On Wed, Jan 08, 2025 at 05:07:47PM -0600, Bjorn Andersson wrote:
>> On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
>>> On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
>>>> On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
>>>>> On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
>>>>>> On 03/12/2024 18:44, Stephan Gerhold wrote:
>>>>>>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
>>>>>>>
>>>>>>>  - "MIC BIASn" enables an internal regulator to generate the output
>>>>>>>    with a configurable voltage (qcom,micbiasN-microvolt).
>>>>>>>
>>>>>>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
>>>>>>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
>>>>>>>    This is intended for low-power VA (voice activation) use cases.
>>>>>>>
>>>>>>> The audio-routing setup for the X1E80100 CRD currently specifies both
>>>>>>> as power supplies for the DMICs, but only one of them can be active
>>>>>>> at the same time. In practice, only the internal regulator is used
>>>>>>> with the current setup because the driver prefers it over pull-up mode.
>>>>>>>
>>>>>>> Make this more clear by dropping the redundant routes to the pull-up
>>>>>>> "VA MIC BIASn" supply. There is no functional difference except that we
>>>>>>> skip briefly switching to pull-up mode when shutting down the microphone.
>>>>>>>
>>>>>>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
>>>>>>
>>>>>> If there is no functional difference and this is just redundant, then
>>>>>> there is nothing to fix, so drop the tag. But the point is that users
>>>>>> might want the low-power VA. You claim they don't want... sure, I am
>>>>>> fine with that but there is nothing to fix in such case.
>>>>>>
>>>>>
>>>>> The fix here is that two mutually exclusive power supplies for the DMIC
>>>>> are specified in the device tree. You can only have one of them active
>>>>> at the same time. The Linux driver handles that gracefully, but the
>>>>> device tree is still wrong and IMO deserves a fixes tag.
>>>>>
>>>>> The functional difference is that we skip briefly switching to pull-up
>>>>> mode when shutting down the microphone. Users won't notice that, but
>>>>> it's not the intended behavior.
>>>>>
>>>>> I don't claim that users don't want to switch to the low-power pull-up
>>>>> mode (VA MIC BIASn). However, we would need a different mechanism to
>>>>> give them the option to switch at runtime. "audio-routing" just
>>>>> specifies static routes, so the current description does not allow
>>>>> switching between the two modes either.
>>>>
>>>> Is there no existing mechanism to alter this at runtime?
>>>>
>>>
>>> I don't think so... Since it's currently exposed as two separate DAPM
>>> supplies (instead of a mux or similar) you can only choose between one
>>> of them in the static routes specified by "audio-routing" in the DT.
>>>
>>> I tried looking at how downstream handles this, but this left me even
>>> more confused than I was before. :-) On CRD we currently have the
>>> following routes in DT:
>>>
>>> 	"VA DMIC0", "MIC BIAS3",
>>> 	"VA DMIC1", "MIC BIAS3",
>>> 	"VA DMIC2", "MIC BIAS1",
>>> 	"VA DMIC3", "MIC BIAS1",
>>> 	"VA DMIC0", "VA MIC BIAS3",
>>> 	"VA DMIC1", "VA MIC BIAS3",
>>> 	"VA DMIC2", "VA MIC BIAS1",
>>> 	"VA DMIC3", "VA MIC BIAS1",
>>>
>>> MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
>>> But if you look at e.g. SM8550 downstream they have:
>>>
>>> 	"TX DMIC0", "MIC BIAS3",
>>> 	"TX DMIC1", "MIC BIAS3",
>>> 	"TX DMIC2", "MIC BIAS1",
>>> 	"TX DMIC3", "MIC BIAS1",
>>> 	"VA DMIC0", "VA MIC BIAS3",
>>> 	"VA DMIC1", "VA MIC BIAS3",
>>> 	"VA DMIC2", "VA MIC BIAS1",
>>> 	"VA DMIC3", "VA MIC BIAS1";
>>>
>>> Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
>>> TX macro DMIC, and the low-power one for the VA macro DMIC. That would
>>> be fine.
>>>
>>> Now the question is: If we can use the DMIC through both the TX and the
>>> VA macro, and we're not doing voice activation, why are we using the VA
>>> macro in the first place?
>>>
>>> @Srini: Do you remember why?
>>>
>>
>> What's the verdict regarding this?
>>
> 
> We started discussing this, but did not come to a conclusion yet if we
> should be recording from the DMICs using the TX macro instead of the VA
> macro.
> 
> The patch I submitted is still valid though, independent of that
> question. Since we're not doing voice activation we want to have the
> "full quality" MIC BIAS supply, not the low-power one.

Can/should we discuss a new sound API to make this toggleable?

Do these microphones physically connect to muxable inputs, or does this
depend on board wiring?

Konrad

> 
> It looks like there have been new users of this pattern added upstream.
> I'll resend this patch with all the new occurrences and will try further
> clarifying the commit messge while at it.
> 
> Thanks,
> Stephan

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Stephan Gerhold]

On Thu, Jan 09, 2025 at 01:57:17PM +0100, Konrad Dybcio wrote:
> On 9.01.2025 10:32 AM, Stephan Gerhold wrote:
> > On Wed, Jan 08, 2025 at 05:07:47PM -0600, Bjorn Andersson wrote:
> >> On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
> >>> On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
> >>>> On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
> >>>>> On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
> >>>>>> On 03/12/2024 18:44, Stephan Gerhold wrote:
> >>>>>>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> >>>>>>>
> >>>>>>>  - "MIC BIASn" enables an internal regulator to generate the output
> >>>>>>>    with a configurable voltage (qcom,micbiasN-microvolt).
> >>>>>>>
> >>>>>>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
> >>>>>>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
> >>>>>>>    This is intended for low-power VA (voice activation) use cases.
> >>>>>>>
> >>>>>>> The audio-routing setup for the X1E80100 CRD currently specifies both
> >>>>>>> as power supplies for the DMICs, but only one of them can be active
> >>>>>>> at the same time. In practice, only the internal regulator is used
> >>>>>>> with the current setup because the driver prefers it over pull-up mode.
> >>>>>>>
> >>>>>>> Make this more clear by dropping the redundant routes to the pull-up
> >>>>>>> "VA MIC BIASn" supply. There is no functional difference except that we
> >>>>>>> skip briefly switching to pull-up mode when shutting down the microphone.
> >>>>>>>
> >>>>>>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
> >>>>>>
> >>>>>> If there is no functional difference and this is just redundant, then
> >>>>>> there is nothing to fix, so drop the tag. But the point is that users
> >>>>>> might want the low-power VA. You claim they don't want... sure, I am
> >>>>>> fine with that but there is nothing to fix in such case.
> >>>>>>
> >>>>>
> >>>>> The fix here is that two mutually exclusive power supplies for the DMIC
> >>>>> are specified in the device tree. You can only have one of them active
> >>>>> at the same time. The Linux driver handles that gracefully, but the
> >>>>> device tree is still wrong and IMO deserves a fixes tag.
> >>>>>
> >>>>> The functional difference is that we skip briefly switching to pull-up
> >>>>> mode when shutting down the microphone. Users won't notice that, but
> >>>>> it's not the intended behavior.
> >>>>>
> >>>>> I don't claim that users don't want to switch to the low-power pull-up
> >>>>> mode (VA MIC BIASn). However, we would need a different mechanism to
> >>>>> give them the option to switch at runtime. "audio-routing" just
> >>>>> specifies static routes, so the current description does not allow
> >>>>> switching between the two modes either.
> >>>>
> >>>> Is there no existing mechanism to alter this at runtime?
> >>>>
> >>>
> >>> I don't think so... Since it's currently exposed as two separate DAPM
> >>> supplies (instead of a mux or similar) you can only choose between one
> >>> of them in the static routes specified by "audio-routing" in the DT.
> >>>
> >>> I tried looking at how downstream handles this, but this left me even
> >>> more confused than I was before. :-) On CRD we currently have the
> >>> following routes in DT:
> >>>
> >>> 	"VA DMIC0", "MIC BIAS3",
> >>> 	"VA DMIC1", "MIC BIAS3",
> >>> 	"VA DMIC2", "MIC BIAS1",
> >>> 	"VA DMIC3", "MIC BIAS1",
> >>> 	"VA DMIC0", "VA MIC BIAS3",
> >>> 	"VA DMIC1", "VA MIC BIAS3",
> >>> 	"VA DMIC2", "VA MIC BIAS1",
> >>> 	"VA DMIC3", "VA MIC BIAS1",
> >>>
> >>> MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
> >>> But if you look at e.g. SM8550 downstream they have:
> >>>
> >>> 	"TX DMIC0", "MIC BIAS3",
> >>> 	"TX DMIC1", "MIC BIAS3",
> >>> 	"TX DMIC2", "MIC BIAS1",
> >>> 	"TX DMIC3", "MIC BIAS1",
> >>> 	"VA DMIC0", "VA MIC BIAS3",
> >>> 	"VA DMIC1", "VA MIC BIAS3",
> >>> 	"VA DMIC2", "VA MIC BIAS1",
> >>> 	"VA DMIC3", "VA MIC BIAS1";
> >>>
> >>> Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
> >>> TX macro DMIC, and the low-power one for the VA macro DMIC. That would
> >>> be fine.
> >>>
> >>> Now the question is: If we can use the DMIC through both the TX and the
> >>> VA macro, and we're not doing voice activation, why are we using the VA
> >>> macro in the first place?
> >>>
> >>> @Srini: Do you remember why?
> >>>
> >>
> >> What's the verdict regarding this?
> >>
> > 
> > We started discussing this, but did not come to a conclusion yet if we
> > should be recording from the DMICs using the TX macro instead of the VA
> > macro.
> > 
> > The patch I submitted is still valid though, independent of that
> > question. Since we're not doing voice activation we want to have the
> > "full quality" MIC BIAS supply, not the low-power one.
> 
> Can/should we discuss a new sound API to make this toggleable?
> 
> Do these microphones physically connect to muxable inputs, or does this
> depend on board wiring?
> 

The WCD938x codec has 4 MIC_BIAS output pins that are typically used as
power supply for microphones. Inside the codec there is an option to
drive these output pins in one of two modes:

 1. Internal regulator to generate the output with a configurable
    voltage (qcom,micbiasN-microvolt). Exposed as "MIC BIASn" supply in
    the Linux driver.

 2. "Pull-up mode" that bypasses the internal regulator and directly
    outputs fixed 1.8V from the VDD_PX pin. Exposed as "VA MIC BIASn"
    supply in the Linux driver.

The board-specific part here is only which microphone is wired to which
MIC BIAS pin (e.g. DMIC0 -> MIC BIAS3, DMIC2 -> MIC BIAS1 etc). 

Both options will work if the microphone can operate at 1.8V. In that
case, I think generally we want (1) for normal audio use cases and (2)
for low-power use cases (like "voice activation").

Apparently the same applies for the "macro" to use. TX macro should be
used for normal audio, and VA macro only for low-power use cases. With
that there is a clear mapping:

 - TX macro DMICs -> full power "MIC BIAS" supply
 - VA macro DMICs -> low-power "VA MIC BIAS" supply

I don't see why someone would want to change this mapping, so I don't
think it's worth making this user configurable.

Given that we're currently using the VA macro for normal audio, we
should describe VA macro DMICs -> full power "MIC BIAS" supply for now
and ideally migrate to using the TX macro later.

Thanks,
Stephan

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Konrad Dybcio]

On 9.01.2025 2:29 PM, Stephan Gerhold wrote:
> On Thu, Jan 09, 2025 at 01:57:17PM +0100, Konrad Dybcio wrote:
>> On 9.01.2025 10:32 AM, Stephan Gerhold wrote:
>>> On Wed, Jan 08, 2025 at 05:07:47PM -0600, Bjorn Andersson wrote:
>>>> On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
>>>>> On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
>>>>>> On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
>>>>>>> On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
>>>>>>>> On 03/12/2024 18:44, Stephan Gerhold wrote:
>>>>>>>>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
>>>>>>>>>
>>>>>>>>>  - "MIC BIASn" enables an internal regulator to generate the output
>>>>>>>>>    with a configurable voltage (qcom,micbiasN-microvolt).
>>>>>>>>>
>>>>>>>>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
>>>>>>>>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
>>>>>>>>>    This is intended for low-power VA (voice activation) use cases.
>>>>>>>>>
>>>>>>>>> The audio-routing setup for the X1E80100 CRD currently specifies both
>>>>>>>>> as power supplies for the DMICs, but only one of them can be active
>>>>>>>>> at the same time. In practice, only the internal regulator is used
>>>>>>>>> with the current setup because the driver prefers it over pull-up mode.
>>>>>>>>>
>>>>>>>>> Make this more clear by dropping the redundant routes to the pull-up
>>>>>>>>> "VA MIC BIASn" supply. There is no functional difference except that we
>>>>>>>>> skip briefly switching to pull-up mode when shutting down the microphone.
>>>>>>>>>
>>>>>>>>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
>>>>>>>>
>>>>>>>> If there is no functional difference and this is just redundant, then
>>>>>>>> there is nothing to fix, so drop the tag. But the point is that users
>>>>>>>> might want the low-power VA. You claim they don't want... sure, I am
>>>>>>>> fine with that but there is nothing to fix in such case.
>>>>>>>>
>>>>>>>
>>>>>>> The fix here is that two mutually exclusive power supplies for the DMIC
>>>>>>> are specified in the device tree. You can only have one of them active
>>>>>>> at the same time. The Linux driver handles that gracefully, but the
>>>>>>> device tree is still wrong and IMO deserves a fixes tag.
>>>>>>>
>>>>>>> The functional difference is that we skip briefly switching to pull-up
>>>>>>> mode when shutting down the microphone. Users won't notice that, but
>>>>>>> it's not the intended behavior.
>>>>>>>
>>>>>>> I don't claim that users don't want to switch to the low-power pull-up
>>>>>>> mode (VA MIC BIASn). However, we would need a different mechanism to
>>>>>>> give them the option to switch at runtime. "audio-routing" just
>>>>>>> specifies static routes, so the current description does not allow
>>>>>>> switching between the two modes either.
>>>>>>
>>>>>> Is there no existing mechanism to alter this at runtime?
>>>>>>
>>>>>
>>>>> I don't think so... Since it's currently exposed as two separate DAPM
>>>>> supplies (instead of a mux or similar) you can only choose between one
>>>>> of them in the static routes specified by "audio-routing" in the DT.
>>>>>
>>>>> I tried looking at how downstream handles this, but this left me even
>>>>> more confused than I was before. :-) On CRD we currently have the
>>>>> following routes in DT:
>>>>>
>>>>> 	"VA DMIC0", "MIC BIAS3",
>>>>> 	"VA DMIC1", "MIC BIAS3",
>>>>> 	"VA DMIC2", "MIC BIAS1",
>>>>> 	"VA DMIC3", "MIC BIAS1",
>>>>> 	"VA DMIC0", "VA MIC BIAS3",
>>>>> 	"VA DMIC1", "VA MIC BIAS3",
>>>>> 	"VA DMIC2", "VA MIC BIAS1",
>>>>> 	"VA DMIC3", "VA MIC BIAS1",
>>>>>
>>>>> MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
>>>>> But if you look at e.g. SM8550 downstream they have:
>>>>>
>>>>> 	"TX DMIC0", "MIC BIAS3",
>>>>> 	"TX DMIC1", "MIC BIAS3",
>>>>> 	"TX DMIC2", "MIC BIAS1",
>>>>> 	"TX DMIC3", "MIC BIAS1",
>>>>> 	"VA DMIC0", "VA MIC BIAS3",
>>>>> 	"VA DMIC1", "VA MIC BIAS3",
>>>>> 	"VA DMIC2", "VA MIC BIAS1",
>>>>> 	"VA DMIC3", "VA MIC BIAS1";
>>>>>
>>>>> Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
>>>>> TX macro DMIC, and the low-power one for the VA macro DMIC. That would
>>>>> be fine.
>>>>>
>>>>> Now the question is: If we can use the DMIC through both the TX and the
>>>>> VA macro, and we're not doing voice activation, why are we using the VA
>>>>> macro in the first place?
>>>>>
>>>>> @Srini: Do you remember why?
>>>>>
>>>>
>>>> What's the verdict regarding this?
>>>>
>>>
>>> We started discussing this, but did not come to a conclusion yet if we
>>> should be recording from the DMICs using the TX macro instead of the VA
>>> macro.
>>>
>>> The patch I submitted is still valid though, independent of that
>>> question. Since we're not doing voice activation we want to have the
>>> "full quality" MIC BIAS supply, not the low-power one.
>>
>> Can/should we discuss a new sound API to make this toggleable?
>>
>> Do these microphones physically connect to muxable inputs, or does this
>> depend on board wiring?
>>
> 
> The WCD938x codec has 4 MIC_BIAS output pins that are typically used as
> power supply for microphones. Inside the codec there is an option to
> drive these output pins in one of two modes:
> 
>  1. Internal regulator to generate the output with a configurable
>     voltage (qcom,micbiasN-microvolt). Exposed as "MIC BIASn" supply in
>     the Linux driver.
> 
>  2. "Pull-up mode" that bypasses the internal regulator and directly
>     outputs fixed 1.8V from the VDD_PX pin. Exposed as "VA MIC BIASn"
>     supply in the Linux driver.
> 
> The board-specific part here is only which microphone is wired to which
> MIC BIAS pin (e.g. DMIC0 -> MIC BIAS3, DMIC2 -> MIC BIAS1 etc). 
> 
> Both options will work if the microphone can operate at 1.8V. In that
> case, I think generally we want (1) for normal audio use cases and (2)
> for low-power use cases (like "voice activation").
> 
> Apparently the same applies for the "macro" to use. TX macro should be
> used for normal audio, and VA macro only for low-power use cases. With
> that there is a clear mapping:
> 
>  - TX macro DMICs -> full power "MIC BIAS" supply
>  - VA macro DMICs -> low-power "VA MIC BIAS" supply
> 
> I don't see why someone would want to change this mapping, so I don't
> think it's worth making this user configurable.
> 
> Given that we're currently using the VA macro for normal audio, we
> should describe VA macro DMICs -> full power "MIC BIAS" supply for now
> and ideally migrate to using the TX macro later.

So, in short, if I understood you correctly, audio comes in through a
hardwired connection to a given macro, but the bias pins can be configured
to output the bias voltage through any of the macros.

In that case, I agree only keeping the one matching the macro the mics
are connected to is the solution here

Konrad

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Stephan Gerhold]

On Thu, Jan 09, 2025 at 03:00:01PM +0100, Konrad Dybcio wrote:
> On 9.01.2025 2:29 PM, Stephan Gerhold wrote:
> > On Thu, Jan 09, 2025 at 01:57:17PM +0100, Konrad Dybcio wrote:
> >> On 9.01.2025 10:32 AM, Stephan Gerhold wrote:
> >>> On Wed, Jan 08, 2025 at 05:07:47PM -0600, Bjorn Andersson wrote:
> >>>> On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
> >>>>> On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
> >>>>>> On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
> >>>>>>> On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
> >>>>>>>> On 03/12/2024 18:44, Stephan Gerhold wrote:
> >>>>>>>>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> >>>>>>>>>
> >>>>>>>>>  - "MIC BIASn" enables an internal regulator to generate the output
> >>>>>>>>>    with a configurable voltage (qcom,micbiasN-microvolt).
> >>>>>>>>>
> >>>>>>>>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
> >>>>>>>>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
> >>>>>>>>>    This is intended for low-power VA (voice activation) use cases.
> >>>>>>>>>
> >>>>>>>>> The audio-routing setup for the X1E80100 CRD currently specifies both
> >>>>>>>>> as power supplies for the DMICs, but only one of them can be active
> >>>>>>>>> at the same time. In practice, only the internal regulator is used
> >>>>>>>>> with the current setup because the driver prefers it over pull-up mode.
> >>>>>>>>>
> >>>>>>>>> Make this more clear by dropping the redundant routes to the pull-up
> >>>>>>>>> "VA MIC BIASn" supply. There is no functional difference except that we
> >>>>>>>>> skip briefly switching to pull-up mode when shutting down the microphone.
> >>>>>>>>>
> >>>>>>>>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
> >>>>>>>>
> >>>>>>>> If there is no functional difference and this is just redundant, then
> >>>>>>>> there is nothing to fix, so drop the tag. But the point is that users
> >>>>>>>> might want the low-power VA. You claim they don't want... sure, I am
> >>>>>>>> fine with that but there is nothing to fix in such case.
> >>>>>>>>
> >>>>>>>
> >>>>>>> The fix here is that two mutually exclusive power supplies for the DMIC
> >>>>>>> are specified in the device tree. You can only have one of them active
> >>>>>>> at the same time. The Linux driver handles that gracefully, but the
> >>>>>>> device tree is still wrong and IMO deserves a fixes tag.
> >>>>>>>
> >>>>>>> The functional difference is that we skip briefly switching to pull-up
> >>>>>>> mode when shutting down the microphone. Users won't notice that, but
> >>>>>>> it's not the intended behavior.
> >>>>>>>
> >>>>>>> I don't claim that users don't want to switch to the low-power pull-up
> >>>>>>> mode (VA MIC BIASn). However, we would need a different mechanism to
> >>>>>>> give them the option to switch at runtime. "audio-routing" just
> >>>>>>> specifies static routes, so the current description does not allow
> >>>>>>> switching between the two modes either.
> >>>>>>
> >>>>>> Is there no existing mechanism to alter this at runtime?
> >>>>>>
> >>>>>
> >>>>> I don't think so... Since it's currently exposed as two separate DAPM
> >>>>> supplies (instead of a mux or similar) you can only choose between one
> >>>>> of them in the static routes specified by "audio-routing" in the DT.
> >>>>>
> >>>>> I tried looking at how downstream handles this, but this left me even
> >>>>> more confused than I was before. :-) On CRD we currently have the
> >>>>> following routes in DT:
> >>>>>
> >>>>> 	"VA DMIC0", "MIC BIAS3",
> >>>>> 	"VA DMIC1", "MIC BIAS3",
> >>>>> 	"VA DMIC2", "MIC BIAS1",
> >>>>> 	"VA DMIC3", "MIC BIAS1",
> >>>>> 	"VA DMIC0", "VA MIC BIAS3",
> >>>>> 	"VA DMIC1", "VA MIC BIAS3",
> >>>>> 	"VA DMIC2", "VA MIC BIAS1",
> >>>>> 	"VA DMIC3", "VA MIC BIAS1",
> >>>>>
> >>>>> MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
> >>>>> But if you look at e.g. SM8550 downstream they have:
> >>>>>
> >>>>> 	"TX DMIC0", "MIC BIAS3",
> >>>>> 	"TX DMIC1", "MIC BIAS3",
> >>>>> 	"TX DMIC2", "MIC BIAS1",
> >>>>> 	"TX DMIC3", "MIC BIAS1",
> >>>>> 	"VA DMIC0", "VA MIC BIAS3",
> >>>>> 	"VA DMIC1", "VA MIC BIAS3",
> >>>>> 	"VA DMIC2", "VA MIC BIAS1",
> >>>>> 	"VA DMIC3", "VA MIC BIAS1";
> >>>>>
> >>>>> Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
> >>>>> TX macro DMIC, and the low-power one for the VA macro DMIC. That would
> >>>>> be fine.
> >>>>>
> >>>>> Now the question is: If we can use the DMIC through both the TX and the
> >>>>> VA macro, and we're not doing voice activation, why are we using the VA
> >>>>> macro in the first place?
> >>>>>
> >>>>> @Srini: Do you remember why?
> >>>>>
> >>>>
> >>>> What's the verdict regarding this?
> >>>>
> >>>
> >>> We started discussing this, but did not come to a conclusion yet if we
> >>> should be recording from the DMICs using the TX macro instead of the VA
> >>> macro.
> >>>
> >>> The patch I submitted is still valid though, independent of that
> >>> question. Since we're not doing voice activation we want to have the
> >>> "full quality" MIC BIAS supply, not the low-power one.
> >>
> >> Can/should we discuss a new sound API to make this toggleable?
> >>
> >> Do these microphones physically connect to muxable inputs, or does this
> >> depend on board wiring?
> >>
> > 
> > The WCD938x codec has 4 MIC_BIAS output pins that are typically used as
> > power supply for microphones. Inside the codec there is an option to
> > drive these output pins in one of two modes:
> > 
> >  1. Internal regulator to generate the output with a configurable
> >     voltage (qcom,micbiasN-microvolt). Exposed as "MIC BIASn" supply in
> >     the Linux driver.
> > 
> >  2. "Pull-up mode" that bypasses the internal regulator and directly
> >     outputs fixed 1.8V from the VDD_PX pin. Exposed as "VA MIC BIASn"
> >     supply in the Linux driver.
> > 
> > The board-specific part here is only which microphone is wired to which
> > MIC BIAS pin (e.g. DMIC0 -> MIC BIAS3, DMIC2 -> MIC BIAS1 etc). 
> > 
> > Both options will work if the microphone can operate at 1.8V. In that
> > case, I think generally we want (1) for normal audio use cases and (2)
> > for low-power use cases (like "voice activation").
> > 
> > Apparently the same applies for the "macro" to use. TX macro should be
> > used for normal audio, and VA macro only for low-power use cases. With
> > that there is a clear mapping:
> > 
> >  - TX macro DMICs -> full power "MIC BIAS" supply
> >  - VA macro DMICs -> low-power "VA MIC BIAS" supply
> > 
> > I don't see why someone would want to change this mapping, so I don't
> > think it's worth making this user configurable.
> > 
> > Given that we're currently using the VA macro for normal audio, we
> > should describe VA macro DMICs -> full power "MIC BIAS" supply for now
> > and ideally migrate to using the TX macro later.
> 
> So, in short, if I understood you correctly, audio comes in through a
> hardwired connection to a given macro, but the bias pins can be configured
> to output the bias voltage through any of the macros.
> 

That's not entirely right. In our case here, the digital data from the
DMIC goes directly to both the TX and VA macro. The power supply comes
directly from the WCD983x codec. So the macro isn't involved in the bias
voltage at all. Perhaps a picture will help:

                             +------+                         
                        Data |      |  Power                  
                          +--+ DMIC |<----------------+       
                          |  |      |                 |       
                          |  +------+                 |       
    +---------------------+---+    +------------------+------+
    | SoC  +----------+   |   |    | WCD983x       MIC_BIAS1 |
    |      | TX Macro |<--+   |    |                  ^      |
    |      +----------+   |   |    | +-----------+    |      |
    |      +----------+   |   |    | | Regulator +----X--+   |
    |      | VA Macro |<--+   |    | +-----------+       |   |
    |      +----------+       |    |       ^          VDD_PX |
    +-------------------------+    +-------+-----------------+
                                           |             ^    
                                           |             |    

X inside the WCD983x is where we can make the choice, if we want to use
the internal regulator or output VDD_PX on MIC_BIAS1 directly. 

We can also choose to consume the microphone data either via the TX
macro or the VA macro. IIRC there is no mux for this, the data just ends
up in both at the same time.

Does that help explain it?

Thanks,
Stephan

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Konrad Dybcio]

On 9.01.2025 4:45 PM, Stephan Gerhold wrote:
> On Thu, Jan 09, 2025 at 03:00:01PM +0100, Konrad Dybcio wrote:
>> On 9.01.2025 2:29 PM, Stephan Gerhold wrote:
>>> On Thu, Jan 09, 2025 at 01:57:17PM +0100, Konrad Dybcio wrote:
>>>> On 9.01.2025 10:32 AM, Stephan Gerhold wrote:
>>>>> On Wed, Jan 08, 2025 at 05:07:47PM -0600, Bjorn Andersson wrote:
>>>>>> On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
>>>>>>> On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
>>>>>>>> On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
>>>>>>>>> On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
>>>>>>>>>> On 03/12/2024 18:44, Stephan Gerhold wrote:
>>>>>>>>>>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
>>>>>>>>>>>
>>>>>>>>>>>  - "MIC BIASn" enables an internal regulator to generate the output
>>>>>>>>>>>    with a configurable voltage (qcom,micbiasN-microvolt).
>>>>>>>>>>>
>>>>>>>>>>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
>>>>>>>>>>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
>>>>>>>>>>>    This is intended for low-power VA (voice activation) use cases.
>>>>>>>>>>>
>>>>>>>>>>> The audio-routing setup for the X1E80100 CRD currently specifies both
>>>>>>>>>>> as power supplies for the DMICs, but only one of them can be active
>>>>>>>>>>> at the same time. In practice, only the internal regulator is used
>>>>>>>>>>> with the current setup because the driver prefers it over pull-up mode.
>>>>>>>>>>>
>>>>>>>>>>> Make this more clear by dropping the redundant routes to the pull-up
>>>>>>>>>>> "VA MIC BIASn" supply. There is no functional difference except that we
>>>>>>>>>>> skip briefly switching to pull-up mode when shutting down the microphone.
>>>>>>>>>>>
>>>>>>>>>>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
>>>>>>>>>>
>>>>>>>>>> If there is no functional difference and this is just redundant, then
>>>>>>>>>> there is nothing to fix, so drop the tag. But the point is that users
>>>>>>>>>> might want the low-power VA. You claim they don't want... sure, I am
>>>>>>>>>> fine with that but there is nothing to fix in such case.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> The fix here is that two mutually exclusive power supplies for the DMIC
>>>>>>>>> are specified in the device tree. You can only have one of them active
>>>>>>>>> at the same time. The Linux driver handles that gracefully, but the
>>>>>>>>> device tree is still wrong and IMO deserves a fixes tag.
>>>>>>>>>
>>>>>>>>> The functional difference is that we skip briefly switching to pull-up
>>>>>>>>> mode when shutting down the microphone. Users won't notice that, but
>>>>>>>>> it's not the intended behavior.
>>>>>>>>>
>>>>>>>>> I don't claim that users don't want to switch to the low-power pull-up
>>>>>>>>> mode (VA MIC BIASn). However, we would need a different mechanism to
>>>>>>>>> give them the option to switch at runtime. "audio-routing" just
>>>>>>>>> specifies static routes, so the current description does not allow
>>>>>>>>> switching between the two modes either.
>>>>>>>>
>>>>>>>> Is there no existing mechanism to alter this at runtime?
>>>>>>>>
>>>>>>>
>>>>>>> I don't think so... Since it's currently exposed as two separate DAPM
>>>>>>> supplies (instead of a mux or similar) you can only choose between one
>>>>>>> of them in the static routes specified by "audio-routing" in the DT.
>>>>>>>
>>>>>>> I tried looking at how downstream handles this, but this left me even
>>>>>>> more confused than I was before. :-) On CRD we currently have the
>>>>>>> following routes in DT:
>>>>>>>
>>>>>>> 	"VA DMIC0", "MIC BIAS3",
>>>>>>> 	"VA DMIC1", "MIC BIAS3",
>>>>>>> 	"VA DMIC2", "MIC BIAS1",
>>>>>>> 	"VA DMIC3", "MIC BIAS1",
>>>>>>> 	"VA DMIC0", "VA MIC BIAS3",
>>>>>>> 	"VA DMIC1", "VA MIC BIAS3",
>>>>>>> 	"VA DMIC2", "VA MIC BIAS1",
>>>>>>> 	"VA DMIC3", "VA MIC BIAS1",
>>>>>>>
>>>>>>> MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
>>>>>>> But if you look at e.g. SM8550 downstream they have:
>>>>>>>
>>>>>>> 	"TX DMIC0", "MIC BIAS3",
>>>>>>> 	"TX DMIC1", "MIC BIAS3",
>>>>>>> 	"TX DMIC2", "MIC BIAS1",
>>>>>>> 	"TX DMIC3", "MIC BIAS1",
>>>>>>> 	"VA DMIC0", "VA MIC BIAS3",
>>>>>>> 	"VA DMIC1", "VA MIC BIAS3",
>>>>>>> 	"VA DMIC2", "VA MIC BIAS1",
>>>>>>> 	"VA DMIC3", "VA MIC BIAS1";
>>>>>>>
>>>>>>> Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
>>>>>>> TX macro DMIC, and the low-power one for the VA macro DMIC. That would
>>>>>>> be fine.
>>>>>>>
>>>>>>> Now the question is: If we can use the DMIC through both the TX and the
>>>>>>> VA macro, and we're not doing voice activation, why are we using the VA
>>>>>>> macro in the first place?
>>>>>>>
>>>>>>> @Srini: Do you remember why?
>>>>>>>
>>>>>>
>>>>>> What's the verdict regarding this?
>>>>>>
>>>>>
>>>>> We started discussing this, but did not come to a conclusion yet if we
>>>>> should be recording from the DMICs using the TX macro instead of the VA
>>>>> macro.
>>>>>
>>>>> The patch I submitted is still valid though, independent of that
>>>>> question. Since we're not doing voice activation we want to have the
>>>>> "full quality" MIC BIAS supply, not the low-power one.
>>>>
>>>> Can/should we discuss a new sound API to make this toggleable?
>>>>
>>>> Do these microphones physically connect to muxable inputs, or does this
>>>> depend on board wiring?
>>>>
>>>
>>> The WCD938x codec has 4 MIC_BIAS output pins that are typically used as
>>> power supply for microphones. Inside the codec there is an option to
>>> drive these output pins in one of two modes:
>>>
>>>  1. Internal regulator to generate the output with a configurable
>>>     voltage (qcom,micbiasN-microvolt). Exposed as "MIC BIASn" supply in
>>>     the Linux driver.
>>>
>>>  2. "Pull-up mode" that bypasses the internal regulator and directly
>>>     outputs fixed 1.8V from the VDD_PX pin. Exposed as "VA MIC BIASn"
>>>     supply in the Linux driver.
>>>
>>> The board-specific part here is only which microphone is wired to which
>>> MIC BIAS pin (e.g. DMIC0 -> MIC BIAS3, DMIC2 -> MIC BIAS1 etc). 
>>>
>>> Both options will work if the microphone can operate at 1.8V. In that
>>> case, I think generally we want (1) for normal audio use cases and (2)
>>> for low-power use cases (like "voice activation").
>>>
>>> Apparently the same applies for the "macro" to use. TX macro should be
>>> used for normal audio, and VA macro only for low-power use cases. With
>>> that there is a clear mapping:
>>>
>>>  - TX macro DMICs -> full power "MIC BIAS" supply
>>>  - VA macro DMICs -> low-power "VA MIC BIAS" supply
>>>
>>> I don't see why someone would want to change this mapping, so I don't
>>> think it's worth making this user configurable.
>>>
>>> Given that we're currently using the VA macro for normal audio, we
>>> should describe VA macro DMICs -> full power "MIC BIAS" supply for now
>>> and ideally migrate to using the TX macro later.
>>
>> So, in short, if I understood you correctly, audio comes in through a
>> hardwired connection to a given macro, but the bias pins can be configured
>> to output the bias voltage through any of the macros.
>>
> 
> That's not entirely right. In our case here, the digital data from the
> DMIC goes directly to both the TX and VA macro. The power supply comes
> directly from the WCD983x codec. So the macro isn't involved in the bias
> voltage at all. Perhaps a picture will help:
> 
>                              +------+                         
>                         Data |      |  Power                  
>                           +--+ DMIC |<----------------+       
>                           |  |      |                 |       
>                           |  +------+                 |       
>     +---------------------+---+    +------------------+------+
>     | SoC  +----------+   |   |    | WCD983x       MIC_BIAS1 |
>     |      | TX Macro |<--+   |    |                  ^      |
>     |      +----------+   |   |    | +-----------+    |      |
>     |      +----------+   |   |    | | Regulator +----X--+   |
>     |      | VA Macro |<--+   |    | +-----------+       |   |
>     |      +----------+       |    |       ^          VDD_PX |
>     +-------------------------+    +-------+-----------------+
>                                            |             ^    
>                                            |             |    
> 
> X inside the WCD983x is where we can make the choice, if we want to use
> the internal regulator or output VDD_PX on MIC_BIAS1 directly. 
> 
> We can also choose to consume the microphone data either via the TX
> macro or the VA macro. IIRC there is no mux for this, the data just ends
> up in both at the same time.
> 
> Does that help explain it?

I think that's a "sadly, yes" ;)

Because that means we can switch the mics to e.g. the VA macro for
low power always-listening usecases at runtime (e.g. screen off), but we
may want to push it back to the RX macro for $reasons. And I'm assuming
there's probably $reasons2 to use the matching bias output from WCD..

Unless both $reasons are bogus, in which case we should probably stick
to keeping the bias and consuming macro paired to make the DT look sane

Konrad

Re: [PATCH 2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies

[Stephan Gerhold]

On Thu, Jan 09, 2025 at 05:32:18PM +0100, Konrad Dybcio wrote:
> On 9.01.2025 4:45 PM, Stephan Gerhold wrote:
> > On Thu, Jan 09, 2025 at 03:00:01PM +0100, Konrad Dybcio wrote:
> >> On 9.01.2025 2:29 PM, Stephan Gerhold wrote:
> >>> On Thu, Jan 09, 2025 at 01:57:17PM +0100, Konrad Dybcio wrote:
> >>>> On 9.01.2025 10:32 AM, Stephan Gerhold wrote:
> >>>>> On Wed, Jan 08, 2025 at 05:07:47PM -0600, Bjorn Andersson wrote:
> >>>>>> On Thu, Dec 05, 2024 at 07:46:28PM +0100, Stephan Gerhold wrote:
> >>>>>>> On Thu, Dec 05, 2024 at 06:11:47PM +0100, Konrad Dybcio wrote:
> >>>>>>>> On 4.12.2024 9:33 AM, Stephan Gerhold wrote:
> >>>>>>>>> On Wed, Dec 04, 2024 at 08:20:15AM +0100, Krzysztof Kozlowski wrote:
> >>>>>>>>>> On 03/12/2024 18:44, Stephan Gerhold wrote:
> >>>>>>>>>>> The WCD938x codec provides two controls for each of the MIC_BIASn outputs:
> >>>>>>>>>>>
> >>>>>>>>>>>  - "MIC BIASn" enables an internal regulator to generate the output
> >>>>>>>>>>>    with a configurable voltage (qcom,micbiasN-microvolt).
> >>>>>>>>>>>
> >>>>>>>>>>>  - "VA MIC BIASn" enables "pull-up mode" that bypasses the internal
> >>>>>>>>>>>    regulator and directly outputs fixed 1.8V from the VDD_PX pin.
> >>>>>>>>>>>    This is intended for low-power VA (voice activation) use cases.
> >>>>>>>>>>>
> >>>>>>>>>>> The audio-routing setup for the X1E80100 CRD currently specifies both
> >>>>>>>>>>> as power supplies for the DMICs, but only one of them can be active
> >>>>>>>>>>> at the same time. In practice, only the internal regulator is used
> >>>>>>>>>>> with the current setup because the driver prefers it over pull-up mode.
> >>>>>>>>>>>
> >>>>>>>>>>> Make this more clear by dropping the redundant routes to the pull-up
> >>>>>>>>>>> "VA MIC BIASn" supply. There is no functional difference except that we
> >>>>>>>>>>> skip briefly switching to pull-up mode when shutting down the microphone.
> >>>>>>>>>>>
> >>>>>>>>>>> Fixes: 4442a67eedc1 ("arm64: dts: qcom: x1e80100-crd: add sound card")
> >>>>>>>>>>
> >>>>>>>>>> If there is no functional difference and this is just redundant, then
> >>>>>>>>>> there is nothing to fix, so drop the tag. But the point is that users
> >>>>>>>>>> might want the low-power VA. You claim they don't want... sure, I am
> >>>>>>>>>> fine with that but there is nothing to fix in such case.
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> The fix here is that two mutually exclusive power supplies for the DMIC
> >>>>>>>>> are specified in the device tree. You can only have one of them active
> >>>>>>>>> at the same time. The Linux driver handles that gracefully, but the
> >>>>>>>>> device tree is still wrong and IMO deserves a fixes tag.
> >>>>>>>>>
> >>>>>>>>> The functional difference is that we skip briefly switching to pull-up
> >>>>>>>>> mode when shutting down the microphone. Users won't notice that, but
> >>>>>>>>> it's not the intended behavior.
> >>>>>>>>>
> >>>>>>>>> I don't claim that users don't want to switch to the low-power pull-up
> >>>>>>>>> mode (VA MIC BIASn). However, we would need a different mechanism to
> >>>>>>>>> give them the option to switch at runtime. "audio-routing" just
> >>>>>>>>> specifies static routes, so the current description does not allow
> >>>>>>>>> switching between the two modes either.
> >>>>>>>>
> >>>>>>>> Is there no existing mechanism to alter this at runtime?
> >>>>>>>>
> >>>>>>>
> >>>>>>> I don't think so... Since it's currently exposed as two separate DAPM
> >>>>>>> supplies (instead of a mux or similar) you can only choose between one
> >>>>>>> of them in the static routes specified by "audio-routing" in the DT.
> >>>>>>>
> >>>>>>> I tried looking at how downstream handles this, but this left me even
> >>>>>>> more confused than I was before. :-) On CRD we currently have the
> >>>>>>> following routes in DT:
> >>>>>>>
> >>>>>>> 	"VA DMIC0", "MIC BIAS3",
> >>>>>>> 	"VA DMIC1", "MIC BIAS3",
> >>>>>>> 	"VA DMIC2", "MIC BIAS1",
> >>>>>>> 	"VA DMIC3", "MIC BIAS1",
> >>>>>>> 	"VA DMIC0", "VA MIC BIAS3",
> >>>>>>> 	"VA DMIC1", "VA MIC BIAS3",
> >>>>>>> 	"VA DMIC2", "VA MIC BIAS1",
> >>>>>>> 	"VA DMIC3", "VA MIC BIAS1",
> >>>>>>>
> >>>>>>> MIC BIAS and VA MIC BIAS are mutually exclusive, so this is not correct.
> >>>>>>> But if you look at e.g. SM8550 downstream they have:
> >>>>>>>
> >>>>>>> 	"TX DMIC0", "MIC BIAS3",
> >>>>>>> 	"TX DMIC1", "MIC BIAS3",
> >>>>>>> 	"TX DMIC2", "MIC BIAS1",
> >>>>>>> 	"TX DMIC3", "MIC BIAS1",
> >>>>>>> 	"VA DMIC0", "VA MIC BIAS3",
> >>>>>>> 	"VA DMIC1", "VA MIC BIAS3",
> >>>>>>> 	"VA DMIC2", "VA MIC BIAS1",
> >>>>>>> 	"VA DMIC3", "VA MIC BIAS1";
> >>>>>>>
> >>>>>>> Note the TX DMIC vs VA DMIC. So they specify one of the supplies for the
> >>>>>>> TX macro DMIC, and the low-power one for the VA macro DMIC. That would
> >>>>>>> be fine.
> >>>>>>>
> >>>>>>> Now the question is: If we can use the DMIC through both the TX and the
> >>>>>>> VA macro, and we're not doing voice activation, why are we using the VA
> >>>>>>> macro in the first place?
> >>>>>>>
> >>>>>>> @Srini: Do you remember why?
> >>>>>>>
> >>>>>>
> >>>>>> What's the verdict regarding this?
> >>>>>>
> >>>>>
> >>>>> We started discussing this, but did not come to a conclusion yet if we
> >>>>> should be recording from the DMICs using the TX macro instead of the VA
> >>>>> macro.
> >>>>>
> >>>>> The patch I submitted is still valid though, independent of that
> >>>>> question. Since we're not doing voice activation we want to have the
> >>>>> "full quality" MIC BIAS supply, not the low-power one.
> >>>>
> >>>> Can/should we discuss a new sound API to make this toggleable?
> >>>>
> >>>> Do these microphones physically connect to muxable inputs, or does this
> >>>> depend on board wiring?
> >>>>
> >>>
> >>> The WCD938x codec has 4 MIC_BIAS output pins that are typically used as
> >>> power supply for microphones. Inside the codec there is an option to
> >>> drive these output pins in one of two modes:
> >>>
> >>>  1. Internal regulator to generate the output with a configurable
> >>>     voltage (qcom,micbiasN-microvolt). Exposed as "MIC BIASn" supply in
> >>>     the Linux driver.
> >>>
> >>>  2. "Pull-up mode" that bypasses the internal regulator and directly
> >>>     outputs fixed 1.8V from the VDD_PX pin. Exposed as "VA MIC BIASn"
> >>>     supply in the Linux driver.
> >>>
> >>> The board-specific part here is only which microphone is wired to which
> >>> MIC BIAS pin (e.g. DMIC0 -> MIC BIAS3, DMIC2 -> MIC BIAS1 etc). 
> >>>
> >>> Both options will work if the microphone can operate at 1.8V. In that
> >>> case, I think generally we want (1) for normal audio use cases and (2)
> >>> for low-power use cases (like "voice activation").
> >>>
> >>> Apparently the same applies for the "macro" to use. TX macro should be
> >>> used for normal audio, and VA macro only for low-power use cases. With
> >>> that there is a clear mapping:
> >>>
> >>>  - TX macro DMICs -> full power "MIC BIAS" supply
> >>>  - VA macro DMICs -> low-power "VA MIC BIAS" supply
> >>>
> >>> I don't see why someone would want to change this mapping, so I don't
> >>> think it's worth making this user configurable.
> >>>
> >>> Given that we're currently using the VA macro for normal audio, we
> >>> should describe VA macro DMICs -> full power "MIC BIAS" supply for now
> >>> and ideally migrate to using the TX macro later.
> >>
> >> So, in short, if I understood you correctly, audio comes in through a
> >> hardwired connection to a given macro, but the bias pins can be configured
> >> to output the bias voltage through any of the macros.
> >>
> > 
> > That's not entirely right. In our case here, the digital data from the
> > DMIC goes directly to both the TX and VA macro. The power supply comes
> > directly from the WCD983x codec. So the macro isn't involved in the bias
> > voltage at all. Perhaps a picture will help:
> > 
> >                              +------+                         
> >                         Data |      |  Power                  
> >                           +--+ DMIC |<----------------+       
> >                           |  |      |                 |       
> >                           |  +------+                 |       
> >     +---------------------+---+    +------------------+------+
> >     | SoC  +----------+   |   |    | WCD983x       MIC_BIAS1 |
> >     |      | TX Macro |<--+   |    |                  ^      |
> >     |      +----------+   |   |    | +-----------+    |      |
> >     |      +----------+   |   |    | | Regulator +----X--+   |
> >     |      | VA Macro |<--+   |    | +-----------+       |   |
> >     |      +----------+       |    |       ^          VDD_PX |
> >     +-------------------------+    +-------+-----------------+
> >                                            |             ^    
> >                                            |             |    
> > 
> > X inside the WCD983x is where we can make the choice, if we want to use
> > the internal regulator or output VDD_PX on MIC_BIAS1 directly. 
> > 
> > We can also choose to consume the microphone data either via the TX
> > macro or the VA macro. IIRC there is no mux for this, the data just ends
> > up in both at the same time.
> > 
> > Does that help explain it?
> 
> I think that's a "sadly, yes" ;)
> 
> Because that means we can switch the mics to e.g. the VA macro for
> low power always-listening usecases at runtime (e.g. screen off), but we
> may want to push it back to the RX macro for $reasons. And I'm assuming
> there's probably $reasons2 to use the matching bias output from WCD..
> 
> Unless both $reasons are bogus, in which case we should probably stick
> to keeping the bias and consuming macro paired to make the DT look sane

I think both $reasons boil down to saving power. If you do
always-listening use cases you likely care more about power than perfect
quality or functionality. So you either pick

 - Quality + functionality => Internal MIC bias regulator + TX macro, or
 - Low-power => Pull-up MIC BIAS + VA macro

_Maybe_ someone wants one of the other combinations, but I don't think
those are useful enough to warrant refactoring of the driver and
potentially breaking DTB compatibility.

Thanks,
Stephan

Re: [PATCH 0/2] arm64: dts: qcom: Drop duplicate DMIC supplies for X13S/CRD

[Bjorn Andersson]

On Tue, 03 Dec 2024 18:44:01 +0100, Stephan Gerhold wrote:
> Drop the duplicated MIC BIAS supplies in "audio-routing" for the ThinkPad
> X13S and the X1E80100. "MIC BIASn" and "VA MIC BIASn" are mutually
> exclusive, only one of them can be active at the same time.
> 
> 

Applied, thanks!

[1/2] arm64: dts: qcom: sc8280xp-x13s: Drop duplicate DMIC supplies
      commit: a2e617f4e6981aa514a569e927f90b0d39bb31b2
[2/2] arm64: dts: qcom: x1e80100-crd: Drop duplicate DMIC supplies
      commit: b49e37de8e70bc433b526a9f4382f72b7ac6492e

Best regards,
-- 
Bjorn Andersson <andersson@kernel.org>