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[PATCH V2 2/3] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances

Sibi Sankar posted 3 patches 1 year, 6 months ago
There is a newer version of this series
[PATCH V2 2/3] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances
Posted by Sibi Sankar 1 year, 6 months ago 
The multiple BWMONv4 instances available on the X1E80100 SoC use the
same interrupt number. Mark them are shared to allow for re-use across
instances. Handle the ensuing race introduced by relying on bwmon_disable
to disable the interrupt and coupled with explicit request/free irqs.

Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
---

v2:
* Use explicit request/free irq and add comments regarding the race
  introduced when adding the IRQF_SHARED flag. [Krzysztof/Dmitry]

 drivers/soc/qcom/icc-bwmon.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
index fb323b3364db..4a4e28b41509 100644
--- a/drivers/soc/qcom/icc-bwmon.c
+++ b/drivers/soc/qcom/icc-bwmon.c
@@ -781,9 +781,10 @@ static int bwmon_probe(struct platform_device *pdev)
 	bwmon->dev = dev;
 
 	bwmon_disable(bwmon);
-	ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
-					bwmon_intr_thread,
-					IRQF_ONESHOT, dev_name(dev), bwmon);
+
+	/* SoCs with multiple cpu-bwmon instances can end up using a shared interrupt line */
+	ret = request_threaded_irq(bwmon->irq, bwmon_intr, bwmon_intr_thread,
+				   IRQF_ONESHOT | IRQF_SHARED, dev_name(dev), bwmon);
 	if (ret)
 		return dev_err_probe(dev, ret, "failed to request IRQ\n");
 
@@ -798,6 +799,13 @@ static void bwmon_remove(struct platform_device *pdev)
 	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
 
 	bwmon_disable(bwmon);
+
+	/*
+	 * Handle the race introduced, when dealing with multiple bwmon instances
+	 * using a shared interrupt line, by relying on bwmon_disable to disable
+	 * the interrupt and followed by an explicit free.
+	 */
+	free_irq(bwmon->irq, bwmon);
 }
 
 static const struct icc_bwmon_data msm8998_bwmon_data = {
-- 
2.34.1
Re: [PATCH V2 2/3] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances
Posted by Bjorn Andersson 1 year, 5 months ago 
On Tue, Jun 18, 2024 at 09:13:05PM GMT, Sibi Sankar wrote:
> The multiple BWMONv4 instances available on the X1E80100 SoC use the
> same interrupt number. Mark them are shared to allow for re-use across
> instances. Handle the ensuing race introduced by relying on bwmon_disable

In an effort to educate the reader, could you please describe what the
race condition is here.

It would also make sense to break this ("Handle...") into a separate
paragraph.

Regards,
Bjorn

> to disable the interrupt and coupled with explicit request/free irqs.
> 
> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
> ---
> 
> v2:
> * Use explicit request/free irq and add comments regarding the race
>   introduced when adding the IRQF_SHARED flag. [Krzysztof/Dmitry]
> 
>  drivers/soc/qcom/icc-bwmon.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
> index fb323b3364db..4a4e28b41509 100644
> --- a/drivers/soc/qcom/icc-bwmon.c
> +++ b/drivers/soc/qcom/icc-bwmon.c
> @@ -781,9 +781,10 @@ static int bwmon_probe(struct platform_device *pdev)
>  	bwmon->dev = dev;
>  
>  	bwmon_disable(bwmon);
> -	ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
> -					bwmon_intr_thread,
> -					IRQF_ONESHOT, dev_name(dev), bwmon);
> +
> +	/* SoCs with multiple cpu-bwmon instances can end up using a shared interrupt line */
> +	ret = request_threaded_irq(bwmon->irq, bwmon_intr, bwmon_intr_thread,
> +				   IRQF_ONESHOT | IRQF_SHARED, dev_name(dev), bwmon);
>  	if (ret)
>  		return dev_err_probe(dev, ret, "failed to request IRQ\n");
>  
> @@ -798,6 +799,13 @@ static void bwmon_remove(struct platform_device *pdev)
>  	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
>  
>  	bwmon_disable(bwmon);
> +
> +	/*
> +	 * Handle the race introduced, when dealing with multiple bwmon instances
> +	 * using a shared interrupt line, by relying on bwmon_disable to disable
> +	 * the interrupt and followed by an explicit free.
> +	 */
> +	free_irq(bwmon->irq, bwmon);
>  }
>  
>  static const struct icc_bwmon_data msm8998_bwmon_data = {
> -- 
> 2.34.1
>
Re: [PATCH V2 2/3] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances
Posted by Sibi Sankar 1 year, 5 months ago 

On 6/21/24 11:15, Bjorn Andersson wrote:
> On Tue, Jun 18, 2024 at 09:13:05PM GMT, Sibi Sankar wrote:
>> The multiple BWMONv4 instances available on the X1E80100 SoC use the
>> same interrupt number. Mark them are shared to allow for re-use across
>> instances. Handle the ensuing race introduced by relying on bwmon_disable
> 
> In an effort to educate the reader, could you please describe what the
> race condition is here.
> 
> It would also make sense to break this ("Handle...") into a separate
> paragraph.

Ack, will make the changes in the next re-spin.

-Sibi

> 
> Regards,
> Bjorn
> 
>> to disable the interrupt and coupled with explicit request/free irqs.
>>
>> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
>> ---
>>
>> v2:
>> * Use explicit request/free irq and add comments regarding the race
>>    introduced when adding the IRQF_SHARED flag. [Krzysztof/Dmitry]
>>
>>   drivers/soc/qcom/icc-bwmon.c | 14 +++++++++++---
>>   1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
>> index fb323b3364db..4a4e28b41509 100644
>> --- a/drivers/soc/qcom/icc-bwmon.c
>> +++ b/drivers/soc/qcom/icc-bwmon.c
>> @@ -781,9 +781,10 @@ static int bwmon_probe(struct platform_device *pdev)
>>   	bwmon->dev = dev;
>>   
>>   	bwmon_disable(bwmon);
>> -	ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
>> -					bwmon_intr_thread,
>> -					IRQF_ONESHOT, dev_name(dev), bwmon);
>> +
>> +	/* SoCs with multiple cpu-bwmon instances can end up using a shared interrupt line */
>> +	ret = request_threaded_irq(bwmon->irq, bwmon_intr, bwmon_intr_thread,
>> +				   IRQF_ONESHOT | IRQF_SHARED, dev_name(dev), bwmon);
>>   	if (ret)
>>   		return dev_err_probe(dev, ret, "failed to request IRQ\n");
>>   
>> @@ -798,6 +799,13 @@ static void bwmon_remove(struct platform_device *pdev)
>>   	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
>>   
>>   	bwmon_disable(bwmon);
>> +
>> +	/*
>> +	 * Handle the race introduced, when dealing with multiple bwmon instances
>> +	 * using a shared interrupt line, by relying on bwmon_disable to disable
>> +	 * the interrupt and followed by an explicit free.
>> +	 */
>> +	free_irq(bwmon->irq, bwmon);
>>   }
>>   
>>   static const struct icc_bwmon_data msm8998_bwmon_data = {
>> -- 
>> 2.34.1
>>
Re: [PATCH V2 2/3] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances
Posted by Dmitry Baryshkov 1 year, 6 months ago 
On Tue, Jun 18, 2024 at 09:13:05PM GMT, Sibi Sankar wrote:
> The multiple BWMONv4 instances available on the X1E80100 SoC use the
> same interrupt number. Mark them are shared to allow for re-use across
> instances. Handle the ensuing race introduced by relying on bwmon_disable
> to disable the interrupt and coupled with explicit request/free irqs.
> 
> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
> ---
> 
> v2:
> * Use explicit request/free irq and add comments regarding the race
>   introduced when adding the IRQF_SHARED flag. [Krzysztof/Dmitry]
> 
>  drivers/soc/qcom/icc-bwmon.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
> index fb323b3364db..4a4e28b41509 100644
> --- a/drivers/soc/qcom/icc-bwmon.c
> +++ b/drivers/soc/qcom/icc-bwmon.c
> @@ -781,9 +781,10 @@ static int bwmon_probe(struct platform_device *pdev)
>  	bwmon->dev = dev;
>  
>  	bwmon_disable(bwmon);
> -	ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
> -					bwmon_intr_thread,
> -					IRQF_ONESHOT, dev_name(dev), bwmon);
> +
> +	/* SoCs with multiple cpu-bwmon instances can end up using a shared interrupt line */

... using devm_ here might result in the IRQ handler being executed
after bwmon_disable in bwmon_remove()

> +	ret = request_threaded_irq(bwmon->irq, bwmon_intr, bwmon_intr_thread,
> +				   IRQF_ONESHOT | IRQF_SHARED, dev_name(dev), bwmon);
>  	if (ret)
>  		return dev_err_probe(dev, ret, "failed to request IRQ\n");
>  
> @@ -798,6 +799,13 @@ static void bwmon_remove(struct platform_device *pdev)
>  	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
>  
>  	bwmon_disable(bwmon);
> +
> +	/*
> +	 * Handle the race introduced, when dealing with multiple bwmon instances
> +	 * using a shared interrupt line, by relying on bwmon_disable to disable
> +	 * the interrupt and followed by an explicit free.
> +	 */

This sounds more like a part of the commit message. The comment before
request_threaded_irq() should be enough.

> +	free_irq(bwmon->irq, bwmon);
>  }
>  
>  static const struct icc_bwmon_data msm8998_bwmon_data = {
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry
Re: [PATCH V2 2/3] soc: qcom: icc-bwmon: Allow for interrupts to be shared across instances
Posted by Sibi Sankar 1 year, 5 months ago 

On 6/19/24 00:25, Dmitry Baryshkov wrote:
> On Tue, Jun 18, 2024 at 09:13:05PM GMT, Sibi Sankar wrote:
>> The multiple BWMONv4 instances available on the X1E80100 SoC use the
>> same interrupt number. Mark them are shared to allow for re-use across
>> instances. Handle the ensuing race introduced by relying on bwmon_disable
>> to disable the interrupt and coupled with explicit request/free irqs.
>>
>> Signed-off-by: Sibi Sankar <quic_sibis@quicinc.com>
>> ---
>>
>> v2:
>> * Use explicit request/free irq and add comments regarding the race
>>    introduced when adding the IRQF_SHARED flag. [Krzysztof/Dmitry]
>>
>>   drivers/soc/qcom/icc-bwmon.c | 14 +++++++++++---
>>   1 file changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/soc/qcom/icc-bwmon.c b/drivers/soc/qcom/icc-bwmon.c
>> index fb323b3364db..4a4e28b41509 100644
>> --- a/drivers/soc/qcom/icc-bwmon.c
>> +++ b/drivers/soc/qcom/icc-bwmon.c
>> @@ -781,9 +781,10 @@ static int bwmon_probe(struct platform_device *pdev)
>>   	bwmon->dev = dev;
>>   
>>   	bwmon_disable(bwmon);
>> -	ret = devm_request_threaded_irq(dev, bwmon->irq, bwmon_intr,
>> -					bwmon_intr_thread,
>> -					IRQF_ONESHOT, dev_name(dev), bwmon);
>> +
>> +	/* SoCs with multiple cpu-bwmon instances can end up using a shared interrupt line */
> 
> ... using devm_ here might result in the IRQ handler being executed
> after bwmon_disable in bwmon_remove()

Ack

> 
>> +	ret = request_threaded_irq(bwmon->irq, bwmon_intr, bwmon_intr_thread,
>> +				   IRQF_ONESHOT | IRQF_SHARED, dev_name(dev), bwmon);
>>   	if (ret)
>>   		return dev_err_probe(dev, ret, "failed to request IRQ\n");
>>   
>> @@ -798,6 +799,13 @@ static void bwmon_remove(struct platform_device *pdev)
>>   	struct icc_bwmon *bwmon = platform_get_drvdata(pdev);
>>   
>>   	bwmon_disable(bwmon);
>> +
>> +	/*
>> +	 * Handle the race introduced, when dealing with multiple bwmon instances
>> +	 * using a shared interrupt line, by relying on bwmon_disable to disable
>> +	 * the interrupt and followed by an explicit free.
>> +	 */
> 
> This sounds more like a part of the commit message. The comment before
> request_threaded_irq() should be enough.

Ack

-Sibi

> 
>> +	free_irq(bwmon->irq, bwmon);
>>   }
>>   
>>   static const struct icc_bwmon_data msm8998_bwmon_data = {
>> -- 
>> 2.34.1
>>
>

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