[PATCH 1/3] ASoC: wm8940: Remove warning when no plat data

[PATCH 1/3] ASoC: wm8940: Remove warning when no plat data

[Lukasz Majewski]

The lack of platform data in the contemporary Linux
shall not be the reason to display warnings to the
kernel logs.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
---
 sound/soc/codecs/wm8940.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/sound/soc/codecs/wm8940.c b/sound/soc/codecs/wm8940.c
index 440d048ef0c0..7cea54720436 100644
--- a/sound/soc/codecs/wm8940.c
+++ b/sound/soc/codecs/wm8940.c
@@ -709,9 +709,7 @@ static int wm8940_probe(struct snd_soc_component *component)
 	if (ret < 0)
 		return ret;
 
-	if (!pdata)
-		dev_warn(component->dev, "No platform data supplied\n");
-	else {
+	if (pdata) {
 		reg = snd_soc_component_read(component, WM8940_OUTPUTCTL);
 		ret = snd_soc_component_write(component, WM8940_OUTPUTCTL, reg | pdata->vroi);
 		if (ret < 0)
-- 
2.20.1

[PATCH 2/3] ASoC: wm8940: Rewrite code to set proper clocks

[Lukasz Majewski]

Without this change, the wm8940 driver is not working when
set_sysclk callback (wm8940_set_dai_sysclk) is called with
freqency not listed in the switch clause.

This change adjusts this driver to allow non-standard frequency
set (just after the boot) being adjusted afterwards by the sound
system core code.

Moreover, support for internal wm8940's PLL is provided, so it
can generate clocks when HOST system is not able to do it.

Code in this commit is based on previous change done for wm8974
(SHA1: 51b2bb3f2568e6d9d81a001d38b8d70c2ba4af99).

Signed-off-by: Lukasz Majewski <lukma@denx.de>
---
 sound/soc/codecs/wm8940.c | 103 ++++++++++++++++++++++++++++++--------
 1 file changed, 83 insertions(+), 20 deletions(-)

diff --git a/sound/soc/codecs/wm8940.c b/sound/soc/codecs/wm8940.c
index 7cea54720436..6fb1c3780439 100644
--- a/sound/soc/codecs/wm8940.c
+++ b/sound/soc/codecs/wm8940.c
@@ -37,7 +37,9 @@
 #include "wm8940.h"
 
 struct wm8940_priv {
-	unsigned int sysclk;
+	unsigned int mclk;
+	unsigned int fs;
+
 	struct regmap *regmap;
 };
 
@@ -387,17 +389,24 @@ static int wm8940_set_dai_fmt(struct snd_soc_dai *codec_dai,
 	return 0;
 }
 
+static int wm8940_update_clocks(struct snd_soc_dai *dai);
 static int wm8940_i2s_hw_params(struct snd_pcm_substream *substream,
 				struct snd_pcm_hw_params *params,
 				struct snd_soc_dai *dai)
 {
 	struct snd_soc_component *component = dai->component;
+	struct wm8940_priv *wm8940 = snd_soc_component_get_drvdata(component);
 	u16 iface = snd_soc_component_read(component, WM8940_IFACE) & 0xFD9F;
 	u16 addcntrl = snd_soc_component_read(component, WM8940_ADDCNTRL) & 0xFFF1;
 	u16 companding =  snd_soc_component_read(component,
 						WM8940_COMPANDINGCTL) & 0xFFDF;
 	int ret;
 
+	wm8940->fs = params_rate(params);
+	ret = wm8940_update_clocks(dai);
+	if (ret)
+		return ret;
+
 	/* LoutR control */
 	if (substream->stream == SNDRV_PCM_STREAM_CAPTURE
 	    && params_channels(params) == 2)
@@ -496,7 +505,6 @@ static int wm8940_set_bias_level(struct snd_soc_component *component,
 				return ret;
 			}
 		}
-
 		/* ensure bufioen and biasen */
 		pwr_reg |= (1 << 2) | (1 << 3);
 		/* set vmid to 300k for standby */
@@ -611,24 +619,6 @@ static int wm8940_set_dai_pll(struct snd_soc_dai *codec_dai, int pll_id,
 	return 0;
 }
 
-static int wm8940_set_dai_sysclk(struct snd_soc_dai *codec_dai,
-				 int clk_id, unsigned int freq, int dir)
-{
-	struct snd_soc_component *component = codec_dai->component;
-	struct wm8940_priv *wm8940 = snd_soc_component_get_drvdata(component);
-
-	switch (freq) {
-	case 11289600:
-	case 12000000:
-	case 12288000:
-	case 16934400:
-	case 18432000:
-		wm8940->sysclk = freq;
-		return 0;
-	}
-	return -EINVAL;
-}
-
 static int wm8940_set_dai_clkdiv(struct snd_soc_dai *codec_dai,
 				 int div_id, int div)
 {
@@ -653,6 +643,79 @@ static int wm8940_set_dai_clkdiv(struct snd_soc_dai *codec_dai,
 	return ret;
 }
 
+static unsigned int wm8940_get_mclkdiv(unsigned int f_in, unsigned int f_out,
+				       int *mclkdiv)
+{
+	unsigned int ratio = 2 * f_in / f_out;
+
+	if (ratio <= 2) {
+		*mclkdiv = WM8940_MCLKDIV_1;
+		ratio = 2;
+	} else if (ratio == 3) {
+		*mclkdiv = WM8940_MCLKDIV_1_5;
+	} else if (ratio == 4) {
+		*mclkdiv = WM8940_MCLKDIV_2;
+	} else if (ratio <= 6) {
+		*mclkdiv = WM8940_MCLKDIV_3;
+		ratio = 6;
+	} else if (ratio <= 8) {
+		*mclkdiv = WM8940_MCLKDIV_4;
+		ratio = 8;
+	} else if (ratio <= 12) {
+		*mclkdiv = WM8940_MCLKDIV_6;
+		ratio = 12;
+	} else if (ratio <= 16) {
+		*mclkdiv = WM8940_MCLKDIV_8;
+		ratio = 16;
+	} else {
+		*mclkdiv = WM8940_MCLKDIV_12;
+		ratio = 24;
+	}
+
+	return f_out * ratio / 2;
+}
+
+static int wm8940_update_clocks(struct snd_soc_dai *dai)
+{
+	struct snd_soc_component *component = dai->component;
+	struct wm8940_priv *priv = snd_soc_component_get_drvdata(component);
+	unsigned int fs256;
+	unsigned int fpll = 0;
+	unsigned int f;
+	int mclkdiv;
+
+	if (!priv->mclk || !priv->fs)
+		return 0;
+
+	fs256 = 256 * priv->fs;
+
+	f = wm8940_get_mclkdiv(priv->mclk, fs256, &mclkdiv);
+	if (f != priv->mclk) {
+		/* The PLL performs best around 90MHz */
+		fpll = wm8940_get_mclkdiv(22500000, fs256, &mclkdiv);
+	}
+
+	wm8940_set_dai_pll(dai, 0, 0, priv->mclk, fpll);
+	wm8940_set_dai_clkdiv(dai, WM8940_MCLKDIV, mclkdiv);
+
+	return 0;
+}
+
+static int wm8940_set_dai_sysclk(struct snd_soc_dai *dai, int clk_id,
+				 unsigned int freq, int dir)
+{
+	struct snd_soc_component *component = dai->component;
+	struct wm8940_priv *priv = snd_soc_component_get_drvdata(component);
+
+	if (dir != SND_SOC_CLOCK_IN)
+		return -EINVAL;
+
+	priv->mclk = freq;
+
+	return wm8940_update_clocks(dai);
+}
+
+
 #define WM8940_RATES SNDRV_PCM_RATE_8000_48000
 
 #define WM8940_FORMATS (SNDRV_PCM_FMTBIT_S8 |				\
-- 
2.20.1

[PATCH 3/3] ASoC: wm8940: Mute also the speaker output

[Lukasz Majewski]

Without this change the BTL speaker produces some
"distortion" noise when test program
(speaker-test -t waw) is ended with ctrl+c.

As our design uses speaker outputs to drive BTL speaker,
it was necessary to also mute the speaker via the codec
internal WM8940_SPKVOL register with setting
WM8940_SPKMUTE bit.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
---
 sound/soc/codecs/wm8940.c | 11 ++++++++++-
 sound/soc/codecs/wm8940.h |  3 +++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/wm8940.c b/sound/soc/codecs/wm8940.c
index 6fb1c3780439..a8596f4089dd 100644
--- a/sound/soc/codecs/wm8940.c
+++ b/sound/soc/codecs/wm8940.c
@@ -465,9 +465,18 @@ static int wm8940_mute(struct snd_soc_dai *dai, int mute, int direction)
 {
 	struct snd_soc_component *component = dai->component;
 	u16 mute_reg = snd_soc_component_read(component, WM8940_DAC) & 0xffbf;
+	u16 spkvol_reg = snd_soc_component_read(component, WM8940_SPKVOL);
+	int ret;
 
-	if (mute)
+	spkvol_reg &= ~WM8940_SPKMUTE;
+	if (mute) {
 		mute_reg |= 0x40;
+		spkvol_reg |= WM8940_SPKMUTE;
+	}
+
+	ret = snd_soc_component_write(component, WM8940_SPKVOL, spkvol_reg);
+	if (ret)
+		return ret;
 
 	return snd_soc_component_write(component, WM8940_DAC, mute_reg);
 }
diff --git a/sound/soc/codecs/wm8940.h b/sound/soc/codecs/wm8940.h
index 0d4f53ada2e6..eb051ed29bb8 100644
--- a/sound/soc/codecs/wm8940.h
+++ b/sound/soc/codecs/wm8940.h
@@ -95,5 +95,8 @@ struct wm8940_setup_data {
 #define WM8940_OPCLKDIV_3 2
 #define WM8940_OPCLKDIV_4 3
 
+/* Bit definitions */
+#define WM8940_SPKMUTE BIT(6)
+
 #endif /* _WM8940_H */
 
-- 
2.20.1

Re: [PATCH 1/3] ASoC: wm8940: Remove warning when no plat data

[Mark Brown]

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On Mon, Jun 06, 2022 at 05:44:39PM +0200, Lukasz Majewski wrote:
> The lack of platform data in the contemporary Linux
> shall not be the reason to display warnings to the
> kernel logs.
> 
> Signed-off-by: Lukasz Majewski <lukma@denx.de>

Given that the device requires configuration and doesn't appear to have
any other firmware interface support that's rather a strong statement...

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Re: [PATCH 1/3] ASoC: wm8940: Remove warning when no plat data

[Lukasz Majewski]

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Hi Mark,

> On Mon, Jun 06, 2022 at 05:44:39PM +0200, Lukasz Majewski wrote:
> > The lack of platform data in the contemporary Linux
> > shall not be the reason to display warnings to the
> > kernel logs.
> > 
> > Signed-off-by: Lukasz Majewski <lukma@denx.de>  
> 
> Given that the device requires configuration and doesn't appear to
> have any other firmware interface support that's rather a strong
> statement...

Thanks for the comment :-)

My point is that - similar codec - wm8974 don't display such warnings.
(this code was not updated/refactored for a quite long time).

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

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Re: [PATCH 2/3] ASoC: wm8940: Rewrite code to set proper clocks

[Mark Brown]

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On Mon, Jun 06, 2022 at 05:44:40PM +0200, Lukasz Majewski wrote:
> Without this change, the wm8940 driver is not working when
> set_sysclk callback (wm8940_set_dai_sysclk) is called with
> freqency not listed in the switch clause.

> This change adjusts this driver to allow non-standard frequency
> set (just after the boot) being adjusted afterwards by the sound
> system core code.

I don't entirely follow the above - in what way might the core adjust
the clocking, and why would we want to allow the use of invalid clocks?
Surely that just makes error checking worse.

> Code in this commit is based on previous change done for wm8974
> (SHA1: 51b2bb3f2568e6d9d81a001d38b8d70c2ba4af99).

Please include human readable descriptions of things like commits and
issues being discussed in e-mail in your mails, this makes them much
easier for humans to read especially when they have no internet access.
I do frequently catch up on my mail on flights or while otherwise
travelling so this is even more pressing for me than just being about
making things a bit easier to read.

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Re: [PATCH 3/3] ASoC: wm8940: Mute also the speaker output

[Mark Brown]

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On Mon, Jun 06, 2022 at 05:44:41PM +0200, Lukasz Majewski wrote:

> Without this change the BTL speaker produces some
> "distortion" noise when test program
> (speaker-test -t waw) is ended with ctrl+c.

> As our design uses speaker outputs to drive BTL speaker,
> it was necessary to also mute the speaker via the codec
> internal WM8940_SPKVOL register with setting
> WM8940_SPKMUTE bit.

This will not interact well with both the user visible control of the
speaker volume via the Speaker Playback Volume control and the analog
bypass paths that the device has - it'll change the state of the control
without generating any events, and cut off any bypassed audio that's
mixed in.

You can probably achieve a similar effect by making the control an
_AUTODISABLE one which will allow the core to mute the control when it's
not being used in a way that's not visible to userspace.

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Re: [PATCH 1/3] ASoC: wm8940: Remove warning when no plat data

[Mark Brown]

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On Mon, Jun 06, 2022 at 06:17:31PM +0200, Lukasz Majewski wrote:
> > On Mon, Jun 06, 2022 at 05:44:39PM +0200, Lukasz Majewski wrote:

> > > The lack of platform data in the contemporary Linux
> > > shall not be the reason to display warnings to the
> > > kernel logs.

> > Given that the device requires configuration and doesn't appear to
> > have any other firmware interface support that's rather a strong
> > statement...

> My point is that - similar codec - wm8974 don't display such warnings.
> (this code was not updated/refactored for a quite long time).

Perhaps those drivers are buggy, or those devices lack this specific
configuration that's being adjusted?  The changelog should at least
address why the driver was warning about configuration being required
but it's safe to ignore that.

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Re: [PATCH 2/3] ASoC: wm8940: Rewrite code to set proper clocks

[Lukasz Majewski]

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Hi Mark,

> On Mon, Jun 06, 2022 at 05:44:40PM +0200, Lukasz Majewski wrote:
> > Without this change, the wm8940 driver is not working when
> > set_sysclk callback (wm8940_set_dai_sysclk) is called with
> > freqency not listed in the switch clause.  
> 
> > This change adjusts this driver to allow non-standard frequency
> > set (just after the boot) being adjusted afterwards by the sound
> > system core code.  
> 
> I don't entirely follow the above - in what way might the core adjust
> the clocking, and why would we want to allow the use of invalid
> clocks? Surely that just makes error checking worse.

Hmm, it is a bit complicated.

When I enabed wm8940 support in mainline - the first call to
wm8940_set_dai_sysclk (the set_sysclk callback) required mclk = 11997070
frequency.

With the current code [1] the initialization of the codec returns
-EINVAL and the codec is not supported in the system:

asoc-simple-card: probe of sound failed with error -22



The approach used in this patch set to fix the above issue is based on
one already present in-tree for wm8974 codec.

> 
> > Code in this commit is based on previous change done for wm8974
> > (SHA1: 51b2bb3f2568e6d9d81a001d38b8d70c2ba4af99).  
> 
> Please include human readable descriptions of things like commits and
> issues being discussed in e-mail in your mails, this makes them much
> easier for humans to read especially when they have no internet
> access. 

Ok, I will add some more verbose description. The aforementioned SHA1
is referring to commit already in-tree, so you would find it easily
even without the Internet.

> I do frequently catch up on my mail on flights or while
> otherwise travelling so this is even more pressing for me than just
> being about making things a bit easier to read.

+1

Links:

[1] -
https://elixir.bootlin.com/linux/v5.18.1/source/sound/soc/codecs/wm8940.c#L614

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

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Re: [PATCH 2/3] ASoC: wm8940: Rewrite code to set proper clocks

[Mark Brown]

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On Tue, Jun 07, 2022 at 02:13:09PM +0200, Lukasz Majewski wrote:
> > On Mon, Jun 06, 2022 at 05:44:40PM +0200, Lukasz Majewski wrote:

> > I don't entirely follow the above - in what way might the core adjust
> > the clocking, and why would we want to allow the use of invalid
> > clocks? Surely that just makes error checking worse.

> Hmm, it is a bit complicated.

> When I enabed wm8940 support in mainline - the first call to
> wm8940_set_dai_sysclk (the set_sysclk callback) required mclk = 11997070
> frequency.

> With the current code [1] the initialization of the codec returns
> -EINVAL and the codec is not supported in the system:

> asoc-simple-card: probe of sound failed with error -22

Well, that looks like a bug in either simple-card or it's configuration
which should be fixed then (you should probably use audio-graph-card for
new things BTW).  If a machine driver just randomly sets a clock rate
that the system can't support and doesn't want then that's a problem,
presuambly it's getting that rate from somewhere.  Note that this is the
machine driver trying to set a clock rate, not the core.

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Re: [PATCH 1/3] ASoC: wm8940: Remove warning when no plat data

[Lukasz Majewski]

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Hi Mark,

> On Mon, Jun 06, 2022 at 06:17:31PM +0200, Lukasz Majewski wrote:
> > > On Mon, Jun 06, 2022 at 05:44:39PM +0200, Lukasz Majewski wrote:  
> 
> > > > The lack of platform data in the contemporary Linux
> > > > shall not be the reason to display warnings to the
> > > > kernel logs.  
> 
> > > Given that the device requires configuration and doesn't appear to
> > > have any other firmware interface support that's rather a strong
> > > statement...  
> 
> > My point is that - similar codec - wm8974 don't display such
> > warnings. (this code was not updated/refactored for a quite long
> > time).  
> 
> Perhaps those drivers are buggy, or those devices lack this specific
> configuration that's being adjusted?  The changelog should at least
> address why the driver was warning about configuration being required
> but it's safe to ignore that.

With v4.4 from which I forward port those changes only the PXA
'stargate2' mach is using this codec.

In this version there is no reference to 'vroi'.

With newest Linux - there is no reference to this codec (even to any
DTS file), so we can assume that from at least v4.4 there is no
reference to platform data for it.


I guess that one can provide the 'vroi' information via DTS nowadays if
required.


Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

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Re: [PATCH 1/3] ASoC: wm8940: Remove warning when no plat data

[Mark Brown]

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On Tue, Jun 07, 2022 at 02:30:39PM +0200, Lukasz Majewski wrote:
> > On Mon, Jun 06, 2022 at 06:17:31PM +0200, Lukasz Majewski wrote:
> > > > On Mon, Jun 06, 2022 at 05:44:39PM +0200, Lukasz Majewski wrote:  

> > > My point is that - similar codec - wm8974 don't display such
> > > warnings. (this code was not updated/refactored for a quite long
> > > time).  

> > Perhaps those drivers are buggy, or those devices lack this specific
> > configuration that's being adjusted?  The changelog should at least
> > address why the driver was warning about configuration being required
> > but it's safe to ignore that.

> With v4.4 from which I forward port those changes only the PXA
> 'stargate2' mach is using this codec.

> In this version there is no reference to 'vroi'.

That's equivalent to setting a value of 0 given the way platform data
works.

> I guess that one can provide the 'vroi' information via DTS nowadays if
> required.

Yes, that's what I'd expect.

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Re: [PATCH 3/3] ASoC: wm8940: Mute also the speaker output

[Lukasz Majewski]

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Hi Mark,

> On Mon, Jun 06, 2022 at 05:44:41PM +0200, Lukasz Majewski wrote:
> 
> > Without this change the BTL speaker produces some
> > "distortion" noise when test program
> > (speaker-test -t waw) is ended with ctrl+c.  
> 
> > As our design uses speaker outputs to drive BTL speaker,
> > it was necessary to also mute the speaker via the codec
> > internal WM8940_SPKVOL register with setting
> > WM8940_SPKMUTE bit.  
> 
> This will not interact well with both the user visible control of the
> speaker volume via the Speaker Playback Volume control and the analog
> bypass paths that the device has - it'll change the state of the
> control without generating any events, and cut off any bypassed audio
> that's mixed in.
> 

I'm wondering why it is safe to call DAI's .digital_mute()
callback, which explicitly changes state of the "DAC soft mute enable"
bit (DACMU) ?

And on the other hand it is not correct to just mute the speakers?

> You can probably achieve a similar effect by making the control an
> _AUTODISABLE one which will allow the core to mute the control when
> it's not being used in a way that's not visible to userspace.

The exact definition for the event, which I'm forcing above:

SOC_SINGLE("Speaker Playback Switch", WM8940_SPKVOL,  6, 1, 1),

And there is no SOC_SINGLE_AUTODISABLE() macro available.


The issue I'm trying to fix:

- The mclk clock is stopped (after some time) by imx SOC when I end
  'speaker-test' program with ctrl+c.

- When the clock is not provided (after ~1sec) I do hear a single short
  noise from speakers.

- The other solution (which also works) would be to enable clock once
  (during probe) and then do not disable it till system is powered
  off (yes it is a hack :-) ).


I'm wondering if this can be fixed by some 'amixer' user space switch?

Thanks in advance for help.

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de

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Re: [PATCH 3/3] ASoC: wm8940: Mute also the speaker output

[Mark Brown]

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On Fri, Jun 10, 2022 at 11:23:31AM +0200, Lukasz Majewski wrote:
> > On Mon, Jun 06, 2022 at 05:44:41PM +0200, Lukasz Majewski wrote:

> > > Without this change the BTL speaker produces some
> > > "distortion" noise when test program
> > > (speaker-test -t waw) is ended with ctrl+c.  

> > > As our design uses speaker outputs to drive BTL speaker,
> > > it was necessary to also mute the speaker via the codec
> > > internal WM8940_SPKVOL register with setting
> > > WM8940_SPKMUTE bit.  

> > This will not interact well with both the user visible control of the
> > speaker volume via the Speaker Playback Volume control and the analog
> > bypass paths that the device has - it'll change the state of the
> > control without generating any events, and cut off any bypassed audio
> > that's mixed in.

> I'm wondering why it is safe to call DAI's .digital_mute()
> callback, which explicitly changes state of the "DAC soft mute enable"
> bit (DACMU) ?

If there's a user visible control for the same register bit that's a
bug.  If there's no user visible control for it then there's nothing to
conflict with.

> And on the other hand it is not correct to just mute the speakers?

No, that's not what we're muting playback for - the digital mute is
there specifically to deal with issues with host controllers outputing
noise during startup/teardown.  If there are issues with the speaker
output then they need to be addressed at that point, especially given
that the device has bypass paths.

> > You can probably achieve a similar effect by making the control an
> > _AUTODISABLE one which will allow the core to mute the control when
> > it's not being used in a way that's not visible to userspace.

> The exact definition for the event, which I'm forcing above:

> SOC_SINGLE("Speaker Playback Switch", WM8940_SPKVOL,  6, 1, 1),

> And there is no SOC_SINGLE_AUTODISABLE() macro available.

That seems solvable?  Though if the issue isn't triggered in connection
with a DAPM event (which sounds like the case) then it's probably not
going to help.

> The issue I'm trying to fix:

> - The mclk clock is stopped (after some time) by imx SOC when I end
>   'speaker-test' program with ctrl+c.

> - When the clock is not provided (after ~1sec) I do hear a single short
>   noise from speakers.

> - The other solution (which also works) would be to enable clock once
>   (during probe) and then do not disable it till system is powered
>   off (yes it is a hack :-) ).

If the issue is triggered by the MCLK being disabled prematurely then
the simplest fix is probably to wire up the CODEC MCLK to the clock API
and manage it during set_bias_level() (probably on transition out of and
into _STANDBY) - that should have a similar effect to leaving it enabled
all the time.

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