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

[Dmitry Osipenko]

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 | 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,
 	},
 };
 
@@ -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) {
 		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;
+	}
 }
 
 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)
 		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)
-- 
2.23.0