linux-kernel - [PATCH v2 2/5] thermal: devfreq_cooling: get a copy of device status

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Message-Id: <20201118120358.17150-3-lukasz.luba@arm.com>
Date:   Wed, 18 Nov 2020 12:03:55 +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 v2 2/5] thermal: devfreq_cooling: get a copy of device status

Devfreq cooling needs to now the correct status of the device in order
to operate. Do not rely on Devfreq last_status which might be a stale data
and get more up-to-date values of the load.

Devfreq framework can change the device status in the background. To
mitigate this situation 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, it is in a sane range.

Signed-off-by: Lukasz Luba <lukasz.luba@....com>
---
 drivers/thermal/devfreq_cooling.c | 52 +++++++++++++++++++++++++------
 1 file changed, 43 insertions(+), 9 deletions(-)

diff --git a/drivers/thermal/devfreq_cooling.c b/drivers/thermal/devfreq_cooling.c
index 659c0143c9f0..925523694462 100644
--- a/drivers/thermal/devfreq_cooling.c
+++ b/drivers/thermal/devfreq_cooling.c
@@ -227,20 +227,46 @@ static inline unsigned long get_total_power(struct devfreq_cooling_device *dfc,
 							       voltage);
 }
 
+static void _normalize_load(struct devfreq_dev_status *status)
+{
+	/* Make some space if needed */
+	if (status->busy_time > 0xffff) {
+		status->busy_time >>= 10;
+		status->total_time >>= 10;
+	}
+
+	if (status->busy_time > status->total_time)
+		status->busy_time = status->total_time;
+
+	status->busy_time *= 100;
+	status->busy_time /= status->total_time ? : 1;
+
+	/* Avoid division by 0 */
+	status->busy_time = status->busy_time ? : 1;
+	status->total_time = 100;
+}
 
 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);
+	res = df->profile->get_dev_status(df->dev.parent, &status);
+	mutex_unlock(&df->lock);
+	if (res)
+		return res;
+
+	freq = status.current_frequency;
+
 	state = freq_get_state(dfc, freq);
 	if (state == THERMAL_CSTATE_INVALID) {
 		res = -EAGAIN;
@@ -268,16 +294,18 @@ 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 /= status.total_time;
 		/* 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 +337,20 @@ 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;
+	struct devfreq_dev_status status;
 	unsigned long busy_time;
+	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 +362,8 @@ 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;
+		busy_time = status.busy_time ?: 1;
+		est_power = (dyn_power * status.total_time) / busy_time;
 	}
 
 	/*
-- 
2.17.1