In commit 6746eae4bbad ("coresight: cti: Fix hang in cti_disable_hw()")
PM runtime calls are removed from cti_enable_hw/cti_disable_hw. When
enabling CTI by writing enable sysfs node, clock for accessing CTI
register won't be enabled. Device will crash due to register access
issue. Add PM runtime call in enable_store to fix this issue.

Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
---
 drivers/hwtracing/coresight/coresight-cti-sysfs.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
index 6d59c815ecf5..b1ed424ae043 100644
--- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
@@ -108,10 +108,17 @@ static ssize_t enable_store(struct device *dev,
 	if (ret)
 		return ret;
 
-	if (val)
+	if (val) {
+		ret = pm_runtime_resume_and_get(dev->parent);
+		if (ret)
+			return ret;
 		ret = cti_enable(drvdata->csdev);
-	else
+		if (ret)
+			pm_runtime_put(dev->parent);
+	} else {
 		ret = cti_disable(drvdata->csdev);
+		pm_runtime_put(dev->parent);
+	}
 	if (ret)
 		return ret;
 	return size;
-- 
2.17.1

On 24/12/2022 14:17, Mao Jinlong wrote:
> In commit 6746eae4bbad ("coresight: cti: Fix hang in cti_disable_hw()")
> PM runtime calls are removed from cti_enable_hw/cti_disable_hw. When
> enabling CTI by writing enable sysfs node, clock for accessing CTI
> register won't be enabled. Device will crash due to register access
> issue. Add PM runtime call in enable_store to fix this issue.
> 
> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
> ---
>  drivers/hwtracing/coresight/coresight-cti-sysfs.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
> index 6d59c815ecf5..b1ed424ae043 100644
> --- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
> +++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
> @@ -108,10 +108,17 @@ static ssize_t enable_store(struct device *dev,
>  	if (ret)
>  		return ret;
>  
> -	if (val)
> +	if (val) {
> +		ret = pm_runtime_resume_and_get(dev->parent);
> +		if (ret)
> +			return ret;
>  		ret = cti_enable(drvdata->csdev);
> -	else
> +		if (ret)
> +			pm_runtime_put(dev->parent);
> +	} else {
>  		ret = cti_disable(drvdata->csdev);
> +		pm_runtime_put(dev->parent);

Hi Jinlong,

This new pm_runtime_put() causes this when writing 0 to enable:

  [  483.253814] coresight-cti 23020000.cti: Runtime PM usage count
underflow!

Maybe we can modify cti_disable_hw() to return a value to indicate that
the disable actually happened, and only then call pm_runtime_put().

I suppose you could also check in the store function if it was already
enabled first, but then I don't know what kind of locking that would
need? cti_disable_hw() already seems to have a couple of locks, so maybe
the return value solution is easiest.

Thanks
James

On 04/01/2023 13:11, James Clark wrote:
> 
> 
> On 24/12/2022 14:17, Mao Jinlong wrote:
>> In commit 6746eae4bbad ("coresight: cti: Fix hang in cti_disable_hw()")
>> PM runtime calls are removed from cti_enable_hw/cti_disable_hw. When
>> enabling CTI by writing enable sysfs node, clock for accessing CTI
>> register won't be enabled. Device will crash due to register access
>> issue. Add PM runtime call in enable_store to fix this issue.
>>
>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
>> ---
>>  drivers/hwtracing/coresight/coresight-cti-sysfs.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>> index 6d59c815ecf5..b1ed424ae043 100644
>> --- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>> +++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>> @@ -108,10 +108,17 @@ static ssize_t enable_store(struct device *dev,
>>  	if (ret)
>>  		return ret;
>>  
>> -	if (val)
>> +	if (val) {
>> +		ret = pm_runtime_resume_and_get(dev->parent);
>> +		if (ret)
>> +			return ret;
>>  		ret = cti_enable(drvdata->csdev);
>> -	else
>> +		if (ret)
>> +			pm_runtime_put(dev->parent);
>> +	} else {
>>  		ret = cti_disable(drvdata->csdev);
>> +		pm_runtime_put(dev->parent);
> 
> Hi Jinlong,
> 
> This new pm_runtime_put() causes this when writing 0 to enable:
> 
>   [  483.253814] coresight-cti 23020000.cti: Runtime PM usage count
> underflow!
> 
> Maybe we can modify cti_disable_hw() to return a value to indicate that
> the disable actually happened, and only then call pm_runtime_put().
> 
> I suppose you could also check in the store function if it was already
> enabled first, but then I don't know what kind of locking that would
> need? cti_disable_hw() already seems to have a couple of locks, so maybe
> the return value solution is easiest.
> 

We've also just seen another issue where multiple calls to
cti_disable_hw() can cause enable_req_count to go negative. I'm going to
work on a few fixes (including yours) to make sure that it's complete
and post it shortly.

James

On 1/5/2023 9:55 PM, James Clark wrote:
>
> On 04/01/2023 13:11, James Clark wrote:
>>
>> On 24/12/2022 14:17, Mao Jinlong wrote:
>>> In commit 6746eae4bbad ("coresight: cti: Fix hang in cti_disable_hw()")
>>> PM runtime calls are removed from cti_enable_hw/cti_disable_hw. When
>>> enabling CTI by writing enable sysfs node, clock for accessing CTI
>>> register won't be enabled. Device will crash due to register access
>>> issue. Add PM runtime call in enable_store to fix this issue.
>>>
>>> Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
>>> ---
>>>   drivers/hwtracing/coresight/coresight-cti-sysfs.c | 11 +++++++++--
>>>   1 file changed, 9 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>>> index 6d59c815ecf5..b1ed424ae043 100644
>>> --- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>>> +++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>>> @@ -108,10 +108,17 @@ static ssize_t enable_store(struct device *dev,
>>>   	if (ret)
>>>   		return ret;
>>>   
>>> -	if (val)
>>> +	if (val) {
>>> +		ret = pm_runtime_resume_and_get(dev->parent);
>>> +		if (ret)
>>> +			return ret;
>>>   		ret = cti_enable(drvdata->csdev);
>>> -	else
>>> +		if (ret)
>>> +			pm_runtime_put(dev->parent);
>>> +	} else {
>>>   		ret = cti_disable(drvdata->csdev);
>>> +		pm_runtime_put(dev->parent);
>> Hi Jinlong,
>>
>> This new pm_runtime_put() causes this when writing 0 to enable:
>>
>>    [  483.253814] coresight-cti 23020000.cti: Runtime PM usage count
>> underflow!
>>
>> Maybe we can modify cti_disable_hw() to return a value to indicate that
>> the disable actually happened, and only then call pm_runtime_put().
>>
>> I suppose you could also check in the store function if it was already
>> enabled first, but then I don't know what kind of locking that would
>> need? cti_disable_hw() already seems to have a couple of locks, so maybe
>> the return value solution is easiest.
>>
> We've also just seen another issue where multiple calls to
> cti_disable_hw() can cause enable_req_count to go negative. I'm going to
> work on a few fixes (including yours) to make sure that it's complete
> and post it shortly.
Ok, Thank you, James.
>
> James