[PATCH] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[PATCH] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Alexandru Ardelean]

From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock on the device's state structure.

The patch also does a minor whitespace change to align the 'lock' with the
'common' field via tabs.

Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/iio/dac/stm32-dac.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
index 092c796fa3d9..fc636812c17e 100644
--- a/drivers/iio/dac/stm32-dac.c
+++ b/drivers/iio/dac/stm32-dac.c
@@ -26,9 +26,11 @@
 /**
  * struct stm32_dac - private data of DAC driver
  * @common:		reference to DAC common data
+ * @lock:		lock to protect the data buffer during regmap ops
  */
 struct stm32_dac {
-	struct stm32_dac_common *common;
+	struct stm32_dac_common	*common;
+	struct mutex		lock;
 };
 
 static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
@@ -58,10 +60,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 	int ret;
 
 	/* already enabled / disabled ? */
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&dac->lock);
 	ret = stm32_dac_is_enabled(indio_dev, ch);
 	if (ret < 0 || enable == !!ret) {
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&dac->lock);
 		return ret < 0 ? ret : 0;
 	}
 
@@ -69,13 +71,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 		ret = pm_runtime_get_sync(dev);
 		if (ret < 0) {
 			pm_runtime_put_noidle(dev);
-			mutex_unlock(&indio_dev->mlock);
+			mutex_unlock(&dac->lock);
 			return ret;
 		}
 	}
 
 	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&dac->lock);
 	if (ret < 0) {
 		dev_err(&indio_dev->dev, "%s failed\n", en ?
 			"Enable" : "Disable");
@@ -327,6 +329,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
 	indio_dev->info = &stm32_dac_iio_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
+	mutex_init(&dac->lock);
+
 	ret = stm32_dac_chan_of_init(indio_dev);
 	if (ret < 0)
 		return ret;
-- 
2.25.1

Re: [PATCH] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Fabrice Gasnier]

On 8/26/20 8:38 AM, Alexandru Ardelean wrote:
> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> 
> As part of the general cleanup of indio_dev->mlock, this change replaces
> it with a local lock on the device's state structure.
> 
> The patch also does a minor whitespace change to align the 'lock' with the
> 'common' field via tabs.
> 
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---
>  drivers/iio/dac/stm32-dac.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> index 092c796fa3d9..fc636812c17e 100644
> --- a/drivers/iio/dac/stm32-dac.c
> +++ b/drivers/iio/dac/stm32-dac.c
> @@ -26,9 +26,11 @@
>  /**
>   * struct stm32_dac - private data of DAC driver
>   * @common:		reference to DAC common data
> + * @lock:		lock to protect the data buffer during regmap ops

Hi Alexandru,

I think the same patch has been sent by Sergiu already [1].
Jonathan and I had a minor comment at that time: E.g. could you please
update the comment ?

[1] https://lkml.org/lkml/2020/5/18/254

>   */
>  struct stm32_dac {
> -	struct stm32_dac_common *common;
> +	struct stm32_dac_common	*common;

Is above change needed?

Best Regards,
Fabrice

> +	struct mutex		lock;
>  };
>  
>  static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
> @@ -58,10 +60,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>  	int ret;
>  
>  	/* already enabled / disabled ? */
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&dac->lock);
>  	ret = stm32_dac_is_enabled(indio_dev, ch);
>  	if (ret < 0 || enable == !!ret) {
> -		mutex_unlock(&indio_dev->mlock);
> +		mutex_unlock(&dac->lock);
>  		return ret < 0 ? ret : 0;
>  	}
>  
> @@ -69,13 +71,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>  		ret = pm_runtime_get_sync(dev);
>  		if (ret < 0) {
>  			pm_runtime_put_noidle(dev);
> -			mutex_unlock(&indio_dev->mlock);
> +			mutex_unlock(&dac->lock);
>  			return ret;
>  		}
>  	}
>  
>  	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&dac->lock);
>  	if (ret < 0) {
>  		dev_err(&indio_dev->dev, "%s failed\n", en ?
>  			"Enable" : "Disable");
> @@ -327,6 +329,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
>  	indio_dev->info = &stm32_dac_iio_info;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  
> +	mutex_init(&dac->lock);
> +
>  	ret = stm32_dac_chan_of_init(indio_dev);
>  	if (ret < 0)
>  		return ret;
> 

Re: [PATCH] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Alexandru Ardelean]

On Wed, Aug 26, 2020 at 12:01 PM Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
>
> On 8/26/20 8:38 AM, Alexandru Ardelean wrote:
> > From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> >
> > As part of the general cleanup of indio_dev->mlock, this change replaces
> > it with a local lock on the device's state structure.
> >
> > The patch also does a minor whitespace change to align the 'lock' with the
> > 'common' field via tabs.
> >
> > Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > ---
> >  drivers/iio/dac/stm32-dac.c | 14 +++++++++-----
> >  1 file changed, 9 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> > index 092c796fa3d9..fc636812c17e 100644
> > --- a/drivers/iio/dac/stm32-dac.c
> > +++ b/drivers/iio/dac/stm32-dac.c
> > @@ -26,9 +26,11 @@
> >  /**
> >   * struct stm32_dac - private data of DAC driver
> >   * @common:          reference to DAC common data
> > + * @lock:            lock to protect the data buffer during regmap ops
>
> Hi Alexandru,
>
> I think the same patch has been sent by Sergiu already [1].
> Jonathan and I had a minor comment at that time: E.g. could you please
> update the comment ?

Oh.
My bad. I didn't follow the discussion closely.
Will send a V2.

>
> [1] https://lkml.org/lkml/2020/5/18/254
>
> >   */
> >  struct stm32_dac {
> > -     struct stm32_dac_common *common;
> > +     struct stm32_dac_common *common;
>
> Is above change needed?

No.
I can remove it.

Thanks
Alex

>
> Best Regards,
> Fabrice
>
> > +     struct mutex            lock;
> >  };
> >
> >  static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
> > @@ -58,10 +60,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
> >       int ret;
> >
> >       /* already enabled / disabled ? */
> > -     mutex_lock(&indio_dev->mlock);
> > +     mutex_lock(&dac->lock);
> >       ret = stm32_dac_is_enabled(indio_dev, ch);
> >       if (ret < 0 || enable == !!ret) {
> > -             mutex_unlock(&indio_dev->mlock);
> > +             mutex_unlock(&dac->lock);
> >               return ret < 0 ? ret : 0;
> >       }
> >
> > @@ -69,13 +71,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
> >               ret = pm_runtime_get_sync(dev);
> >               if (ret < 0) {
> >                       pm_runtime_put_noidle(dev);
> > -                     mutex_unlock(&indio_dev->mlock);
> > +                     mutex_unlock(&dac->lock);
> >                       return ret;
> >               }
> >       }
> >
> >       ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
> > -     mutex_unlock(&indio_dev->mlock);
> > +     mutex_unlock(&dac->lock);
> >       if (ret < 0) {
> >               dev_err(&indio_dev->dev, "%s failed\n", en ?
> >                       "Enable" : "Disable");
> > @@ -327,6 +329,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
> >       indio_dev->info = &stm32_dac_iio_info;
> >       indio_dev->modes = INDIO_DIRECT_MODE;
> >
> > +     mutex_init(&dac->lock);
> > +
> >       ret = stm32_dac_chan_of_init(indio_dev);
> >       if (ret < 0)
> >               return ret;
> >

[PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Alexandru Ardelean]

From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock. The lock protects against potential races when
reading the CR reg and then updating, so that the state of pm_runtime
is consistent between the two operations.

Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/iio/dac/stm32-dac.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
index 092c796fa3d9..7a8aed476850 100644
--- a/drivers/iio/dac/stm32-dac.c
+++ b/drivers/iio/dac/stm32-dac.c
@@ -26,9 +26,11 @@
 /**
  * struct stm32_dac - private data of DAC driver
  * @common:		reference to DAC common data
+ * @lock:		lock to protect the data buffer during regmap ops
  */
 struct stm32_dac {
 	struct stm32_dac_common *common;
+	struct mutex		lock;
 };
 
 static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
@@ -58,10 +60,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 	int ret;
 
 	/* already enabled / disabled ? */
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&dac->lock);
 	ret = stm32_dac_is_enabled(indio_dev, ch);
 	if (ret < 0 || enable == !!ret) {
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&dac->lock);
 		return ret < 0 ? ret : 0;
 	}
 
@@ -69,13 +71,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 		ret = pm_runtime_get_sync(dev);
 		if (ret < 0) {
 			pm_runtime_put_noidle(dev);
-			mutex_unlock(&indio_dev->mlock);
+			mutex_unlock(&dac->lock);
 			return ret;
 		}
 	}
 
 	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&dac->lock);
 	if (ret < 0) {
 		dev_err(&indio_dev->dev, "%s failed\n", en ?
 			"Enable" : "Disable");
@@ -327,6 +329,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
 	indio_dev->info = &stm32_dac_iio_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
+	mutex_init(&dac->lock);
+
 	ret = stm32_dac_chan_of_init(indio_dev);
 	if (ret < 0)
 		return ret;
-- 
2.25.1

Re: [PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Alexandru Ardelean]

On Wed, Aug 26, 2020 at 3:03 PM Alexandru Ardelean
<alexandru.ardelean@analog.com> wrote:
>
> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
>
> As part of the general cleanup of indio_dev->mlock, this change replaces
> it with a local lock. The lock protects against potential races when
> reading the CR reg and then updating, so that the state of pm_runtime
> is consistent between the two operations.
>
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---

Forgot the changelog here.
Apologies.

Changelog v1 -> v2:
* removed whitespace change for 'common' field
* updated comment about the lock usage

>  drivers/iio/dac/stm32-dac.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> index 092c796fa3d9..7a8aed476850 100644
> --- a/drivers/iio/dac/stm32-dac.c
> +++ b/drivers/iio/dac/stm32-dac.c
> @@ -26,9 +26,11 @@
>  /**
>   * struct stm32_dac - private data of DAC driver
>   * @common:            reference to DAC common data
> + * @lock:              lock to protect the data buffer during regmap ops
>   */
>  struct stm32_dac {
>         struct stm32_dac_common *common;
> +       struct mutex            lock;
>  };
>
>  static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
> @@ -58,10 +60,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>         int ret;
>
>         /* already enabled / disabled ? */
> -       mutex_lock(&indio_dev->mlock);
> +       mutex_lock(&dac->lock);
>         ret = stm32_dac_is_enabled(indio_dev, ch);
>         if (ret < 0 || enable == !!ret) {
> -               mutex_unlock(&indio_dev->mlock);
> +               mutex_unlock(&dac->lock);
>                 return ret < 0 ? ret : 0;
>         }
>
> @@ -69,13 +71,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>                 ret = pm_runtime_get_sync(dev);
>                 if (ret < 0) {
>                         pm_runtime_put_noidle(dev);
> -                       mutex_unlock(&indio_dev->mlock);
> +                       mutex_unlock(&dac->lock);
>                         return ret;
>                 }
>         }
>
>         ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
> -       mutex_unlock(&indio_dev->mlock);
> +       mutex_unlock(&dac->lock);
>         if (ret < 0) {
>                 dev_err(&indio_dev->dev, "%s failed\n", en ?
>                         "Enable" : "Disable");
> @@ -327,6 +329,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
>         indio_dev->info = &stm32_dac_iio_info;
>         indio_dev->modes = INDIO_DIRECT_MODE;
>
> +       mutex_init(&dac->lock);
> +
>         ret = stm32_dac_chan_of_init(indio_dev);
>         if (ret < 0)
>                 return ret;
> --
> 2.25.1
>

Re: [PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Fabrice Gasnier]

On 8/27/20 10:55 AM, Alexandru Ardelean wrote:
> On Wed, Aug 26, 2020 at 3:03 PM Alexandru Ardelean
> <alexandru.ardelean@analog.com> wrote:
>> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
>>
>> As part of the general cleanup of indio_dev->mlock, this change replaces
>> it with a local lock. The lock protects against potential races when
>> reading the CR reg and then updating, so that the state of pm_runtime
>> is consistent between the two operations.
>>
>> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
>> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
>> ---
> Forgot the changelog here.
> Apologies.
> 
> Changelog v1 -> v2:
> * removed whitespace change for 'common' field
> * updated comment about the lock usage

Hi Alexandru,

Sorry if I missed it... is there an update on the comment :-) ?

Best Regards,
Fabrice
> 
>>  drivers/iio/dac/stm32-dac.c | 12 ++++++++----
>>  1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
>> index 092c796fa3d9..7a8aed476850 100644
>> --- a/drivers/iio/dac/stm32-dac.c
>> +++ b/drivers/iio/dac/stm32-dac.c
>> @@ -26,9 +26,11 @@
>>  /**
>>   * struct stm32_dac - private data of DAC driver
>>   * @common:            reference to DAC common data
>> + * @lock:              lock to protect the data buffer during regmap ops
>>   */
>>  struct stm32_dac {
>>         struct stm32_dac_common *common;
>> +       struct mutex            lock;
>>  };

Re: [PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Alexandru Ardelean]

On Thu, Aug 27, 2020 at 12:03 PM Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
>
> On 8/27/20 10:55 AM, Alexandru Ardelean wrote:
> > On Wed, Aug 26, 2020 at 3:03 PM Alexandru Ardelean
> > <alexandru.ardelean@analog.com> wrote:
> >> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> >>
> >> As part of the general cleanup of indio_dev->mlock, this change replaces
> >> it with a local lock. The lock protects against potential races when
> >> reading the CR reg and then updating, so that the state of pm_runtime
> >> is consistent between the two operations.
> >>
> >> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> >> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> >> ---
> > Forgot the changelog here.
> > Apologies.
> >
> > Changelog v1 -> v2:
> > * removed whitespace change for 'common' field
> > * updated comment about the lock usage
>
> Hi Alexandru,
>
> Sorry if I missed it... is there an update on the comment :-) ?

For a moment there, I thought I didn't.
GMail's threading is confusing.

----------------------------------------------------------------------------
As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock. The lock protects against potential races when
reading the CR reg and then updating, so that the state of pm_runtime
is consistent between the two operations.
----------------------------------------------------------------------------

>
> Best Regards,
> Fabrice
> >
> >>  drivers/iio/dac/stm32-dac.c | 12 ++++++++----
> >>  1 file changed, 8 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> >> index 092c796fa3d9..7a8aed476850 100644
> >> --- a/drivers/iio/dac/stm32-dac.c
> >> +++ b/drivers/iio/dac/stm32-dac.c
> >> @@ -26,9 +26,11 @@
> >>  /**
> >>   * struct stm32_dac - private data of DAC driver
> >>   * @common:            reference to DAC common data
> >> + * @lock:              lock to protect the data buffer during regmap ops
> >>   */
> >>  struct stm32_dac {
> >>         struct stm32_dac_common *common;
> >> +       struct mutex            lock;
> >>  };

Re: [PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Jonathan Cameron]

On Thu, 27 Aug 2020 13:00:36 +0300
Alexandru Ardelean <ardeleanalex@gmail.com> wrote:

> On Thu, Aug 27, 2020 at 12:03 PM Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
> >
> > On 8/27/20 10:55 AM, Alexandru Ardelean wrote:  
> > > On Wed, Aug 26, 2020 at 3:03 PM Alexandru Ardelean
> > > <alexandru.ardelean@analog.com> wrote:  
> > >> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > >>
> > >> As part of the general cleanup of indio_dev->mlock, this change replaces
> > >> it with a local lock. The lock protects against potential races when
> > >> reading the CR reg and then updating, so that the state of pm_runtime
> > >> is consistent between the two operations.
> > >>
> > >> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > >> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > >> ---  
> > > Forgot the changelog here.
> > > Apologies.
> > >
> > > Changelog v1 -> v2:
> > > * removed whitespace change for 'common' field
> > > * updated comment about the lock usage  
> >
> > Hi Alexandru,
> >
> > Sorry if I missed it... is there an update on the comment :-) ?  
> 
> For a moment there, I thought I didn't.
> GMail's threading is confusing.
> 
> ----------------------------------------------------------------------------
> As part of the general cleanup of indio_dev->mlock, this change replaces
> it with a local lock. The lock protects against potential races when
> reading the CR reg and then updating, so that the state of pm_runtime
> is consistent between the two operations.
> ----------------------------------------------------------------------------
I think this got confused...

see below.


> 
> >
> > Best Regards,
> > Fabrice  
> > >  
> > >>  drivers/iio/dac/stm32-dac.c | 12 ++++++++----
> > >>  1 file changed, 8 insertions(+), 4 deletions(-)
> > >>
> > >> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> > >> index 092c796fa3d9..7a8aed476850 100644
> > >> --- a/drivers/iio/dac/stm32-dac.c
> > >> +++ b/drivers/iio/dac/stm32-dac.c
> > >> @@ -26,9 +26,11 @@
> > >>  /**
> > >>   * struct stm32_dac - private data of DAC driver
> > >>   * @common:            reference to DAC common data
> > >> + * @lock:              lock to protect the data buffer during regmap ops

The original comment was:


In this particular case I'm not sure that's what mlock was being used for.
I think it's about avoiding races around checking if powered down and
actually doing it.

And Fabrice's reply:

Hi Sergiu,

Indeed, purpose is to protect against a race here when reading CR, and
updating it via regmap (this also makes the subsequent pm_runtime calls
to be balanced based on this).
(Side note: there is no data buffer involved for the DAC.)
Could you please update the comment ?

Thanks,
Fabrice

> > >>   */
> > >>  struct stm32_dac {
> > >>         struct stm32_dac_common *common;
> > >> +       struct mutex            lock;
> > >>  };  

Re: [PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Alexandru Ardelean]

On Sat, Aug 29, 2020 at 6:46 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Thu, 27 Aug 2020 13:00:36 +0300
> Alexandru Ardelean <ardeleanalex@gmail.com> wrote:
>
> > On Thu, Aug 27, 2020 at 12:03 PM Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
> > >
> > > On 8/27/20 10:55 AM, Alexandru Ardelean wrote:
> > > > On Wed, Aug 26, 2020 at 3:03 PM Alexandru Ardelean
> > > > <alexandru.ardelean@analog.com> wrote:
> > > >> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > > >>
> > > >> As part of the general cleanup of indio_dev->mlock, this change replaces
> > > >> it with a local lock. The lock protects against potential races when
> > > >> reading the CR reg and then updating, so that the state of pm_runtime
> > > >> is consistent between the two operations.
> > > >>
> > > >> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > > >> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > > >> ---
> > > > Forgot the changelog here.
> > > > Apologies.
> > > >
> > > > Changelog v1 -> v2:
> > > > * removed whitespace change for 'common' field
> > > > * updated comment about the lock usage
> > >
> > > Hi Alexandru,
> > >
> > > Sorry if I missed it... is there an update on the comment :-) ?
> >
> > For a moment there, I thought I didn't.
> > GMail's threading is confusing.
> >
> > ----------------------------------------------------------------------------
> > As part of the general cleanup of indio_dev->mlock, this change replaces
> > it with a local lock. The lock protects against potential races when
> > reading the CR reg and then updating, so that the state of pm_runtime
> > is consistent between the two operations.
> > ----------------------------------------------------------------------------
> I think this got confused...
>
> see below.
>
>
> >
> > >
> > > Best Regards,
> > > Fabrice
> > > >
> > > >>  drivers/iio/dac/stm32-dac.c | 12 ++++++++----
> > > >>  1 file changed, 8 insertions(+), 4 deletions(-)
> > > >>
> > > >> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> > > >> index 092c796fa3d9..7a8aed476850 100644
> > > >> --- a/drivers/iio/dac/stm32-dac.c
> > > >> +++ b/drivers/iio/dac/stm32-dac.c
> > > >> @@ -26,9 +26,11 @@
> > > >>  /**
> > > >>   * struct stm32_dac - private data of DAC driver
> > > >>   * @common:            reference to DAC common data
> > > >> + * @lock:              lock to protect the data buffer during regmap ops

oh, silly me;
it's about this comment;
will re-spin

>
> The original comment was:
>
>
> In this particular case I'm not sure that's what mlock was being used for.
> I think it's about avoiding races around checking if powered down and
> actually doing it.
>
> And Fabrice's reply:
>
> Hi Sergiu,
>
> Indeed, purpose is to protect against a race here when reading CR, and
> updating it via regmap (this also makes the subsequent pm_runtime calls
> to be balanced based on this).
> (Side note: there is no data buffer involved for the DAC.)
> Could you please update the comment ?
>
> Thanks,
> Fabrice
>
> > > >>   */
> > > >>  struct stm32_dac {
> > > >>         struct stm32_dac_common *common;
> > > >> +       struct mutex            lock;
> > > >>  };
>

[PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Alexandru Ardelean]

From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>

As part of the general cleanup of indio_dev->mlock, this change replaces
it with a local lock. The lock protects against potential races when
reading the CR reg and then updating, so that the state of pm_runtime
is consistent between the two operations.

This is part of a bigger cleanup.
Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/

Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
 drivers/iio/dac/stm32-dac.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
index 092c796fa3d9..12dec68c16f7 100644
--- a/drivers/iio/dac/stm32-dac.c
+++ b/drivers/iio/dac/stm32-dac.c
@@ -26,9 +26,12 @@
 /**
  * struct stm32_dac - private data of DAC driver
  * @common:		reference to DAC common data
+ * @lock:		lock to protect against potential races when reading
+ *			and update CR, to keep it in sync with pm_runtime
  */
 struct stm32_dac {
 	struct stm32_dac_common *common;
+	struct mutex		lock;
 };
 
 static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
@@ -58,10 +61,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 	int ret;
 
 	/* already enabled / disabled ? */
-	mutex_lock(&indio_dev->mlock);
+	mutex_lock(&dac->lock);
 	ret = stm32_dac_is_enabled(indio_dev, ch);
 	if (ret < 0 || enable == !!ret) {
-		mutex_unlock(&indio_dev->mlock);
+		mutex_unlock(&dac->lock);
 		return ret < 0 ? ret : 0;
 	}
 
@@ -69,13 +72,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
 		ret = pm_runtime_get_sync(dev);
 		if (ret < 0) {
 			pm_runtime_put_noidle(dev);
-			mutex_unlock(&indio_dev->mlock);
+			mutex_unlock(&dac->lock);
 			return ret;
 		}
 	}
 
 	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
-	mutex_unlock(&indio_dev->mlock);
+	mutex_unlock(&dac->lock);
 	if (ret < 0) {
 		dev_err(&indio_dev->dev, "%s failed\n", en ?
 			"Enable" : "Disable");
@@ -327,6 +330,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
 	indio_dev->info = &stm32_dac_iio_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
+	mutex_init(&dac->lock);
+
 	ret = stm32_dac_chan_of_init(indio_dev);
 	if (ret < 0)
 		return ret;
-- 
2.17.1

Re: [PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Fabrice Gasnier]

On 9/16/20 11:23 AM, Alexandru Ardelean wrote:
> From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> 
> As part of the general cleanup of indio_dev->mlock, this change replaces
> it with a local lock. The lock protects against potential races when
> reading the CR reg and then updating, so that the state of pm_runtime
> is consistent between the two operations.
> 
> This is part of a bigger cleanup.
> Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/
> 
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> ---
>  drivers/iio/dac/stm32-dac.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)

Hi Alexandru,

Many thanks for this updated patch,

Reviewed-by: Fabrice Gasnier <fabrice.gasnier@st.com>

Best regards,
Fabrice

> 
> diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> index 092c796fa3d9..12dec68c16f7 100644
> --- a/drivers/iio/dac/stm32-dac.c
> +++ b/drivers/iio/dac/stm32-dac.c
> @@ -26,9 +26,12 @@
>  /**
>   * struct stm32_dac - private data of DAC driver
>   * @common:		reference to DAC common data
> + * @lock:		lock to protect against potential races when reading
> + *			and update CR, to keep it in sync with pm_runtime
>   */
>  struct stm32_dac {
>  	struct stm32_dac_common *common;
> +	struct mutex		lock;
>  };
>  
>  static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
> @@ -58,10 +61,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>  	int ret;
>  
>  	/* already enabled / disabled ? */
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&dac->lock);
>  	ret = stm32_dac_is_enabled(indio_dev, ch);
>  	if (ret < 0 || enable == !!ret) {
> -		mutex_unlock(&indio_dev->mlock);
> +		mutex_unlock(&dac->lock);
>  		return ret < 0 ? ret : 0;
>  	}
>  
> @@ -69,13 +72,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
>  		ret = pm_runtime_get_sync(dev);
>  		if (ret < 0) {
>  			pm_runtime_put_noidle(dev);
> -			mutex_unlock(&indio_dev->mlock);
> +			mutex_unlock(&dac->lock);
>  			return ret;
>  		}
>  	}
>  
>  	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&dac->lock);
>  	if (ret < 0) {
>  		dev_err(&indio_dev->dev, "%s failed\n", en ?
>  			"Enable" : "Disable");
> @@ -327,6 +330,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
>  	indio_dev->info = &stm32_dac_iio_info;
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  
> +	mutex_init(&dac->lock);
> +
>  	ret = stm32_dac_chan_of_init(indio_dev);
>  	if (ret < 0)
>  		return ret;
> 

Re: [PATCH v2] iio: stm32-dac: Replace indio_dev->mlock with own device lock

[Jonathan Cameron]

On Wed, 16 Sep 2020 12:18:02 +0200
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> On 9/16/20 11:23 AM, Alexandru Ardelean wrote:
> > From: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > 
> > As part of the general cleanup of indio_dev->mlock, this change replaces
> > it with a local lock. The lock protects against potential races when
> > reading the CR reg and then updating, so that the state of pm_runtime
> > is consistent between the two operations.
> > 
> > This is part of a bigger cleanup.
> > Link: https://lore.kernel.org/linux-iio/CA+U=Dsoo6YABe5ODLp+eFNPGFDjk5ZeQEceGkqjxXcVEhLWubw@mail.gmail.com/
> > 
> > Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
> > Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
> > ---
> >  drivers/iio/dac/stm32-dac.c | 13 +++++++++----
> >  1 file changed, 9 insertions(+), 4 deletions(-)  
> 
> Hi Alexandru,
> 
> Many thanks for this updated patch,
> 
> Reviewed-by: Fabrice Gasnier <fabrice.gasnier@st.com>

Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to poke at it.

Thanks,

Jonathan

> 
> Best regards,
> Fabrice
> 
> > 
> > diff --git a/drivers/iio/dac/stm32-dac.c b/drivers/iio/dac/stm32-dac.c
> > index 092c796fa3d9..12dec68c16f7 100644
> > --- a/drivers/iio/dac/stm32-dac.c
> > +++ b/drivers/iio/dac/stm32-dac.c
> > @@ -26,9 +26,12 @@
> >  /**
> >   * struct stm32_dac - private data of DAC driver
> >   * @common:		reference to DAC common data
> > + * @lock:		lock to protect against potential races when reading
> > + *			and update CR, to keep it in sync with pm_runtime
> >   */
> >  struct stm32_dac {
> >  	struct stm32_dac_common *common;
> > +	struct mutex		lock;
> >  };
> >  
> >  static int stm32_dac_is_enabled(struct iio_dev *indio_dev, int channel)
> > @@ -58,10 +61,10 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
> >  	int ret;
> >  
> >  	/* already enabled / disabled ? */
> > -	mutex_lock(&indio_dev->mlock);
> > +	mutex_lock(&dac->lock);
> >  	ret = stm32_dac_is_enabled(indio_dev, ch);
> >  	if (ret < 0 || enable == !!ret) {
> > -		mutex_unlock(&indio_dev->mlock);
> > +		mutex_unlock(&dac->lock);
> >  		return ret < 0 ? ret : 0;
> >  	}
> >  
> > @@ -69,13 +72,13 @@ static int stm32_dac_set_enable_state(struct iio_dev *indio_dev, int ch,
> >  		ret = pm_runtime_get_sync(dev);
> >  		if (ret < 0) {
> >  			pm_runtime_put_noidle(dev);
> > -			mutex_unlock(&indio_dev->mlock);
> > +			mutex_unlock(&dac->lock);
> >  			return ret;
> >  		}
> >  	}
> >  
> >  	ret = regmap_update_bits(dac->common->regmap, STM32_DAC_CR, msk, en);
> > -	mutex_unlock(&indio_dev->mlock);
> > +	mutex_unlock(&dac->lock);
> >  	if (ret < 0) {
> >  		dev_err(&indio_dev->dev, "%s failed\n", en ?
> >  			"Enable" : "Disable");
> > @@ -327,6 +330,8 @@ static int stm32_dac_probe(struct platform_device *pdev)
> >  	indio_dev->info = &stm32_dac_iio_info;
> >  	indio_dev->modes = INDIO_DIRECT_MODE;
> >  
> > +	mutex_init(&dac->lock);
> > +
> >  	ret = stm32_dac_chan_of_init(indio_dev);
> >  	if (ret < 0)
> >  		return ret;
> >