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

From: Dmitry Osipenko
Date: Wed Oct 02 2019 - 11:27:52 EST

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In reply to: Chanwoo Choi: "Re: [PATCH v6 18/19] PM / devfreq: tegra30: Support variable polling interval"
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02.10.2019 03:18, Chanwoo Choi ÐÐÑÐÑ:
> 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.

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]

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In reply to: Chanwoo Choi: "Re: [PATCH v6 18/19] PM / devfreq: tegra30: Support variable polling interval"
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