linux-kernel - Re: [Patch v4 3/6] cpufreq: qcom-cpufreq-hw: Add dcvs interrupt support

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Date:   Wed, 28 Jul 2021 09:20:14 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org, rui.zhang@...el.com,
        daniel.lezcano@...aro.org, rjw@...ysocki.net, robh+dt@...nel.org,
        steev@...i.org, linux-arm-msm@...r.kernel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [Patch v4 3/6] cpufreq: qcom-cpufreq-hw: Add dcvs interrupt
 support

On 27-07-21, 11:25, Thara Gopinath wrote:
> +static void qcom_lmh_dcvs_notify(struct qcom_cpufreq_data *data)
> +{

> +	/* In the unlikely case cpufreq is de-registered do not enable polling or h/w interrupt */
> +
> +	spin_lock(&data->throttle_lock);
> +	if (data->cancel_throttle) {
> +		spin_unlock(&data->throttle_lock);
> +		return;
> +	}
> +	spin_unlock(&data->throttle_lock);
> +
> +	/*
> +	 * If h/w throttled frequency is higher than what cpufreq has requested for, stop
> +	 * polling and switch back to interrupt mechanism
> +	 */
> +
> +	if (throttled_freq >= qcom_cpufreq_hw_get(cpumask_first(policy->cpus)))
> +		/* Clear the existing interrupts and enable it back */
> +		enable_irq(data->throttle_irq);
> +	else
> +		mod_delayed_work(system_highpri_wq, &data->throttle_work,
> +				 msecs_to_jiffies(10));
> +}

> +static void qcom_cpufreq_hw_lmh_exit(struct qcom_cpufreq_data *data)
> +{
> +	if (data->throttle_irq <= 0)
> +		return;
> +
> +	spin_lock(&data->throttle_lock);
> +	data->cancel_throttle = true;
> +	spin_unlock(&data->throttle_lock);
> +	cancel_delayed_work_sync(&data->throttle_work);
> +	free_irq(data->throttle_irq, data);
> +}

Lets see if we can still make it break :)

CPU0                                            CPU1

qcom_lmh_dcvs_notify()                          qcom_cpufreq_hw_lmh_exit()

spin_unlock()
                                                spin_lock(),
                                                cancel_throttle = true
                                                spin_unlock()

                                                cancel_delayed_work_sync()
mod_delayed_work()
                                                free_irq()
                                                kfree(data)
qcom_lmh_dcvs_poll()
Uses data.


Sorry, locking is fun :)

-- 
viresh