[alsa-devel] [PATCH v2 0/3] ASoC: max98090: fix PLL unlocked workaround-related

[alsa-devel] [PATCH v2 0/3] ASoC: max98090: fix PLL unlocked workaround-related

[Tzung-Bi Shih]

This series is a follow up fix for the question:
https://mailman.alsa-project.org/pipermail/alsa-devel/2019-October/157364.html

Changes from v1:
ASoC: max98090: remove msleep in PLL unlocked workaround
- add more comments
https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/158969.html

ASoC: max98090: exit workaround earlier if PLL is locked
- "sleep first and then check the status"
https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/158998.html

ASoC: max98090: fix possible race conditions
- fix typo
https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/158966.html
- add more descriptions in commit message

Tzung-Bi Shih (3):
  ASoC: max98090: remove msleep in PLL unlocked workaround
  ASoC: max98090: exit workaround earlier if PLL is locked
  ASoC: max98090: fix possible race conditions

 sound/soc/codecs/max98090.c | 30 +++++++++++++++++++++---------
 sound/soc/codecs/max98090.h |  1 -
 2 files changed, 21 insertions(+), 10 deletions(-)

-- 
2.24.0.432.g9d3f5f5b63-goog

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[alsa-devel] [PATCH v2 1/3] ASoC: max98090: remove msleep in PLL unlocked workaround

[Tzung-Bi Shih]

It was observed Baytrail-based chromebooks could cause continuous PLL
unlocked when using playback stream and capture stream simultaneously.
Specifically, starting a capture stream after started a playback stream.
As a result, the audio data could corrupt or turn completely silent.

As the datasheet suggested, the maximum PLL lock time should be 7 msec.
The workaround resets the codec softly by toggling SHDN off and on if
PLL failed to lock for 10 msec.  Notably, there is no suggested hold
time for SHDN off.

On Baytrail-based chromebooks, it would easily happen continuous PLL
unlocked if there is a 10 msec delay between SHDN off and on.  Removes
the msleep().

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
---
 sound/soc/codecs/max98090.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index f6bf4cfbea23..12cb87c0d463 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -2114,10 +2114,16 @@ static void max98090_pll_work(struct work_struct *work)
 
 	dev_info_ratelimited(component->dev, "PLL unlocked\n");
 
+	/*
+	 * As the datasheet suggested, the maximum PLL lock time should be
+	 * 7 msec.  The workaround resets the codec softly by toggling SHDN
+	 * off and on if PLL failed to lock for 10 msec.  Notably, there is
+	 * no suggested hold time for SHDN off.
+	 */
+
 	/* Toggle shutdown OFF then ON */
 	snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
 			    M98090_SHDNN_MASK, 0);
-	msleep(10);
 	snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
 			    M98090_SHDNN_MASK, M98090_SHDNN_MASK);
 
-- 
2.24.0.432.g9d3f5f5b63-goog

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[alsa-devel] [PATCH v2 2/3] ASoC: max98090: exit workaround earlier if PLL is locked

[Tzung-Bi Shih]

According to the datasheet, PLL lock time typically takes 2 msec and
at most takes 7 msec.

Check the lock status every 1 msec and exit the workaround if PLL is
locked.

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
---
 sound/soc/codecs/max98090.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index 12cb87c0d463..f531e5a11bdd 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -2108,6 +2108,8 @@ static void max98090_pll_work(struct work_struct *work)
 	struct max98090_priv *max98090 =
 		container_of(work, struct max98090_priv, pll_work);
 	struct snd_soc_component *component = max98090->component;
+	unsigned int pll;
+	int i;
 
 	if (!snd_soc_component_is_active(component))
 		return;
@@ -2127,8 +2129,16 @@ static void max98090_pll_work(struct work_struct *work)
 	snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
 			    M98090_SHDNN_MASK, M98090_SHDNN_MASK);
 
-	/* Give PLL time to lock */
-	msleep(10);
+	for (i = 0; i < 10; ++i) {
+		/* Give PLL time to lock */
+		usleep_range(1000, 1200);
+
+		/* Check lock status */
+		pll = snd_soc_component_read32(
+				component, M98090_REG_DEVICE_STATUS);
+		if (!(pll & M98090_ULK_MASK))
+			break;
+	}
 }
 
 static void max98090_jack_work(struct work_struct *work)
-- 
2.24.0.432.g9d3f5f5b63-goog

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[alsa-devel] [PATCH v2 3/3] ASoC: max98090: fix possible race conditions

[Tzung-Bi Shih]

max98090_interrupt() and max98090_pll_work() run in 2 different threads.
There are 2 possible races:

Note: M98090_REG_DEVICE_STATUS = 0x01.
Note: ULK == 0, PLL is locked; ULK == 1, PLL is unlocked.

max98090_interrupt      max98090_pll_work
----------------------------------------------
schedule max98090_pll_work
                        restart max98090 codec
receive ULK INT
                        assert ULK == 0
schedule max98090_pll_work (1).

In the case (1), the PLL is locked but max98090_interrupt unnecessarily
schedules another max98090_pll_work.

max98090_interrupt      max98090_pll_work      max98090 codec
----------------------------------------------------------------------
                                               ULK = 1
receive ULK INT
read 0x01
                                               ULK = 0 (clear on read)
schedule max98090_pll_work
                        restart max98090 codec
                                               ULK = 1
receive ULK INT
read 0x01
                                               ULK = 0 (clear on read)
                        read 0x01
                        assert ULK == 0 (2).

In the case (2), both max98090_interrupt and max98090_pll_work read
the same clear-on-read register.  max98090_pll_work would falsely
thought PLL is locked.
Note: the case (2) race is introduced by the previous commit ("ASoC:
max98090: exit workaround earlier if PLL is locked") to check the status
and exit the loop earlier in max98090_pll_work.

There are 2 possible solution options:
A. turn off ULK interrupt before scheduling max98090_pll_work; and turn
on again before exiting max98090_pll_work.
B. remove the second thread of execution.

Option A cannot fix the case (2) race because it still has 2 threads
access the same clear-on-read register simultaneously.  Although we
could suppose the register is volatile and read the status via I2C could
be much slower than the hardware raises the bits.

Option B introduces a maximum 10~12 msec penalty delay in the interrupt
handler.  However, it could only punish the jack detection by extra
10~12 msec.

Adopts option B which is the better solution overall.

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
---
 sound/soc/codecs/max98090.c | 8 ++------
 sound/soc/codecs/max98090.h | 1 -
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index f531e5a11bdd..e46b6ada13b1 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -2103,10 +2103,8 @@ static void max98090_pll_det_disable_work(struct work_struct *work)
 			    M98090_IULK_MASK, 0);
 }
 
-static void max98090_pll_work(struct work_struct *work)
+static void max98090_pll_work(struct max98090_priv *max98090)
 {
-	struct max98090_priv *max98090 =
-		container_of(work, struct max98090_priv, pll_work);
 	struct snd_soc_component *component = max98090->component;
 	unsigned int pll;
 	int i;
@@ -2275,7 +2273,7 @@ static irqreturn_t max98090_interrupt(int irq, void *data)
 
 	if (active & M98090_ULK_MASK) {
 		dev_dbg(component->dev, "M98090_ULK_MASK\n");
-		schedule_work(&max98090->pll_work);
+		max98090_pll_work(max98090);
 	}
 
 	if (active & M98090_JDET_MASK) {
@@ -2438,7 +2436,6 @@ static int max98090_probe(struct snd_soc_component *component)
 			  max98090_pll_det_enable_work);
 	INIT_WORK(&max98090->pll_det_disable_work,
 		  max98090_pll_det_disable_work);
-	INIT_WORK(&max98090->pll_work, max98090_pll_work);
 
 	/* Enable jack detection */
 	snd_soc_component_write(component, M98090_REG_JACK_DETECT,
@@ -2491,7 +2488,6 @@ static void max98090_remove(struct snd_soc_component *component)
 	cancel_delayed_work_sync(&max98090->jack_work);
 	cancel_delayed_work_sync(&max98090->pll_det_enable_work);
 	cancel_work_sync(&max98090->pll_det_disable_work);
-	cancel_work_sync(&max98090->pll_work);
 	max98090->component = NULL;
 }
 
diff --git a/sound/soc/codecs/max98090.h b/sound/soc/codecs/max98090.h
index 57965cd678b4..a197114b0dad 100644
--- a/sound/soc/codecs/max98090.h
+++ b/sound/soc/codecs/max98090.h
@@ -1530,7 +1530,6 @@ struct max98090_priv {
 	struct delayed_work jack_work;
 	struct delayed_work pll_det_enable_work;
 	struct work_struct pll_det_disable_work;
-	struct work_struct pll_work;
 	struct snd_soc_jack *jack;
 	unsigned int dai_fmt;
 	int tdm_slots;
-- 
2.24.0.432.g9d3f5f5b63-goog

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Re: [alsa-devel] [PATCH v2 0/3] ASoC: max98090: fix PLL unlocked workaround-related

[Pierre-Louis Bossart]

On 11/22/19 1:31 AM, Tzung-Bi Shih wrote:
> This series is a follow up fix for the question:
> https://mailman.alsa-project.org/pipermail/alsa-devel/2019-October/157364.html

For the series

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

Hope this is the last time we see this PLL unlock error :-)


> 
> Changes from v1:
> ASoC: max98090: remove msleep in PLL unlocked workaround
> - add more comments
> https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/158969.html
> 
> ASoC: max98090: exit workaround earlier if PLL is locked
> - "sleep first and then check the status"
> https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/158998.html
> 
> ASoC: max98090: fix possible race conditions
> - fix typo
> https://mailman.alsa-project.org/pipermail/alsa-devel/2019-November/158966.html
> - add more descriptions in commit message
> 
> Tzung-Bi Shih (3):
>    ASoC: max98090: remove msleep in PLL unlocked workaround
>    ASoC: max98090: exit workaround earlier if PLL is locked
>    ASoC: max98090: fix possible race conditions
> 
>   sound/soc/codecs/max98090.c | 30 +++++++++++++++++++++---------
>   sound/soc/codecs/max98090.h |  1 -
>   2 files changed, 21 insertions(+), 10 deletions(-)
> 
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[alsa-devel] Applied "ASoC: max98090: fix possible race conditions" to the asoc tree

[Mark Brown]

The patch

   ASoC: max98090: fix possible race conditions

has been applied to the asoc tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-5.5

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

From 45dfbf56975994822cce00b7475732a49f8aefed Mon Sep 17 00:00:00 2001
From: Tzung-Bi Shih <tzungbi@google.com>
Date: Fri, 22 Nov 2019 15:31:14 +0800
Subject: [PATCH] ASoC: max98090: fix possible race conditions

max98090_interrupt() and max98090_pll_work() run in 2 different threads.
There are 2 possible races:

Note: M98090_REG_DEVICE_STATUS = 0x01.
Note: ULK == 0, PLL is locked; ULK == 1, PLL is unlocked.

max98090_interrupt      max98090_pll_work
----------------------------------------------
schedule max98090_pll_work
                        restart max98090 codec
receive ULK INT
                        assert ULK == 0
schedule max98090_pll_work (1).

In the case (1), the PLL is locked but max98090_interrupt unnecessarily
schedules another max98090_pll_work.

max98090_interrupt      max98090_pll_work      max98090 codec
----------------------------------------------------------------------
                                               ULK = 1
receive ULK INT
read 0x01
                                               ULK = 0 (clear on read)
schedule max98090_pll_work
                        restart max98090 codec
                                               ULK = 1
receive ULK INT
read 0x01
                                               ULK = 0 (clear on read)
                        read 0x01
                        assert ULK == 0 (2).

In the case (2), both max98090_interrupt and max98090_pll_work read
the same clear-on-read register.  max98090_pll_work would falsely
thought PLL is locked.
Note: the case (2) race is introduced by the previous commit ("ASoC:
max98090: exit workaround earlier if PLL is locked") to check the status
and exit the loop earlier in max98090_pll_work.

There are 2 possible solution options:
A. turn off ULK interrupt before scheduling max98090_pll_work; and turn
on again before exiting max98090_pll_work.
B. remove the second thread of execution.

Option A cannot fix the case (2) race because it still has 2 threads
access the same clear-on-read register simultaneously.  Although we
could suppose the register is volatile and read the status via I2C could
be much slower than the hardware raises the bits.

Option B introduces a maximum 10~12 msec penalty delay in the interrupt
handler.  However, it could only punish the jack detection by extra
10~12 msec.

Adopts option B which is the better solution overall.

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20191122073114.219945-4-tzungbi@google.com
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 sound/soc/codecs/max98090.c | 8 ++------
 sound/soc/codecs/max98090.h | 1 -
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index f531e5a11bdd..e46b6ada13b1 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -2103,10 +2103,8 @@ static void max98090_pll_det_disable_work(struct work_struct *work)
 			    M98090_IULK_MASK, 0);
 }
 
-static void max98090_pll_work(struct work_struct *work)
+static void max98090_pll_work(struct max98090_priv *max98090)
 {
-	struct max98090_priv *max98090 =
-		container_of(work, struct max98090_priv, pll_work);
 	struct snd_soc_component *component = max98090->component;
 	unsigned int pll;
 	int i;
@@ -2275,7 +2273,7 @@ static irqreturn_t max98090_interrupt(int irq, void *data)
 
 	if (active & M98090_ULK_MASK) {
 		dev_dbg(component->dev, "M98090_ULK_MASK\n");
-		schedule_work(&max98090->pll_work);
+		max98090_pll_work(max98090);
 	}
 
 	if (active & M98090_JDET_MASK) {
@@ -2438,7 +2436,6 @@ static int max98090_probe(struct snd_soc_component *component)
 			  max98090_pll_det_enable_work);
 	INIT_WORK(&max98090->pll_det_disable_work,
 		  max98090_pll_det_disable_work);
-	INIT_WORK(&max98090->pll_work, max98090_pll_work);
 
 	/* Enable jack detection */
 	snd_soc_component_write(component, M98090_REG_JACK_DETECT,
@@ -2491,7 +2488,6 @@ static void max98090_remove(struct snd_soc_component *component)
 	cancel_delayed_work_sync(&max98090->jack_work);
 	cancel_delayed_work_sync(&max98090->pll_det_enable_work);
 	cancel_work_sync(&max98090->pll_det_disable_work);
-	cancel_work_sync(&max98090->pll_work);
 	max98090->component = NULL;
 }
 
diff --git a/sound/soc/codecs/max98090.h b/sound/soc/codecs/max98090.h
index 57965cd678b4..a197114b0dad 100644
--- a/sound/soc/codecs/max98090.h
+++ b/sound/soc/codecs/max98090.h
@@ -1530,7 +1530,6 @@ struct max98090_priv {
 	struct delayed_work jack_work;
 	struct delayed_work pll_det_enable_work;
 	struct work_struct pll_det_disable_work;
-	struct work_struct pll_work;
 	struct snd_soc_jack *jack;
 	unsigned int dai_fmt;
 	int tdm_slots;
-- 
2.20.1

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[alsa-devel] Applied "ASoC: max98090: exit workaround earlier if PLL is locked" to the asoc tree

[Mark Brown]

The patch

   ASoC: max98090: exit workaround earlier if PLL is locked

has been applied to the asoc tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-5.5

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

From 6f49919d11690a9b5614445ba30fde18083fdd63 Mon Sep 17 00:00:00 2001
From: Tzung-Bi Shih <tzungbi@google.com>
Date: Fri, 22 Nov 2019 15:31:13 +0800
Subject: [PATCH] ASoC: max98090: exit workaround earlier if PLL is locked

According to the datasheet, PLL lock time typically takes 2 msec and
at most takes 7 msec.

Check the lock status every 1 msec and exit the workaround if PLL is
locked.

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20191122073114.219945-3-tzungbi@google.com
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 sound/soc/codecs/max98090.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index 12cb87c0d463..f531e5a11bdd 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -2108,6 +2108,8 @@ static void max98090_pll_work(struct work_struct *work)
 	struct max98090_priv *max98090 =
 		container_of(work, struct max98090_priv, pll_work);
 	struct snd_soc_component *component = max98090->component;
+	unsigned int pll;
+	int i;
 
 	if (!snd_soc_component_is_active(component))
 		return;
@@ -2127,8 +2129,16 @@ static void max98090_pll_work(struct work_struct *work)
 	snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
 			    M98090_SHDNN_MASK, M98090_SHDNN_MASK);
 
-	/* Give PLL time to lock */
-	msleep(10);
+	for (i = 0; i < 10; ++i) {
+		/* Give PLL time to lock */
+		usleep_range(1000, 1200);
+
+		/* Check lock status */
+		pll = snd_soc_component_read32(
+				component, M98090_REG_DEVICE_STATUS);
+		if (!(pll & M98090_ULK_MASK))
+			break;
+	}
 }
 
 static void max98090_jack_work(struct work_struct *work)
-- 
2.20.1

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[alsa-devel] Applied "ASoC: max98090: remove msleep in PLL unlocked workaround" to the asoc tree

[Mark Brown]

The patch

   ASoC: max98090: remove msleep in PLL unlocked workaround

has been applied to the asoc tree at

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-5.5

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

From acb874a7c049ec49d8fc66c893170fb42c01bdf7 Mon Sep 17 00:00:00 2001
From: Tzung-Bi Shih <tzungbi@google.com>
Date: Fri, 22 Nov 2019 15:31:12 +0800
Subject: [PATCH] ASoC: max98090: remove msleep in PLL unlocked workaround

It was observed Baytrail-based chromebooks could cause continuous PLL
unlocked when using playback stream and capture stream simultaneously.
Specifically, starting a capture stream after started a playback stream.
As a result, the audio data could corrupt or turn completely silent.

As the datasheet suggested, the maximum PLL lock time should be 7 msec.
The workaround resets the codec softly by toggling SHDN off and on if
PLL failed to lock for 10 msec.  Notably, there is no suggested hold
time for SHDN off.

On Baytrail-based chromebooks, it would easily happen continuous PLL
unlocked if there is a 10 msec delay between SHDN off and on.  Removes
the msleep().

Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20191122073114.219945-2-tzungbi@google.com
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 sound/soc/codecs/max98090.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c
index f6bf4cfbea23..12cb87c0d463 100644
--- a/sound/soc/codecs/max98090.c
+++ b/sound/soc/codecs/max98090.c
@@ -2114,10 +2114,16 @@ static void max98090_pll_work(struct work_struct *work)
 
 	dev_info_ratelimited(component->dev, "PLL unlocked\n");
 
+	/*
+	 * As the datasheet suggested, the maximum PLL lock time should be
+	 * 7 msec.  The workaround resets the codec softly by toggling SHDN
+	 * off and on if PLL failed to lock for 10 msec.  Notably, there is
+	 * no suggested hold time for SHDN off.
+	 */
+
 	/* Toggle shutdown OFF then ON */
 	snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
 			    M98090_SHDNN_MASK, 0);
-	msleep(10);
 	snd_soc_component_update_bits(component, M98090_REG_DEVICE_SHUTDOWN,
 			    M98090_SHDNN_MASK, M98090_SHDNN_MASK);
 
-- 
2.20.1

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