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