Re: [PATCH v6 18/19] PM / devfreq: tegra30: Support variable polling interval

[Chanwoo Choi]

Hi,

On 19. 8. 12. ìì 6:23, Dmitry Osipenko wrote:
> The ACTMON governor is interrupt-driven and currently hardware's polling
> interval is fixed to 16ms in the driver. Devfreq supports variable polling
> interval by the generic governors, let's re-use the generic interface for
> changing of the polling interval. Now the polling interval can be changed
> dynamically via /sys/class/devfreq/devfreq0/polling_interval.
> 
> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
> ---
>  drivers/devfreq/tegra30-devfreq.c | 71 ++++++++++++++++++++++---------
>  1 file changed, 50 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
> index 8adc0ff48b45..e30314bd571a 100644
> --- a/drivers/devfreq/tegra30-devfreq.c
> +++ b/drivers/devfreq/tegra30-devfreq.c
> @@ -12,6 +12,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/io.h>
>  #include <linux/irq.h>
> +#include <linux/jiffies.h>
>  #include <linux/module.h>
>  #include <linux/of_device.h>
>  #include <linux/platform_device.h>
> @@ -236,7 +237,7 @@ tegra_actmon_dev_avg_dependency_freq(struct tegra_devfreq *tegra,
>  				     struct tegra_devfreq_device *dev)
>  {
>  	return dev->config->avg_dependency_threshold /
> -		ACTMON_SAMPLING_PERIOD;
> +		tegra->devfreq->profile->polling_ms;
>  }
>  
>  static unsigned long
> @@ -314,8 +315,8 @@ static void tegra_actmon_get_lower_upper(struct tegra_devfreq *tegra,
>  	 */
>  	*upper = tegra_actmon_account_cpu_freq(tegra, dev, *upper);
>  
> -	*lower *= ACTMON_SAMPLING_PERIOD;
> -	*upper *= ACTMON_SAMPLING_PERIOD;
> +	*lower *= tegra->devfreq->profile->polling_ms;
> +	*upper *= tegra->devfreq->profile->polling_ms;
>  }
>  
>  static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
> @@ -341,8 +342,8 @@ static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
>  	 * result, but this one is probably the least churning, although
>  	 * it may look a bit convoluted.
>  	 */
> -	if (freq * ACTMON_SAMPLING_PERIOD > upper)
> -		upper = freq * ACTMON_SAMPLING_PERIOD;
> +	if (freq * tegra->devfreq->profile->polling_ms > upper)
> +		upper = freq * tegra->devfreq->profile->polling_ms;
>  
>  	/*
>  	 * We want to get interrupts when MCCPU client crosses the
> @@ -420,7 +421,7 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
>  	avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
>  	dev_ctrl = device_readl(dev, ACTMON_DEV_CTRL);
>  
> -	dev->avg_freq = avg_count / ACTMON_SAMPLING_PERIOD;
> +	dev->avg_freq = avg_count / tegra->devfreq->profile->polling_ms;
>  
>  	avg_intr_mask = ACTMON_DEV_INTR_AVG_BELOW_WMARK |
>  			ACTMON_DEV_INTR_AVG_ABOVE_WMARK;
> @@ -499,7 +500,7 @@ static unsigned long actmon_update_target(struct tegra_devfreq *tegra,
>  	 * outdated.
>  	 */
>  	avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
> -	avg_freq = avg_count / ACTMON_SAMPLING_PERIOD;
> +	avg_freq = avg_count / tegra->devfreq->profile->polling_ms;
>  
>  	old_upper = tegra_actmon_upper_freq(tegra, dev->avg_freq);
>  	new_upper = tegra_actmon_upper_freq(tegra, avg_freq);
> @@ -675,7 +676,7 @@ static int tegra_actmon_cpu_notify_cb(struct notifier_block *nb,
>  	 * here for too long, otherwise CPUFreq's core will complain with a
>  	 * warning splat.
>  	 */
> -	delay = msecs_to_jiffies(ACTMON_SAMPLING_PERIOD);
> +	delay = msecs_to_jiffies(tegra->devfreq->profile->polling_ms);
>  	schedule_delayed_work(&tegra->cpufreq_update_work, delay);
>  
>  	return NOTIFY_OK;
> @@ -690,7 +691,7 @@ static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
>  	dev->boost_freq = 0;
>  
>  	dev->avg_freq = clk_get_rate(tegra->emc_clock) / KHZ;
> -	device_writel(dev, dev->avg_freq * ACTMON_SAMPLING_PERIOD,
> +	device_writel(dev, dev->avg_freq * tegra->devfreq->profile->polling_ms,
>  		      ACTMON_DEV_INIT_AVG);
>  
>  	tegra_devfreq_update_avg_wmark(tegra, dev, dev->avg_freq);
> @@ -725,7 +726,14 @@ static int tegra_actmon_start(struct tegra_devfreq *tegra)
>  	unsigned int i;
>  	int err;
>  
> -	actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
> +	if (!tegra->devfreq->stop_polling)

I don't prefer to change the 'stop_polling' on each device driver direclty
without devfreq interface. Don't access it directly.

> +		return 0;
> +
> +	tegra->devfreq->previous_freq = clk_get_rate(tegra->emc_clock) / KHZ;
> +	tegra->devfreq->last_stat_updated = jiffies;
> +	tegra->devfreq->stop_polling = false;

ditto.

> +
> +	actmon_writel(tegra, tegra->devfreq->profile->polling_ms - 1,
>  		      ACTMON_GLB_PERIOD_CTRL);
>  
>  	/*
> @@ -776,6 +784,11 @@ static void tegra_actmon_stop(struct tegra_devfreq *tegra)
>  {
>  	unsigned int i;
>  
> +	if (tegra->devfreq->stop_polling)

ditto.

> +		return;
> +
> +	mutex_unlock(&tegra->devfreq->lock);
> +
>  	disable_irq(tegra->irq);
>  
>  	cpufreq_unregister_notifier(&tegra->cpu_rate_change_nb,
> @@ -783,10 +796,16 @@ static void tegra_actmon_stop(struct tegra_devfreq *tegra)
>  
>  	cancel_delayed_work_sync(&tegra->cpufreq_update_work);
>  
> +	mutex_lock(&tegra->devfreq->lock);
> +
>  	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
>  		tegra_actmon_stop_device(&tegra->devices[i]);
>  
>  	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
> +
> +	devfreq_update_status(tegra->devfreq, tegra->devfreq->previous_freq);
> +
> +	tegra->devfreq->stop_polling = true;

ditto.

>  }
>  
>  static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
> @@ -846,7 +865,7 @@ static int tegra_devfreq_get_dev_status(struct device *dev,
>  	stat->busy_time *= 100 / BUS_SATURATION_RATIO;
>  
>  	/* Number of cycles in a sampling period */
> -	stat->total_time = cur_freq * ACTMON_SAMPLING_PERIOD;
> +	stat->total_time = cur_freq * tegra->devfreq->profile->polling_ms;
>  
>  	stat->busy_time = min(stat->busy_time, stat->total_time);
>  
> @@ -854,7 +873,7 @@ static int tegra_devfreq_get_dev_status(struct device *dev,
>  }
>  
>  static struct devfreq_dev_profile tegra_devfreq_profile = {
> -	.polling_ms	= 0,
> +	.polling_ms	= ACTMON_SAMPLING_PERIOD,
>  	.target		= tegra_devfreq_target,
>  	.get_dev_status	= tegra_devfreq_get_dev_status,
>  };
> @@ -895,8 +914,11 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
>  					unsigned int event, void *data)
>  {
>  	struct tegra_devfreq *tegra = dev_get_drvdata(devfreq->dev.parent);
> +	unsigned int new_delay, *delay_ptr = data;
>  	int ret = 0;
>  
> +	mutex_lock(&devfreq->lock);
> +
>  	/*
>  	 * Couple device with the governor early as it is needed at
>  	 * the moment of governor's start (used by ISR).
> @@ -905,26 +927,33 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
>  
>  	switch (event) {
>  	case DEVFREQ_GOV_START:
> -		devfreq_monitor_start(devfreq);
> +		devfreq->stop_polling = true;

It is not proper to initialize the 'stop_polling' on device driver directly.

> +		/* fall through */
> +	case DEVFREQ_GOV_RESUME:
>  		ret = tegra_actmon_start(tegra);
>  		break;
>  
>  	case DEVFREQ_GOV_STOP:
> -		tegra_actmon_stop(tegra);
> -		devfreq_monitor_stop(devfreq);

Why do you remove them?

> -		break;
> -
> +		/* fall through */
>  	case DEVFREQ_GOV_SUSPEND:
>  		tegra_actmon_stop(tegra);
> -		devfreq_monitor_suspend(devfreq);

Why do you remove it?

>  		break;
>  
> -	case DEVFREQ_GOV_RESUME:
> -		devfreq_monitor_resume(devfreq);
> -		ret = tegra_actmon_start(tegra);
> +	case DEVFREQ_GOV_INTERVAL:
> +		new_delay = *delay_ptr;
> +
> +		if (!new_delay || new_delay > 256) {
> +			ret = -EINVAL;
> +		} else {
> +			tegra_actmon_stop(tegra);
> +			devfreq->profile->polling_ms = new_delay;
> +			ret = tegra_actmon_start(tegra);
> +		}
>  		break;
>  	}
>  
> +	mutex_unlock(&devfreq->lock);
> +
>  	return ret;
>  }
>  
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics