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From: Dmitry Osipenko <digetx@gmail.com>
To: Chanwoo Choi <cw00.choi@samsung.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>
Cc: linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 18/19] PM / devfreq: tegra30: Support variable polling interval
Date: Wed, 2 Oct 2019 18:27:45 +0300
Message-ID: <a800b077-3d01-78d8-2fb4-bec82c796b45@gmail.com> (raw)
In-Reply-To: <721c4dd0-d667-f83d-64b5-74e4b58a7a1c@samsung.com>

02.10.2019 03:18, Chanwoo Choi пишет:
> Hi,
> 
> On 19. 8. 12. 오전 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@gmail.com>
>> ---
>>  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.

Hmm.. okay. Please see more comments below.

>> +		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?

Becasue DEVFREQ_GOV_STOP and DEVFREQ_GOV_SUSPEND are doing the same now:

	case DEVFREQ_GOV_STOP:
		/* fall through */
	case DEVFREQ_GOV_SUSPEND:
		tegra_actmon_stop(tegra);
		break;

>> -		break;
>> -
>> +		/* fall through */
>>  	case DEVFREQ_GOV_SUSPEND:
>>  		tegra_actmon_stop(tegra);
>> -		devfreq_monitor_suspend(devfreq);
> 
> Why do you remove it?

a) it takes the same mutex devfreq->lock as tegra_governor_event_handler()
b) the devfreq's manual polling isn't needed for this driver and thus
devfreq->work is unwanted
c) this patch makes tegra_actmon_stop() to replicate what
devfreq_monitor_suspend() does

It looks like it will be better to add new generic events for the
governors, like DEVFREQ_GOV_START/STOP_POLLING. Then this driver will be
able to customize start/stop of the polling, while software governors
will utilize some new default helpers that will start/stop the polling
work. What do you think?

[snip]

  reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-11 21:22 [PATCH v6 00/19] More improvements for Tegra30 devfreq driver Dmitry Osipenko
2019-08-11 21:22 ` [PATCH v6 01/19] PM / devfreq: tegra30: Change irq type to unsigned int Dmitry Osipenko
2019-08-11 21:22 ` [PATCH v6 02/19] PM / devfreq: tegra30: Keep interrupt disabled while governor is stopped Dmitry Osipenko
2019-08-20  0:02   ` Chanwoo Choi
2019-08-11 21:22 ` [PATCH v6 03/19] PM / devfreq: tegra30: Handle possible round-rate error Dmitry Osipenko
2019-08-20  0:06   ` Chanwoo Choi
2019-08-11 21:23 ` [PATCH v6 04/19] PM / devfreq: tegra30: Drop write-barrier Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 05/19] PM / devfreq: tegra30: Set up watermarks properly Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 06/19] PM / devfreq: tegra30: Tune up boosting thresholds Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 07/19] PM / devfreq: tegra30: Fix integer overflow on CPU's freq max out Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 08/19] PM / devfreq: tegra30: Ensure that target freq won't overflow Dmitry Osipenko
2019-08-20  0:23   ` Chanwoo Choi
2019-08-20 23:19     ` Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 09/19] PM / devfreq: tegra30: Use kHz units uniformly in the code Dmitry Osipenko
2019-10-01 23:29   ` Chanwoo Choi
2019-10-02 18:26     ` Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 10/19] PM / devfreq: tegra30: Reduce unnecessary interrupts activity Dmitry Osipenko
2019-10-01 23:35   ` Chanwoo Choi
2019-10-02 18:40     ` Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 11/19] PM / devfreq: tegra30: Use CPUFreq notifier Dmitry Osipenko
2019-10-02  0:02   ` Chanwoo Choi
2019-10-02 14:06     ` Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 12/19] PM / devfreq: tegra30: Move clk-notifier's registration to governor's start Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 13/19] PM / devfreq: tegra30: Reset boosting on startup Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 14/19] PM / devfreq: tegra30: Don't enable consecutive-down interrupt " Dmitry Osipenko
2019-10-02  0:04   ` Chanwoo Choi
2019-08-11 21:23 ` [PATCH v6 15/19] PM / devfreq: tegra30: Constify structs Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 16/19] PM / devfreq: tegra30: Include appropriate header Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 17/19] PM / devfreq: tegra30: Increase sampling period to 16ms Dmitry Osipenko
2019-08-11 21:23 ` [PATCH v6 18/19] PM / devfreq: tegra30: Support variable polling interval Dmitry Osipenko
2019-10-02  0:18   ` Chanwoo Choi
2019-10-02 15:27     ` Dmitry Osipenko [this message]
2019-08-11 21:23 ` [PATCH v6 19/19] PM / devfreq: tegra20/30: Add Dmitry as a maintainer Dmitry Osipenko
2019-10-01 21:15 ` [PATCH v6 00/19] More improvements for Tegra30 devfreq driver Dmitry Osipenko
2019-10-02  0:25   ` Chanwoo Choi
2019-10-02 13:54     ` Dmitry Osipenko
2019-10-05 16:29       ` Peter Geis

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