linux-kernel - [PATCH v4 19/24] PM / devfreq: tegra30: Optimize upper consecutive watermark selection

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Date:   Mon,  8 Jul 2019 01:32:58 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:     linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v4 19/24] PM / devfreq: tegra30: Optimize upper consecutive watermark selection

The memory activity counter may get a bit higher than a watermark which
is selected based on OPP that corresponds to a highest EMC rate, in this
case watermark is lower than the actual memory activity is and thus
results in unwanted "upper" interrupts.

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/devfreq/tegra30-devfreq.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/devfreq/tegra30-devfreq.c b/drivers/devfreq/tegra30-devfreq.c
index 8d6bf6e9f1ae..c3cf87231d25 100644
--- a/drivers/devfreq/tegra30-devfreq.c
+++ b/drivers/devfreq/tegra30-devfreq.c
@@ -363,7 +363,18 @@ 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
-- 
2.22.0