Re: [PATCH v8 16/18] PM / devfreq: tegra30: Support variable polling interval

From: Chanwoo Choi <cw00.choi@samsung.com>
To: "Dmitry Osipenko" <digetx@gmail.com>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"MyungJoo Ham" <myungjoo.ham@samsung.com>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"Jonathan Hunter" <jonathanh@nvidia.com>,
	"Tomeu Vizoso" <tomeu.vizoso@collabora.com>,
	"Peter Geis" <pgwipeout@gmail.com>,
	"Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 16/18] PM / devfreq: tegra30: Support variable polling interval
Date: Mon, 4 Nov 2019 11:53:23 +0900	[thread overview]
Message-ID: <e3967b07-b53f-0d9c-8f1b-bad238c4ef68@samsung.com> (raw)
In-Reply-To: <20191103204130.2172-17-digetx@gmail.com>

On 19. 11. 4. 오전 5:41, 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@gmail.com>
> ---
>  drivers/devfreq/tegra30-devfreq.c | 83 +++++++++++++++++++++++--------
>  1 file changed, 61 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
> index 852bde6249c7..9c645e83ef8b 100644
> --- a/drivers/devfreq/tegra30-devfreq.c
> +++ b/drivers/devfreq/tegra30-devfreq.c
> @@ -96,9 +96,10 @@ struct tegra_devfreq_device_config {
>  	unsigned int	boost_down_threshold;
>  
>  	/*
> -	 * Threshold of activity (cycles) below which the CPU frequency isn't
> -	 * to be taken into account. This is to avoid increasing the EMC
> -	 * frequency when the CPU is very busy but not accessing the bus often.
> +	 * Threshold of activity (cycles translated to kHz) below which the
> +	 * CPU frequency isn't to be taken into account. This is to avoid
> +	 * increasing the EMC frequency when the CPU is very busy but not
> +	 * accessing the bus often.
>  	 */
>  	u32		avg_dependency_threshold;
>  };
> @@ -126,7 +127,7 @@ static const struct tegra_devfreq_device_config actmon_device_configs[] = {
>  		.boost_down_coeff = 90,
>  		.boost_up_threshold = 27,
>  		.boost_down_threshold = 10,
> -		.avg_dependency_threshold = 50000,
> +		.avg_dependency_threshold = 5 * KHZ,

nitpick.
Actually, this change is not related to this patch.
Even if it is trivial, it is not proper.

>  	},
>  };
>  
> @@ -208,9 +209,16 @@ static void device_writel(struct tegra_devfreq_device *dev, u32 val,
>  	writel_relaxed(val, dev->regs + offset);
>  }
>  
> -static unsigned long do_percent(unsigned long val, unsigned int pct)
> +static unsigned long do_percent(unsigned long long val, unsigned int pct)
>  {
> -	return val * pct / 100;
> +	val = val * pct;
> +	do_div(val, 100);
> +
> +	/*
> +	 * High freq + high boosting percent + large polling interval are
> +	 * resulting in integer overflow when watermarks are calculated.
> +	 */
> +	return min_t(u64, val, U32_MAX);
>  }
>  
>  static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
> @@ -218,8 +226,9 @@ static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
>  {
>  	u32 avg = dev->avg_count;
>  	u32 avg_band_freq = tegra->max_freq * ACTMON_DEFAULT_AVG_BAND / KHZ;
> -	u32 band = avg_band_freq * ACTMON_SAMPLING_PERIOD;
> +	u32 band = avg_band_freq * tegra->devfreq->profile->polling_ms;
>  
> +	avg = min(dev->avg_count, U32_MAX - band);
>  	device_writel(dev, avg + band, ACTMON_DEV_AVG_UPPER_WMARK);
>  
>  	avg = max(dev->avg_count, band);
> @@ -229,7 +238,7 @@ static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
>  static void tegra_devfreq_update_wmark(struct tegra_devfreq *tegra,
>  				       struct tegra_devfreq_device *dev)
>  {
> -	u32 val = tegra->cur_freq * ACTMON_SAMPLING_PERIOD;
> +	u32 val = tegra->cur_freq * tegra->devfreq->profile->polling_ms;
>  
>  	device_writel(dev, do_percent(val, dev->config->boost_up_threshold),
>  		      ACTMON_DEV_UPPER_WMARK);
> @@ -308,10 +317,9 @@ static unsigned long actmon_device_target_freq(struct tegra_devfreq *tegra,
>  	unsigned int avg_sustain_coef;
>  	unsigned long target_freq;
>  
> -	target_freq = dev->avg_count / ACTMON_SAMPLING_PERIOD;
> +	target_freq = dev->avg_count / tegra->devfreq->profile->polling_ms;
>  	avg_sustain_coef = 100 * 100 / dev->config->boost_up_threshold;
>  	target_freq = do_percent(target_freq, avg_sustain_coef);
> -	target_freq += dev->boost_freq;
>  
>  	return target_freq;
>  }
> @@ -322,15 +330,18 @@ static void actmon_update_target(struct tegra_devfreq *tegra,
>  	unsigned long cpu_freq = 0;
>  	unsigned long static_cpu_emc_freq = 0;
>  
> -	if (dev->config->avg_dependency_threshold) {
> +	dev->target_freq = actmon_device_target_freq(tegra, dev);
> +
> +	if (dev->config->avg_dependency_threshold &&
> +	    dev->config->avg_dependency_threshold <= dev->target_freq) {

This changes are related to polling interval change at the run time?
This patch touched the 'avg_dependency_threshold'. It is related to the 
dynamic change of polling interval?

>  		cpu_freq = cpufreq_quick_get(0);
>  		static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpu_freq);
> -	}
>  
> -	dev->target_freq = actmon_device_target_freq(tegra, dev);
> -
> -	if (dev->avg_count >= dev->config->avg_dependency_threshold)
> +		dev->target_freq += dev->boost_freq;
>  		dev->target_freq = max(dev->target_freq, static_cpu_emc_freq);
> +	} else {
> +		dev->target_freq += dev->boost_freq;
> +	}

ditto. This changes are related to polling interval change at the run time?

>  }
>  
>  static irqreturn_t actmon_thread_isr(int irq, void *data)
> @@ -396,15 +407,16 @@ static unsigned long
>  tegra_actmon_cpufreq_contribution(struct tegra_devfreq *tegra,
>  				  unsigned int cpu_freq)
>  {
> +	struct tegra_devfreq_device *dev = &tegra->devices[MCCPU];
>  	unsigned long static_cpu_emc_freq, dev_freq;
>  
> +	dev_freq = actmon_device_target_freq(tegra, dev);
> +
>  	/* check whether CPU's freq is taken into account at all */
> -	if (tegra->devices[MCCPU].avg_count <
> -	    tegra->devices[MCCPU].config->avg_dependency_threshold)
> +	if (dev_freq < dev->config->avg_dependency_threshold)

ditto.

>  		return 0;
>  
>  	static_cpu_emc_freq = actmon_cpu_to_emc_rate(tegra, cpu_freq);
> -	dev_freq = actmon_device_target_freq(tegra, &tegra->devices[MCCPU]);
>  
>  	if (dev_freq >= static_cpu_emc_freq)
>  		return 0;
> @@ -465,7 +477,7 @@ static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
>  
>  	dev->target_freq = tegra->cur_freq;
>  
> -	dev->avg_count = tegra->cur_freq * ACTMON_SAMPLING_PERIOD;
> +	dev->avg_count = tegra->cur_freq * tegra->devfreq->profile->polling_ms;
>  	device_writel(dev, dev->avg_count, ACTMON_DEV_INIT_AVG);
>  
>  	tegra_devfreq_update_avg_wmark(tegra, dev);
> @@ -506,7 +518,10 @@ static int tegra_actmon_start(struct tegra_devfreq *tegra)
>  	unsigned int i;
>  	int err;
>  
> -	actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
> +	if (!tegra->devfreq->profile->polling_ms || tegra->cur_freq)
> +		return 0;
> +
> +	actmon_writel(tegra, tegra->devfreq->profile->polling_ms - 1,
>  		      ACTMON_GLB_PERIOD_CTRL);
>  
>  	/*
> @@ -551,11 +566,16 @@ static int tegra_actmon_start(struct tegra_devfreq *tegra)
>  
>  	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
>  
> +	tegra->cur_freq = 0;
> +
>  	return err;
>  }
>  
>  static void tegra_actmon_stop(struct tegra_devfreq *tegra)
>  {
> +	if (!tegra->devfreq->profile->polling_ms || !tegra->cur_freq)
> +		return;
> +
>  	disable_irq(tegra->irq);
>  
>  	cpufreq_unregister_notifier(&tegra->cpu_rate_change_nb,
> @@ -566,6 +586,8 @@ static void tegra_actmon_stop(struct tegra_devfreq *tegra)
>  	tegra_actmon_stop_devices(tegra);
>  
>  	clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
> +
> +	tegra->cur_freq = 0;
>  }
>  
>  static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
> @@ -625,7 +647,7 @@ 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 = ACTMON_SAMPLING_PERIOD * cur_freq;
> +	stat->total_time = tegra->devfreq->profile->polling_ms * cur_freq;
>  
>  	stat->busy_time = min(stat->busy_time, stat->total_time);
>  
> @@ -633,7 +655,7 @@ 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,
>  };
> @@ -673,6 +695,7 @@ 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 = data;
>  	int ret = 0;
>  
>  	/*
> @@ -692,6 +715,21 @@ static int tegra_governor_event_handler(struct devfreq *devfreq,
>  		devfreq_monitor_stop(devfreq);
>  		break;
>  
> +	case DEVFREQ_GOV_INTERVAL:
> +		/*
> +		 * ACTMON hardware supports up to 256 milliseconds for the
> +		 * sampling period.
> +		 */
> +		if (*new_delay > 256) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +
> +		tegra_actmon_stop(tegra);
> +		devfreq_interval_update(devfreq, new_delay);
> +		ret = tegra_actmon_start(tegra);
> +		break;
> +
>  	case DEVFREQ_GOV_SUSPEND:
>  		tegra_actmon_stop(tegra);
>  		devfreq_monitor_suspend(devfreq);
> @@ -711,6 +749,7 @@ static struct devfreq_governor tegra_devfreq_governor = {
>  	.get_target_freq = tegra_governor_get_target,
>  	.event_handler = tegra_governor_event_handler,
>  	.immutable = true,
> +	.interrupt_driven = true,
>  };
>  
>  static int tegra_devfreq_probe(struct platform_device *pdev)
> 

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics