linux-kernel - [PATCH v4 2/5] thermal: devfreq_cooling: use a copy of device status

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Message-Id: <20201210143014.24685-3-lukasz.luba@arm.com>
Date:   Thu, 10 Dec 2020 14:30:11 +0000
From:   Lukasz Luba <lukasz.luba@....com>
To:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Cc:     rui.zhang@...el.com, amit.kucheria@...durent.com,
        daniel.lezcano@...aro.org, lukasz.luba@....com, orjan.eide@....com,
        robh@...nel.org, alyssa.rosenzweig@...labora.com,
        steven.price@....com, airlied@...ux.ie, daniel@...ll.ch,
        ionela.voinescu@....com
Subject: [PATCH v4 2/5] thermal: devfreq_cooling: use a copy of device status

Devfreq cooling needs to now the correct status of the device in order
to operate. Devfreq framework can change the device status in the
background. To mitigate issues make a copy of the status structure and use
it for internal calculations.

In addition this patch adds normalization function, which also makes sure
that whatever data comes from the device, the load will be in range from 1
to 1024.

Reviewed-by: Ionela Voinescu <ionela.voinescu@....com>
Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
 drivers/thermal/devfreq_cooling.c | 47 ++++++++++++++++++++++++-------
 1 file changed, 37 insertions(+), 10 deletions(-)

diff --git a/drivers/thermal/devfreq_cooling.c b/drivers/thermal/devfreq_cooling.c
index 659c0143c9f0..afcebadbad24 100644
--- a/drivers/thermal/devfreq_cooling.c
+++ b/drivers/thermal/devfreq_cooling.c
@@ -227,20 +227,39 @@ static inline unsigned long get_total_power(struct devfreq_cooling_device *dfc,
 							       voltage);
 }
 
+static void _normalize_load(struct devfreq_dev_status *status)
+{
+	if (status->total_time > 0xfffff) {
+		status->total_time >>= 10;
+		status->busy_time >>= 10;
+	}
+
+	status->busy_time <<= 10;
+	status->busy_time /= status->total_time ? : 1;
+
+	status->busy_time = status->busy_time ? : 1;
+	status->total_time = 1024;
+}
 
 static int devfreq_cooling_get_requested_power(struct thermal_cooling_device *cdev,
 					       u32 *power)
 {
 	struct devfreq_cooling_device *dfc = cdev->devdata;
 	struct devfreq *df = dfc->devfreq;
-	struct devfreq_dev_status *status = &df->last_status;
+	struct devfreq_dev_status status;
 	unsigned long state;
-	unsigned long freq = status->current_frequency;
+	unsigned long freq;
 	unsigned long voltage;
 	u32 dyn_power = 0;
 	u32 static_power = 0;
 	int res;
 
+	mutex_lock(&df->lock);
+	status = df->last_status;
+	mutex_unlock(&df->lock);
+
+	freq = status.current_frequency;
+
 	state = freq_get_state(dfc, freq);
 	if (state == THERMAL_CSTATE_INVALID) {
 		res = -EAGAIN;
@@ -268,16 +287,18 @@ static int devfreq_cooling_get_requested_power(struct thermal_cooling_device *cd
 	} else {
 		dyn_power = dfc->power_table[state];
 
+		_normalize_load(&status);
+
 		/* Scale dynamic power for utilization */
-		dyn_power *= status->busy_time;
-		dyn_power /= status->total_time;
+		dyn_power *= status.busy_time;
+		dyn_power >>= 10;
 		/* Get static power */
 		static_power = get_static_power(dfc, freq);
 
 		*power = dyn_power + static_power;
 	}
 
-	trace_thermal_power_devfreq_get_power(cdev, status, freq, *power);
+	trace_thermal_power_devfreq_get_power(cdev, &status, freq, *power);
 
 	return 0;
 fail:
@@ -309,14 +330,19 @@ static int devfreq_cooling_power2state(struct thermal_cooling_device *cdev,
 {
 	struct devfreq_cooling_device *dfc = cdev->devdata;
 	struct devfreq *df = dfc->devfreq;
-	struct devfreq_dev_status *status = &df->last_status;
-	unsigned long freq = status->current_frequency;
-	unsigned long busy_time;
+	struct devfreq_dev_status status;
+	unsigned long freq;
 	s32 dyn_power;
 	u32 static_power;
 	s32 est_power;
 	int i;
 
+	mutex_lock(&df->lock);
+	status = df->last_status;
+	mutex_unlock(&df->lock);
+
+	freq = status.current_frequency;
+
 	if (dfc->power_ops->get_real_power) {
 		/* Scale for resource utilization */
 		est_power = power * dfc->res_util;
@@ -328,8 +354,9 @@ static int devfreq_cooling_power2state(struct thermal_cooling_device *cdev,
 		dyn_power = dyn_power > 0 ? dyn_power : 0;
 
 		/* Scale dynamic power for utilization */
-		busy_time = status->busy_time ?: 1;
-		est_power = (dyn_power * status->total_time) / busy_time;
+		_normalize_load(&status);
+		dyn_power <<= 10;
+		est_power = dyn_power / status.busy_time;
 	}
 
 	/*
-- 
2.17.1