[PATCH v6 10/19] PM / devfreq: tegra30: Reduce unnecessary interrupts activity

[Dmitry Osipenko]

There are cases where unnecessary ACTMON interrupts could be avoided,
like when one memory client device requests higher clock rate than the
other or when clock rate is manually limited using sysfs devfreq
parameters. These cases could be avoided by tuning upper watermark or
disabling hardware events when min/max boosting thresholds are reached.

Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
---
 drivers/devfreq/tegra30-devfreq.c | 87 ++++++++++++++++++++++++++++---
 1 file changed, 80 insertions(+), 7 deletions(-)

diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
index 43d50b4366dd..a2623de56d20 100644
--- a/drivers/devfreq/tegra30-devfreq.c
+++ b/drivers/devfreq/tegra30-devfreq.c
@@ -312,7 +312,8 @@ static void tegra_actmon_get_lower_upper(struct tegra_devfreq *tegra,
 }
 
 static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
-					   struct tegra_devfreq_device *dev)
+					   struct tegra_devfreq_device *dev,
+					   unsigned long freq)
 {
 	unsigned long avg_dependency_freq, lower, upper;
 
@@ -320,6 +321,22 @@ static void tegra_devfreq_update_avg_wmark(struct tegra_devfreq *tegra,
 
 	avg_dependency_freq = tegra_actmon_dev_avg_dependency_freq(tegra, dev);
 
+	/*
+	 * If cumulative EMC frequency selection (MCALL / min_freq) is
+	 * higher than the device's, then there is no need to set upper
+	 * watermark to a lower value because it will result in unnecessary
+	 * upper interrupts.
+	 *
+	 * Note that average watermarks are also updated after EMC
+	 * clock rate change, hence if clock rate goes down, then the
+	 * watermarks will be set in accordance to the new rate after
+	 * changing the rate. There are other ways to achieve the same
+	 * 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;
+
 	/*
 	 * We want to get interrupts when MCCPU client crosses the
 	 * dependency threshold in order to take into / out of account
@@ -361,7 +378,18 @@ static void tegra_devfreq_update_wmark(struct tegra_devfreq *tegra,
 	tegra_actmon_get_lower_upper(tegra, dev, freq - 1, &lower, &upper);
 
 	delta = do_percent(upper - lower, dev->config->boost_up_threshold);
-	device_writel(dev, lower + delta, ACTMON_DEV_UPPER_WMARK);
+
+	/*
+	 * The memory events count could go a bit higher than the maximum
+	 * defined by the OPPs, hence make the upper watermark infinitely
+	 * high to avoid unnecessary upper interrupts in that case.
+	 */
+	if (freq == tegra->max_freq)
+		upper = ULONG_MAX;
+	else
+		upper = lower + delta;
+
+	device_writel(dev, upper, ACTMON_DEV_UPPER_WMARK);
 
 	/*
 	 * Meanwhile the lower mark is based on the average value
@@ -379,6 +407,7 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
 			      struct tegra_devfreq_device *dev)
 {
 	u32 intr_status, dev_ctrl, avg_intr_mask, avg_count;
+	unsigned long freq;
 
 	intr_status = device_readl(dev, ACTMON_DEV_INTR_STATUS);
 	avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
@@ -389,8 +418,10 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
 	avg_intr_mask = ACTMON_DEV_INTR_AVG_BELOW_WMARK |
 			ACTMON_DEV_INTR_AVG_ABOVE_WMARK;
 
-	if (intr_status & avg_intr_mask)
-		tegra_devfreq_update_avg_wmark(tegra, dev);
+	if (intr_status & avg_intr_mask) {
+		freq = clk_get_rate(tegra->emc_clock) / KHZ;
+		tegra_devfreq_update_avg_wmark(tegra, dev, freq);
+	}
 
 	if (intr_status & ACTMON_DEV_INTR_CONSECUTIVE_UPPER) {
 		/*
@@ -412,6 +443,8 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
 		dev->boost_freq = do_percent(dev->boost_freq,
 					     dev->config->boost_down_coeff);
 
+		dev_ctrl |= ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
+
 		if (dev->boost_freq < (ACTMON_BOOST_FREQ_STEP >> 1))
 			dev->boost_freq = 0;
 	}
@@ -427,8 +460,16 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
 	}
 
 	/* no boosting => no need for consecutive-down interrupt */
-	if (dev->boost_freq == 0)
+	if (dev->boost_freq == 0) {
 		dev_ctrl &= ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+		dev_ctrl |= ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
+	}
+
+	/* boosting max-out => no need for consecutive-up interrupt */
+	if (dev->boost_freq == tegra->max_freq) {
+		dev_ctrl &= ~ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
+		dev_ctrl |= ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+	}
 
 	device_writel(dev, dev_ctrl, ACTMON_DEV_CTRL);
 	device_writel(dev, ACTMON_INTR_STATUS_CLEAR, ACTMON_DEV_INTR_STATUS);
@@ -437,8 +478,40 @@ static void actmon_isr_device(struct tegra_devfreq *tegra,
 static unsigned long actmon_update_target(struct tegra_devfreq *tegra,
 					  struct tegra_devfreq_device *dev)
 {
+	u32 avg_count, avg_freq, old_upper, new_upper, dev_ctrl;
 	unsigned long target_freq;
 
+	/*
+	 * The avg_count / avg_freq is getting snapshoted on device's
+	 * interrupt, but there are cases where actual value need to
+	 * be utilized on target's update, like CPUFreq boosting and
+	 * overriding the min freq via /sys/class/devfreq/devfreq0/min_freq
+	 * because we're optimizing the upper watermark based on the
+	 * actual EMC frequency. This means that interrupt may be
+	 * inactive for a long time and thus making snapshoted value
+	 * outdated.
+	 */
+	avg_count = device_readl(dev, ACTMON_DEV_AVG_COUNT);
+	avg_freq = avg_count / ACTMON_SAMPLING_PERIOD;
+
+	old_upper = tegra_actmon_upper_freq(tegra, dev->avg_freq);
+	new_upper = tegra_actmon_upper_freq(tegra, avg_freq);
+
+	/* similar to ISR, see comments in actmon_isr_device() */
+	if (old_upper != new_upper) {
+		if (dev->boost_freq == tegra->max_freq) {
+			dev_ctrl = device_readl(dev, ACTMON_DEV_CTRL);
+
+			dev_ctrl &= ~ACTMON_DEV_CTRL_CONSECUTIVE_BELOW_WMARK_EN;
+			dev_ctrl |= ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
+
+			device_writel(dev, dev_ctrl, ACTMON_DEV_CTRL);
+		}
+
+		dev->avg_freq = avg_freq;
+		dev->boost_freq = 0;
+	}
+
 	target_freq = dev->avg_freq + dev->boost_freq;
 	target_freq = tegra_actmon_account_cpu_freq(tegra, dev, target_freq);
 
@@ -506,7 +579,7 @@ static int tegra_actmon_rate_notify_cb(struct notifier_block *nb,
 	for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
 		dev = &tegra->devices[i];
 
-		tegra_devfreq_update_avg_wmark(tegra, dev);
+		tegra_devfreq_update_avg_wmark(tegra, dev, freq);
 		tegra_devfreq_update_wmark(tegra, dev, freq);
 	}
 
@@ -522,7 +595,7 @@ static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
 	device_writel(dev, dev->avg_freq * ACTMON_SAMPLING_PERIOD,
 		      ACTMON_DEV_INIT_AVG);
 
-	tegra_devfreq_update_avg_wmark(tegra, dev);
+	tegra_devfreq_update_avg_wmark(tegra, dev, dev->avg_freq);
 	tegra_devfreq_update_wmark(tegra, dev, dev->avg_freq);
 
 	device_writel(dev, ACTMON_COUNT_WEIGHT, ACTMON_DEV_COUNT_WEIGHT);
-- 
2.22.0