iio: adc: stm32-adc: fix runtime autosuspend delay when slow polling
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Message ID 1579854369-7972-1-git-send-email-fabrice.gasnier@st.com
State New
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Series
  • iio: adc: stm32-adc: fix runtime autosuspend delay when slow polling
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Commit Message

Fabrice Gasnier Jan. 24, 2020, 8:26 a.m. UTC
When the ADC is runtime suspended and starting a conversion, the stm32-adc
driver calls pm_runtime_get_sync() that gets cascaded to the parent
(e.g. runtime resume of stm32-adc-core driver). This also kicks the
autosuspend delay (e.g. 2s) of the parent.
Once the ADC is active, calling pm_runtime_get_sync() again (upon a new
capture) won't kick the autosuspend delay for the parent (stm32-adc-core
driver) as already active.

Currently, this makes the stm32-adc-core driver go in suspend state
every 2s when doing slow polling. As an example, doing a capture, e.g.
cat in_voltageY_raw at a 0.2s rate, the auto suspend delay for the parent
isn't refreshed. Once it expires, the parent immediately falls into
runtime suspended state, in between two captures, as soon as the child
driver falls into runtime suspend state:
- e.g. after 2s, + child calls pm_runtime_put_autosuspend() + 100ms
  autosuspend delay of the child.
- stm32-adc-core switches off regulators, clocks and so on.
- They get switched on back again 100ms later in this example (at 2.2s).

So, add an explicit call to pm_runtime_mark_last_busy() for the parent
driver (stm32-adc-core), synchronously with the child driver (stm32-adc),
to avoid this.

Fixes: 9bdbb1139ca1 ("iio: adc: stm32-adc: add power management support")

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
 drivers/iio/adc/stm32-adc.c | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Jonathan Cameron Feb. 2, 2020, 3:33 p.m. UTC | #1
On Fri, 24 Jan 2020 09:26:09 +0100
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> When the ADC is runtime suspended and starting a conversion, the stm32-adc
> driver calls pm_runtime_get_sync() that gets cascaded to the parent
> (e.g. runtime resume of stm32-adc-core driver). This also kicks the
> autosuspend delay (e.g. 2s) of the parent.
> Once the ADC is active, calling pm_runtime_get_sync() again (upon a new
> capture) won't kick the autosuspend delay for the parent (stm32-adc-core
> driver) as already active.
> 
> Currently, this makes the stm32-adc-core driver go in suspend state
> every 2s when doing slow polling. As an example, doing a capture, e.g.
> cat in_voltageY_raw at a 0.2s rate, the auto suspend delay for the parent
> isn't refreshed. Once it expires, the parent immediately falls into
> runtime suspended state, in between two captures, as soon as the child
> driver falls into runtime suspend state:
> - e.g. after 2s, + child calls pm_runtime_put_autosuspend() + 100ms
>   autosuspend delay of the child.
> - stm32-adc-core switches off regulators, clocks and so on.
> - They get switched on back again 100ms later in this example (at 2.2s).
> 
> So, add an explicit call to pm_runtime_mark_last_busy() for the parent
> driver (stm32-adc-core), synchronously with the child driver (stm32-adc),
> to avoid this.
> 
> Fixes: 9bdbb1139ca1 ("iio: adc: stm32-adc: add power management support")
> 
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>

Hi Fabrice,

Whilst this will clearly work, it seems like a somewhat adhoc solution.
Power management specialists (cc'd):  Is this what we should be doing, or
have Fabrice and I both missed something that we should be doing here?

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stm32-adc.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index 3b291d7..670157e 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -1157,6 +1157,7 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev,
>  
>  	stm32_adc_conv_irq_disable(adc);
>  
> +	pm_runtime_mark_last_busy(dev->parent);
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
>  
> @@ -1278,6 +1279,7 @@ static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev,
>  	adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength);
>  
>  	ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask);
> +	pm_runtime_mark_last_busy(dev->parent);
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
>  
> @@ -1329,6 +1331,7 @@ static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev,
>  	else
>  		*readval = stm32_adc_readl(adc, reg);
>  
> +	pm_runtime_mark_last_busy(dev->parent);
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
>  
> @@ -1451,6 +1454,7 @@ static int __stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
>  err_clr_trig:
>  	stm32_adc_set_trig(indio_dev, NULL);
>  err_pm_put:
> +	pm_runtime_mark_last_busy(dev->parent);
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
>  
> @@ -1487,6 +1491,7 @@ static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
>  	if (stm32_adc_set_trig(indio_dev, NULL))
>  		dev_err(&indio_dev->dev, "Can't clear trigger\n");
>  
> +	pm_runtime_mark_last_busy(dev->parent);
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
>  }
> @@ -1874,6 +1879,7 @@ static int stm32_adc_probe(struct platform_device *pdev)
>  		goto err_hw_stop;
>  	}
>  
> +	pm_runtime_mark_last_busy(dev->parent);
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
>
Fabrice Gasnier Feb. 12, 2020, 2:02 p.m. UTC | #2
On 2/2/20 4:33 PM, Jonathan Cameron wrote:
> On Fri, 24 Jan 2020 09:26:09 +0100
> Fabrice Gasnier <fabrice.gasnier@st.com> wrote:
> 
>> When the ADC is runtime suspended and starting a conversion, the stm32-adc
>> driver calls pm_runtime_get_sync() that gets cascaded to the parent
>> (e.g. runtime resume of stm32-adc-core driver). This also kicks the
>> autosuspend delay (e.g. 2s) of the parent.
>> Once the ADC is active, calling pm_runtime_get_sync() again (upon a new
>> capture) won't kick the autosuspend delay for the parent (stm32-adc-core
>> driver) as already active.
>>
>> Currently, this makes the stm32-adc-core driver go in suspend state
>> every 2s when doing slow polling. As an example, doing a capture, e.g.
>> cat in_voltageY_raw at a 0.2s rate, the auto suspend delay for the parent
>> isn't refreshed. Once it expires, the parent immediately falls into
>> runtime suspended state, in between two captures, as soon as the child
>> driver falls into runtime suspend state:
>> - e.g. after 2s, + child calls pm_runtime_put_autosuspend() + 100ms
>>   autosuspend delay of the child.
>> - stm32-adc-core switches off regulators, clocks and so on.
>> - They get switched on back again 100ms later in this example (at 2.2s).
>>
>> So, add an explicit call to pm_runtime_mark_last_busy() for the parent
>> driver (stm32-adc-core), synchronously with the child driver (stm32-adc),
>> to avoid this.
>>
>> Fixes: 9bdbb1139ca1 ("iio: adc: stm32-adc: add power management support")
>>
>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> 
> Hi Fabrice,
> 
> Whilst this will clearly work, it seems like a somewhat adhoc solution.
> Power management specialists (cc'd):  Is this what we should be doing, or
> have Fabrice and I both missed something that we should be doing here?

Hi all, PM specialists,

As per my understanding, pm_runtime_mark_last_busy() doesn't cascade to
the parent device:

- in pm_runtime.h:
static inline void pm_runtime_mark_last_busy(struct device *dev)
{
	WRITE_ONCE(dev->power.last_busy, ktime_get_mono_fast_ns());
}

STM32 ADC driver uses a model with an autosupsend delay for
- a parent driver to handle common resources, registers etc.
- child drivers for each ADC.

So the question is on how to fix the behavior I described:
1: Child  activity with "short" autosuspend_delay
2: Parent activity with "longer" autosuspend_delay
     _     _     _     _     _       _     _     _
1: _| |___| |___| |___| |___| |_..._| |___| |___| |_...

    v v   v v   v v   v v   v v ... v v   v v   v v
    | |                                     |   |
    | +- pm_runtime_mark_last_busy()        |   |
    | +- pm_runtime_put_autosuspend()       v   |
    |                                       |   |
    +--- pm_runtime_get_sync()              |   v
    |                                       |   |
    +---> expires after autosuspend_delay   |   |
    |                                       |   |
    v                                       v   v
     _______________________________________     ___...
2: _|                           ...         |___|

Glitches on parent dev near autosuspend_delay ^

- does the child driver needs to "kick" parent driver with
pm_runtime_mark_last_busy(), as proposed in current patch ?

- or is it something that should be done by PM runtime core routines ?
e.g. make pm_runtime_mark_last_busy() recursive or something else ?

Please advise
Best regards,
Fabrice

> 
> Thanks,
> 
> Jonathan
> 
>> ---
>>  drivers/iio/adc/stm32-adc.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
>> index 3b291d7..670157e 100644
>> --- a/drivers/iio/adc/stm32-adc.c
>> +++ b/drivers/iio/adc/stm32-adc.c
>> @@ -1157,6 +1157,7 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev,
>>  
>>  	stm32_adc_conv_irq_disable(adc);
>>  
>> +	pm_runtime_mark_last_busy(dev->parent);
>>  	pm_runtime_mark_last_busy(dev);
>>  	pm_runtime_put_autosuspend(dev);
>>  
>> @@ -1278,6 +1279,7 @@ static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev,
>>  	adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength);
>>  
>>  	ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask);
>> +	pm_runtime_mark_last_busy(dev->parent);
>>  	pm_runtime_mark_last_busy(dev);
>>  	pm_runtime_put_autosuspend(dev);
>>  
>> @@ -1329,6 +1331,7 @@ static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev,
>>  	else
>>  		*readval = stm32_adc_readl(adc, reg);
>>  
>> +	pm_runtime_mark_last_busy(dev->parent);
>>  	pm_runtime_mark_last_busy(dev);
>>  	pm_runtime_put_autosuspend(dev);
>>  
>> @@ -1451,6 +1454,7 @@ static int __stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
>>  err_clr_trig:
>>  	stm32_adc_set_trig(indio_dev, NULL);
>>  err_pm_put:
>> +	pm_runtime_mark_last_busy(dev->parent);
>>  	pm_runtime_mark_last_busy(dev);
>>  	pm_runtime_put_autosuspend(dev);
>>  
>> @@ -1487,6 +1491,7 @@ static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
>>  	if (stm32_adc_set_trig(indio_dev, NULL))
>>  		dev_err(&indio_dev->dev, "Can't clear trigger\n");
>>  
>> +	pm_runtime_mark_last_busy(dev->parent);
>>  	pm_runtime_mark_last_busy(dev);
>>  	pm_runtime_put_autosuspend(dev);
>>  }
>> @@ -1874,6 +1879,7 @@ static int stm32_adc_probe(struct platform_device *pdev)
>>  		goto err_hw_stop;
>>  	}
>>  
>> +	pm_runtime_mark_last_busy(dev->parent);
>>  	pm_runtime_mark_last_busy(dev);
>>  	pm_runtime_put_autosuspend(dev);
>>  
>

Patch
diff mbox series

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 3b291d7..670157e 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -1157,6 +1157,7 @@  static int stm32_adc_single_conv(struct iio_dev *indio_dev,
 
 	stm32_adc_conv_irq_disable(adc);
 
+	pm_runtime_mark_last_busy(dev->parent);
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
 
@@ -1278,6 +1279,7 @@  static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev,
 	adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength);
 
 	ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask);
+	pm_runtime_mark_last_busy(dev->parent);
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
 
@@ -1329,6 +1331,7 @@  static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev,
 	else
 		*readval = stm32_adc_readl(adc, reg);
 
+	pm_runtime_mark_last_busy(dev->parent);
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
 
@@ -1451,6 +1454,7 @@  static int __stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
 err_clr_trig:
 	stm32_adc_set_trig(indio_dev, NULL);
 err_pm_put:
+	pm_runtime_mark_last_busy(dev->parent);
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
 
@@ -1487,6 +1491,7 @@  static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
 	if (stm32_adc_set_trig(indio_dev, NULL))
 		dev_err(&indio_dev->dev, "Can't clear trigger\n");
 
+	pm_runtime_mark_last_busy(dev->parent);
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
 }
@@ -1874,6 +1879,7 @@  static int stm32_adc_probe(struct platform_device *pdev)
 		goto err_hw_stop;
 	}
 
+	pm_runtime_mark_last_busy(dev->parent);
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);