[PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[Heiner Kallweit]

The patch fixes / extends the runtime PM handling.
- Currently the driver instructs the SPI core to use auto-suspend
  but doesn't configure it. Add the necessary calls and let it
  autosuspend after probe.
- In case the driver registration fails runtime PM needs to be
  properly disabled.

Signed-off-by: Heiner Kallweit <hkallweit1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 drivers/spi/spi-s3c64xx.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index c4d3b06..15a6de1 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -32,6 +32,7 @@
 #define MAX_SPI_PORTS		6
 #define S3C64XX_SPI_QUIRK_POLL		(1 << 0)
 #define S3C64XX_SPI_QUIRK_CS_AUTO	(1 << 1)
+#define AUTOSUSPEND_TIMEOUT     2000
 
 /* Registers and bit-fields */
 
@@ -1180,13 +1181,15 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
 	       S3C64XX_SPI_INT_TX_OVERRUN_EN | S3C64XX_SPI_INT_TX_UNDERRUN_EN,
 	       sdd->regs + S3C64XX_SPI_INT_EN);
 
+	pm_runtime_set_autosuspend_delay(dev, AUTOSUSPEND_TIMEOUT);
+	pm_runtime_use_autosuspend(dev);
 	pm_runtime_set_active(dev);
 	pm_runtime_enable(dev);
 
 	ret = devm_spi_register_master(dev, master);
 	if (ret != 0) {
 		dev_err(dev, "cannot register SPI master: %d\n", ret);
-		goto err3;
+		goto err4;
 	}
 
 	dev_dbg(dev, "Samsung SoC SPI Driver loaded for Bus SPI-%d with %d Slaves attached\n",
@@ -1195,8 +1198,14 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
 					mem_res, (FIFO_LVL_MASK(sdd) >> 1) + 1,
 					sdd->rx_dma.dmach, sdd->tx_dma.dmach);
 
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_autosuspend(dev);
+
 	return 0;
 
+err4:
+	pm_runtime_disable(dev);
+	pm_runtime_set_suspended(dev);
 err3:
 	clk_disable_unprepare(sdd->src_clk);
 err2:
-- 
2.5.0

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Re: [PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[Krzysztof Kozlowski]

On 19.08.2015 06:06, Heiner Kallweit wrote:
> The patch fixes / extends the runtime PM handling.
> - Currently the driver instructs the SPI core to use auto-suspend
>   but doesn't configure it. Add the necessary calls and let it
>   autosuspend after probe.

After quick look at the driver I think it does not use autosuspend
fully. It just sets master->auto_runtime_pm (so the core code will use
autosuspend) but its own calls to pm_runtime_put() are regular ones.
Shouldn't this be enhanced as well?

> - In case the driver registration fails runtime PM needs to be
>   properly disabled.
> 
> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
> ---
>  drivers/spi/spi-s3c64xx.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
> index c4d3b06..15a6de1 100644
> --- a/drivers/spi/spi-s3c64xx.c
> +++ b/drivers/spi/spi-s3c64xx.c
> @@ -32,6 +32,7 @@
>  #define MAX_SPI_PORTS		6
>  #define S3C64XX_SPI_QUIRK_POLL		(1 << 0)
>  #define S3C64XX_SPI_QUIRK_CS_AUTO	(1 << 1)
> +#define AUTOSUSPEND_TIMEOUT     2000
>  
>  /* Registers and bit-fields */
>  
> @@ -1180,13 +1181,15 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>  	       S3C64XX_SPI_INT_TX_OVERRUN_EN | S3C64XX_SPI_INT_TX_UNDERRUN_EN,
>  	       sdd->regs + S3C64XX_SPI_INT_EN);
>  
> +	pm_runtime_set_autosuspend_delay(dev, AUTOSUSPEND_TIMEOUT);
> +	pm_runtime_use_autosuspend(dev);
>  	pm_runtime_set_active(dev);
>  	pm_runtime_enable(dev);
>  
>  	ret = devm_spi_register_master(dev, master);
>  	if (ret != 0) {
>  		dev_err(dev, "cannot register SPI master: %d\n", ret);
> -		goto err3;
> +		goto err4;
>  	}
>  
>  	dev_dbg(dev, "Samsung SoC SPI Driver loaded for Bus SPI-%d with %d Slaves attached\n",
> @@ -1195,8 +1198,14 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>  					mem_res, (FIFO_LVL_MASK(sdd) >> 1) + 1,
>  					sdd->rx_dma.dmach, sdd->tx_dma.dmach);
>  
> +	pm_runtime_mark_last_busy(dev);
> +	pm_runtime_autosuspend(dev);

There is a high chance that device will be suspended already at this
point because pm_runtime_put() in setup. In most cases (when SPI is
started) this won't do anything so we are back at first of my questions
- shouldn't you update pm_runtime_put() calls?

Additionally (which is not related to your patch) shouldn't we
pm_runtime_get() at some point in probe() to be sure that it won't be
suspended to early?

> +
>  	return 0;
>  
> +err4:
> +	pm_runtime_disable(dev);
> +	pm_runtime_set_suspended(dev);

Please separate fixes from enhancements into different patches.

Best regards,
Krzysztof

>  err3:
>  	clk_disable_unprepare(sdd->src_clk);
>  err2:
> 

Re: [PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[Heiner Kallweit]

Am 19.08.2015 um 02:35 schrieb Krzysztof Kozlowski:
> On 19.08.2015 06:06, Heiner Kallweit wrote:
>> The patch fixes / extends the runtime PM handling.
>> - Currently the driver instructs the SPI core to use auto-suspend
>>   but doesn't configure it. Add the necessary calls and let it
>>   autosuspend after probe.
> 
> After quick look at the driver I think it does not use autosuspend
> fully. It just sets master->auto_runtime_pm (so the core code will use
> autosuspend) but its own calls to pm_runtime_put() are regular ones.
> Shouldn't this be enhanced as well?
Right, the pm_runtime_put calls in s3c64xx_spi_setup should be
replaced as well. Will provide an updated patch.
> 
>> - In case the driver registration fails runtime PM needs to be
>>   properly disabled.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>> ---
>>  drivers/spi/spi-s3c64xx.c | 11 ++++++++++-
>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> index c4d3b06..15a6de1 100644
>> --- a/drivers/spi/spi-s3c64xx.c
>> +++ b/drivers/spi/spi-s3c64xx.c
>> @@ -32,6 +32,7 @@
>>  #define MAX_SPI_PORTS		6
>>  #define S3C64XX_SPI_QUIRK_POLL		(1 << 0)
>>  #define S3C64XX_SPI_QUIRK_CS_AUTO	(1 << 1)
>> +#define AUTOSUSPEND_TIMEOUT     2000
>>  
>>  /* Registers and bit-fields */
>>  
>> @@ -1180,13 +1181,15 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>  	       S3C64XX_SPI_INT_TX_OVERRUN_EN | S3C64XX_SPI_INT_TX_UNDERRUN_EN,
>>  	       sdd->regs + S3C64XX_SPI_INT_EN);
>>  
>> +	pm_runtime_set_autosuspend_delay(dev, AUTOSUSPEND_TIMEOUT);
>> +	pm_runtime_use_autosuspend(dev);
>>  	pm_runtime_set_active(dev);
>>  	pm_runtime_enable(dev);
>>  
>>  	ret = devm_spi_register_master(dev, master);
>>  	if (ret != 0) {
>>  		dev_err(dev, "cannot register SPI master: %d\n", ret);
>> -		goto err3;
>> +		goto err4;
>>  	}
>>  
>>  	dev_dbg(dev, "Samsung SoC SPI Driver loaded for Bus SPI-%d with %d Slaves attached\n",
>> @@ -1195,8 +1198,14 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>  					mem_res, (FIFO_LVL_MASK(sdd) >> 1) + 1,
>>  					sdd->rx_dma.dmach, sdd->tx_dma.dmach);
>>  
>> +	pm_runtime_mark_last_busy(dev);
>> +	pm_runtime_autosuspend(dev);
> 
> There is a high chance that device will be suspended already at this
> point because pm_runtime_put() in setup. In most cases (when SPI is
> started) this won't do anything so we are back at first of my questions
> - shouldn't you update pm_runtime_put() calls?
Yes, these calls should be updated.
> 
> Additionally (which is not related to your patch) shouldn't we
> pm_runtime_get() at some point in probe() to be sure that it won't be
> suspended to early?
Not 100% sure at this moment, I will check.
> 
>> +
>>  	return 0;
>>  
>> +err4:
>> +	pm_runtime_disable(dev);
>> +	pm_runtime_set_suspended(dev);
> 
> Please separate fixes from enhancements into different patches.
OK, will do so.
> 
> Best regards,
> Krzysztof
> 
>>  err3:
>>  	clk_disable_unprepare(sdd->src_clk);
>>  err2:
>>
> 
> 

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Re: [PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[Heiner Kallweit]

Am 19.08.2015 um 07:54 schrieb Heiner Kallweit:
> Am 19.08.2015 um 02:35 schrieb Krzysztof Kozlowski:
>> On 19.08.2015 06:06, Heiner Kallweit wrote:
>>> The patch fixes / extends the runtime PM handling.
>>> - Currently the driver instructs the SPI core to use auto-suspend
>>>   but doesn't configure it. Add the necessary calls and let it
>>>   autosuspend after probe.
>>
>> After quick look at the driver I think it does not use autosuspend
>> fully. It just sets master->auto_runtime_pm (so the core code will use
>> autosuspend) but its own calls to pm_runtime_put() are regular ones.
>> Shouldn't this be enhanced as well?
> Right, the pm_runtime_put calls in s3c64xx_spi_setup should be
> replaced as well. Will provide an updated patch.
>>
>>> - In case the driver registration fails runtime PM needs to be
>>>   properly disabled.
>>>
>>> Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
>>> ---
>>>  drivers/spi/spi-s3c64xx.c | 11 ++++++++++-
>>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>> index c4d3b06..15a6de1 100644
>>> --- a/drivers/spi/spi-s3c64xx.c
>>> +++ b/drivers/spi/spi-s3c64xx.c
>>> @@ -32,6 +32,7 @@
>>>  #define MAX_SPI_PORTS		6
>>>  #define S3C64XX_SPI_QUIRK_POLL		(1 << 0)
>>>  #define S3C64XX_SPI_QUIRK_CS_AUTO	(1 << 1)
>>> +#define AUTOSUSPEND_TIMEOUT     2000
>>>  
>>>  /* Registers and bit-fields */
>>>  
>>> @@ -1180,13 +1181,15 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>>  	       S3C64XX_SPI_INT_TX_OVERRUN_EN | S3C64XX_SPI_INT_TX_UNDERRUN_EN,
>>>  	       sdd->regs + S3C64XX_SPI_INT_EN);
>>>  
>>> +	pm_runtime_set_autosuspend_delay(dev, AUTOSUSPEND_TIMEOUT);
>>> +	pm_runtime_use_autosuspend(dev);
>>>  	pm_runtime_set_active(dev);
>>>  	pm_runtime_enable(dev);
>>>  
>>>  	ret = devm_spi_register_master(dev, master);
>>>  	if (ret != 0) {
>>>  		dev_err(dev, "cannot register SPI master: %d\n", ret);
>>> -		goto err3;
>>> +		goto err4;
>>>  	}
>>>  
>>>  	dev_dbg(dev, "Samsung SoC SPI Driver loaded for Bus SPI-%d with %d Slaves attached\n",
>>> @@ -1195,8 +1198,14 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>>  					mem_res, (FIFO_LVL_MASK(sdd) >> 1) + 1,
>>>  					sdd->rx_dma.dmach, sdd->tx_dma.dmach);
>>>  
>>> +	pm_runtime_mark_last_busy(dev);
>>> +	pm_runtime_autosuspend(dev);
>>
>> There is a high chance that device will be suspended already at this
>> point because pm_runtime_put() in setup. In most cases (when SPI is
>> started) this won't do anything so we are back at first of my questions
>> - shouldn't you update pm_runtime_put() calls?
> Yes, these calls should be updated.
>>
>> Additionally (which is not related to your patch) shouldn't we
>> pm_runtime_get() at some point in probe() to be sure that it won't be
>> suspended to early?
> Not 100% sure at this moment, I will check.
Kernel documentation says:
"Note, if the device may execute pm_runtime calls during the probe (such as
if it is registers with a subsystem that may call back in) then the
pm_runtime_get_sync() call paired with a pm_runtime_put() call will be
appropriate to ensure that the device is not put back to sleep during the
probe. This can happen with systems such as the network device layer."

I don't think this applies to SPI but I'm not expert enough to guarantee.
At least no other SPI driver using runtime PM protects the probe function this way.
Therefore I would dare to leave it as it is, especially as there don't seem
to be any related known problems with SPI drivers.

Regards, Heiner
>>
>>> +
>>>  	return 0;
>>>  
>>> +err4:
>>> +	pm_runtime_disable(dev);
>>> +	pm_runtime_set_suspended(dev);
>>
>> Please separate fixes from enhancements into different patches.
> OK, will do so.
>>
>> Best regards,
>> Krzysztof
>>
>>>  err3:
>>>  	clk_disable_unprepare(sdd->src_clk);
>>>  err2:
>>>
>>
>>
> 

Re: [PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[Krzysztof Kozlowski]

On 20.08.2015 04:36, Heiner Kallweit wrote:
> Am 19.08.2015 um 07:54 schrieb Heiner Kallweit:
>> Am 19.08.2015 um 02:35 schrieb Krzysztof Kozlowski:
>>> On 19.08.2015 06:06, Heiner Kallweit wrote:
>>>> The patch fixes / extends the runtime PM handling.
>>>> - Currently the driver instructs the SPI core to use auto-suspend
>>>>   but doesn't configure it. Add the necessary calls and let it
>>>>   autosuspend after probe.
>>>
>>> After quick look at the driver I think it does not use autosuspend
>>> fully. It just sets master->auto_runtime_pm (so the core code will use
>>> autosuspend) but its own calls to pm_runtime_put() are regular ones.
>>> Shouldn't this be enhanced as well?
>> Right, the pm_runtime_put calls in s3c64xx_spi_setup should be
>> replaced as well. Will provide an updated patch.
>>>
>>>> - In case the driver registration fails runtime PM needs to be
>>>>   properly disabled.
>>>>
>>>> Signed-off-by: Heiner Kallweit <hkallweit1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>>> ---
>>>>  drivers/spi/spi-s3c64xx.c | 11 ++++++++++-
>>>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>>> index c4d3b06..15a6de1 100644
>>>> --- a/drivers/spi/spi-s3c64xx.c
>>>> +++ b/drivers/spi/spi-s3c64xx.c
>>>> @@ -32,6 +32,7 @@
>>>>  #define MAX_SPI_PORTS		6
>>>>  #define S3C64XX_SPI_QUIRK_POLL		(1 << 0)
>>>>  #define S3C64XX_SPI_QUIRK_CS_AUTO	(1 << 1)
>>>> +#define AUTOSUSPEND_TIMEOUT     2000
>>>>  
>>>>  /* Registers and bit-fields */
>>>>  
>>>> @@ -1180,13 +1181,15 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>>>  	       S3C64XX_SPI_INT_TX_OVERRUN_EN | S3C64XX_SPI_INT_TX_UNDERRUN_EN,
>>>>  	       sdd->regs + S3C64XX_SPI_INT_EN);
>>>>  
>>>> +	pm_runtime_set_autosuspend_delay(dev, AUTOSUSPEND_TIMEOUT);
>>>> +	pm_runtime_use_autosuspend(dev);
>>>>  	pm_runtime_set_active(dev);
>>>>  	pm_runtime_enable(dev);
>>>>  
>>>>  	ret = devm_spi_register_master(dev, master);
>>>>  	if (ret != 0) {
>>>>  		dev_err(dev, "cannot register SPI master: %d\n", ret);
>>>> -		goto err3;
>>>> +		goto err4;
>>>>  	}
>>>>  
>>>>  	dev_dbg(dev, "Samsung SoC SPI Driver loaded for Bus SPI-%d with %d Slaves attached\n",
>>>> @@ -1195,8 +1198,14 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>>>  					mem_res, (FIFO_LVL_MASK(sdd) >> 1) + 1,
>>>>  					sdd->rx_dma.dmach, sdd->tx_dma.dmach);
>>>>  
>>>> +	pm_runtime_mark_last_busy(dev);
>>>> +	pm_runtime_autosuspend(dev);
>>>
>>> There is a high chance that device will be suspended already at this
>>> point because pm_runtime_put() in setup. In most cases (when SPI is
>>> started) this won't do anything so we are back at first of my questions
>>> - shouldn't you update pm_runtime_put() calls?
>> Yes, these calls should be updated.
>>>
>>> Additionally (which is not related to your patch) shouldn't we
>>> pm_runtime_get() at some point in probe() to be sure that it won't be
>>> suspended to early?
>> Not 100% sure at this moment, I will check.
> Kernel documentation says:
> "Note, if the device may execute pm_runtime calls during the probe (such as
> if it is registers with a subsystem that may call back in) then the
> pm_runtime_get_sync() call paired with a pm_runtime_put() call will be
> appropriate to ensure that the device is not put back to sleep during the
> probe. This can happen with systems such as the network device layer."
> 
> I don't think this applies to SPI but I'm not expert enough to guarantee.
> At least no other SPI driver using runtime PM protects the probe function this way.
> Therefore I would dare to leave it as it is, especially as there don't seem
> to be any related known problems with SPI drivers.

But you know that these runtime callbacks will be executed anyway during
probe because what I mentioned earlier - setup calls get and put.
Additionally pm_runtime_enable() is called in the middle of probe, not
at the end. This means that already it is assumed probe in certain time
can handle runtime callbacks.

I think it is good opportunity to fix any remaining issues with runtime
PM in this driver.

Best regards,
Krzysztof

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Re: [PATCH 2/3] spi: s3c64xx: fix runtime PM handling

[Heiner Kallweit]

Am 20.08.2015 um 01:41 schrieb Krzysztof Kozlowski:
> On 20.08.2015 04:36, Heiner Kallweit wrote:
>> Am 19.08.2015 um 07:54 schrieb Heiner Kallweit:
>>> Am 19.08.2015 um 02:35 schrieb Krzysztof Kozlowski:
>>>> On 19.08.2015 06:06, Heiner Kallweit wrote:
>>>>> The patch fixes / extends the runtime PM handling.
>>>>> - Currently the driver instructs the SPI core to use auto-suspend
>>>>>   but doesn't configure it. Add the necessary calls and let it
>>>>>   autosuspend after probe.
>>>>
>>>> After quick look at the driver I think it does not use autosuspend
>>>> fully. It just sets master->auto_runtime_pm (so the core code will use
>>>> autosuspend) but its own calls to pm_runtime_put() are regular ones.
>>>> Shouldn't this be enhanced as well?
>>> Right, the pm_runtime_put calls in s3c64xx_spi_setup should be
>>> replaced as well. Will provide an updated patch.
>>>>
>>>>> - In case the driver registration fails runtime PM needs to be
>>>>>   properly disabled.
>>>>>
>>>>> Signed-off-by: Heiner Kallweit <hkallweit1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
>>>>> ---
>>>>>  drivers/spi/spi-s3c64xx.c | 11 ++++++++++-
>>>>>  1 file changed, 10 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>>>>> index c4d3b06..15a6de1 100644
>>>>> --- a/drivers/spi/spi-s3c64xx.c
>>>>> +++ b/drivers/spi/spi-s3c64xx.c
>>>>> @@ -32,6 +32,7 @@
>>>>>  #define MAX_SPI_PORTS		6
>>>>>  #define S3C64XX_SPI_QUIRK_POLL		(1 << 0)
>>>>>  #define S3C64XX_SPI_QUIRK_CS_AUTO	(1 << 1)
>>>>> +#define AUTOSUSPEND_TIMEOUT     2000
>>>>>  
>>>>>  /* Registers and bit-fields */
>>>>>  
>>>>> @@ -1180,13 +1181,15 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>>>>  	       S3C64XX_SPI_INT_TX_OVERRUN_EN | S3C64XX_SPI_INT_TX_UNDERRUN_EN,
>>>>>  	       sdd->regs + S3C64XX_SPI_INT_EN);
>>>>>  
>>>>> +	pm_runtime_set_autosuspend_delay(dev, AUTOSUSPEND_TIMEOUT);
>>>>> +	pm_runtime_use_autosuspend(dev);
>>>>>  	pm_runtime_set_active(dev);
>>>>>  	pm_runtime_enable(dev);
>>>>>  
>>>>>  	ret = devm_spi_register_master(dev, master);
>>>>>  	if (ret != 0) {
>>>>>  		dev_err(dev, "cannot register SPI master: %d\n", ret);
>>>>> -		goto err3;
>>>>> +		goto err4;
>>>>>  	}
>>>>>  
>>>>>  	dev_dbg(dev, "Samsung SoC SPI Driver loaded for Bus SPI-%d with %d Slaves attached\n",
>>>>> @@ -1195,8 +1198,14 @@ static int s3c64xx_spi_probe(struct platform_device *pdev)
>>>>>  					mem_res, (FIFO_LVL_MASK(sdd) >> 1) + 1,
>>>>>  					sdd->rx_dma.dmach, sdd->tx_dma.dmach);
>>>>>  
>>>>> +	pm_runtime_mark_last_busy(dev);
>>>>> +	pm_runtime_autosuspend(dev);
>>>>
>>>> There is a high chance that device will be suspended already at this
>>>> point because pm_runtime_put() in setup. In most cases (when SPI is
>>>> started) this won't do anything so we are back at first of my questions
>>>> - shouldn't you update pm_runtime_put() calls?
>>> Yes, these calls should be updated.
>>>>
>>>> Additionally (which is not related to your patch) shouldn't we
>>>> pm_runtime_get() at some point in probe() to be sure that it won't be
>>>> suspended to early?
>>> Not 100% sure at this moment, I will check.
>> Kernel documentation says:
>> "Note, if the device may execute pm_runtime calls during the probe (such as
>> if it is registers with a subsystem that may call back in) then the
>> pm_runtime_get_sync() call paired with a pm_runtime_put() call will be
>> appropriate to ensure that the device is not put back to sleep during the
>> probe. This can happen with systems such as the network device layer."
>>
>> I don't think this applies to SPI but I'm not expert enough to guarantee.
>> At least no other SPI driver using runtime PM protects the probe function this way.
>> Therefore I would dare to leave it as it is, especially as there don't seem
>> to be any related known problems with SPI drivers.
> 
> But you know that these runtime callbacks will be executed anyway during
> probe because what I mentioned earlier - setup calls get and put.
> Additionally pm_runtime_enable() is called in the middle of probe, not
> at the end. This means that already it is assumed probe in certain time
> can handle runtime callbacks.
> 
> I think it is good opportunity to fix any remaining issues with runtime
> PM in this driver.
> 
> Best regards,
> Krzysztof
OK. Will include this and resend. Thanks for the review.

Regards, Heiner

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