On 7/9/21 2:46 AM, Viresh Kumar wrote:

On 08-07-21, 08:06, Thara Gopinath wrote:

quoted

  static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
  {
  	struct platform_device *pdev = cpufreq_get_driver_data();

@@ -370,6 +480,10 @@ static int qcom_cpufreq_hw_cpu_init(struct cpufreq_policy *policy)
  			dev_warn(cpu_dev, "failed to enable boost: %d\n", ret);
  	}
  
+	ret = qcom_cpufreq_hw_lmh_init(policy, index);

You missed unregistering EM here (which is also missing from exit,
which you need to fix first in a separate patch).

Hi!

So how exactly do you do this? I checked other users of the api and I do 
not see any free. I would say if needed, it should be a separate patch 
and outside of this series.

quoted

+	if (ret)
+		goto error;
+
  	return 0;
  error:
  	kfree(data);

@@ -389,6 +503,10 @@ static int qcom_cpufreq_hw_cpu_exit(struct cpufreq_policy *policy)
  
  	dev_pm_opp_remove_all_dynamic(cpu_dev);
  	dev_pm_opp_of_cpumask_remove_table(policy->related_cpus);
+	if (data->lmh_dcvs_irq > 0) {
+		devm_free_irq(cpu_dev, data->lmh_dcvs_irq, data);

Why using devm variants here and while requesting the irq ?

quoted

+		cancel_delayed_work_sync(&data->lmh_dcvs_poll_work);
+	}

Please move this to qcom_cpufreq_hw_lmh_exit() or something.

Ok.

Now with sequence of disabling interrupt, etc, I see a potential
problem.

CPU0                                    CPU1

qcom_cpufreq_hw_cpu_exit()
-> devm_free_irq();
                                         qcom_lmh_dcvs_poll()
                                         -> qcom_lmh_dcvs_notify()
                                           -> enable_irq()

-> cancel_delayed_work_sync();


What will happen if enable_irq() gets called after freeing the irq ?
Not sure, but it looks like you will hit this then from manage.c:

WARN(!desc->irq_data.chip, KERN_ERR "enable_irq before
                                      setup/request_irq: irq %u\n", irq))

?

You got a chicken n egg problem :)

Yes indeed! But also it is a very rare chicken and egg problem.
The scenario here is that the cpus are busy and running load causing a 
thermal overrun and lmh is engaged. At the same time for this issue to 
be hit the cpu is trying to exit/disable cpufreq. Calling 
cancel_delayed_work_sync first could solve this issue, right ? 
cancel_delayed_work_sync guarantees the work not to be pending even if
it requeues itself on return. So once the delayed work is cancelled, the 
interrupts can be safely disabled. Thoughts ?

-- 
Warm Regards
Thara (She/Her/Hers)