[PATCH v3 20/22] PM / devfreq: tegra30: Optimize upper average watermark selection

[Dmitry Osipenko]

I noticed that CPU may be crossing the dependency threshold very
frequently for some workloads and this results in a lot of interrupts
which could be avoided if MCALL client is keeping actual EMC frequency
at a higher rate.

Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
---
 drivers/devfreq/tegra30-devfreq.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/devfreq/tegra30-devfreq.c 
b/drivers/devfreq/tegra30-devfreq.c
index 1105104445a9..5b1feaf8c16e 100644
--- a/drivers/devfreq/tegra30-devfreq.c
+++ b/drivers/devfreq/tegra30-devfreq.c
@@ -314,7 +314,8 @@ 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_threshold, lower, upper;
 
@@ -323,6 +324,15 @@ static void tegra_devfreq_update_avg_wmark(struct 
tegra_devfreq *tegra,
        avg_threshold = dev->config->avg_dependency_threshold;
        avg_threshold = avg_threshold * ACTMON_SAMPLING_PERIOD;
 
+       /*
+        * If cumulative EMC frequency selection 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.
+        */
+       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
@@ -392,6 +402,7 @@ 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;
 
        trace_device_isr_enter(tegra->regs, dev->config->offset,
                               dev->boost_freq, cpufreq_get(0));
@@ -405,8 +416,10 @@ 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) {
                /*
@@ -524,7 +537,7 @@ static int tegra_actmon_clk_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);
        }
 
@@ -629,7 +642,7 @@ 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