[PATCH 2/2] thermal: imx: implement thermal alarm interrupt handling

[Philipp Zabel <p.zabel@pengutronix.de>]

Enable automatic measurements at 10 Hz and use the alarm interrupt to react
more quickly to sudden temperature changes above the passive or critical
temperature trip points.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 drivers/thermal/imx_thermal.c | 140 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 127 insertions(+), 13 deletions(-)

diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
index 9387e47..411be0a 100644
--- a/drivers/thermal/imx_thermal.c
+++ b/drivers/thermal/imx_thermal.c
@@ -12,6 +12,7 @@
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/init.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/mfd/syscon.h>
@@ -31,6 +32,8 @@
 #define MISC0_REFTOP_SELBIASOFF		(1 << 3)
 
 #define TEMPSENSE0			0x0180
+#define TEMPSENSE0_ALARM_VALUE_SHIFT	20
+#define TEMPSENSE0_ALARM_VALUE_MASK	(0xfff << TEMPSENSE0_ALARM_VALUE_SHIFT)
 #define TEMPSENSE0_TEMP_CNT_SHIFT	8
 #define TEMPSENSE0_TEMP_CNT_MASK	(0xfff << TEMPSENSE0_TEMP_CNT_SHIFT)
 #define TEMPSENSE0_FINISHED		(1 << 2)
@@ -66,33 +69,62 @@ struct imx_thermal_data {
 	int c1, c2; /* See formula in imx_get_sensor_data() */
 	unsigned long temp_passive;
 	unsigned long temp_critical;
+	unsigned long alarm_temp;
+	unsigned long last_temp;
+	bool irq_enabled;
+	int irq;
 };
 
+static void imx_set_alarm_temp(struct imx_thermal_data *data,
+			       signed long alarm_temp)
+{
+	struct regmap *map = data->tempmon;
+	int alarm_value;
+
+	data->alarm_temp = alarm_temp;
+	alarm_value = (alarm_temp - data->c2) / data->c1;
+	regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_ALARM_VALUE_MASK);
+	regmap_write(map, TEMPSENSE0 + REG_SET, alarm_value <<
+			TEMPSENSE0_ALARM_VALUE_SHIFT);
+}
+
 static int imx_get_temp(struct thermal_zone_device *tz, unsigned long *temp)
 {
 	struct imx_thermal_data *data = tz->devdata;
 	struct regmap *map = data->tempmon;
-	static unsigned long last_temp;
 	unsigned int n_meas;
+	bool wait;
 	u32 val;
 
-	/*
-	 * Every time we measure the temperature, we will power on the
-	 * temperature sensor, enable measurements, take a reading,
-	 * disable measurements, power off the temperature sensor.
-	 */
-	regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_POWER_DOWN);
-	regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_MEASURE_TEMP);
+	if (data->mode == THERMAL_DEVICE_ENABLED) {
+		/* Check if a measurement is currently in progress */
+		regmap_read(map, TEMPSENSE0, &val);
+		wait = !(val & TEMPSENSE0_FINISHED);
+	} else {
+		/*
+		 * Every time we measure the temperature, we will power on the
+		 * temperature sensor, enable measurements, take a reading,
+		 * disable measurements, power off the temperature sensor.
+		 */
+		regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_POWER_DOWN);
+		regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_MEASURE_TEMP);
+
+		wait = true;
+	}
 
 	/*
 	 * According to the temp sensor designers, it may require up to ~17us
 	 * to complete a measurement.
 	 */
-	usleep_range(20, 50);
+	if (wait)
+		usleep_range(20, 50);
 
 	regmap_read(map, TEMPSENSE0, &val);
-	regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_MEASURE_TEMP);
-	regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_POWER_DOWN);
+
+	if (data->mode != THERMAL_DEVICE_ENABLED) {
+		regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_MEASURE_TEMP);
+		regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_POWER_DOWN);
+	}
 
 	if ((val & TEMPSENSE0_FINISHED) == 0) {
 		dev_dbg(&tz->device, "temp measurement never finished\n");
@@ -104,9 +136,24 @@ static int imx_get_temp(struct thermal_zone_device *tz, unsigned long *temp)
 	/* See imx_get_sensor_data() for formula derivation */
 	*temp = data->c2 + data->c1 * n_meas;
 
-	if (*temp != last_temp) {
+	/* Update alarm value to next higher trip point */
+	if (data->alarm_temp == data->temp_passive && *temp >= data->temp_passive)
+		imx_set_alarm_temp(data, data->temp_critical);
+	if (data->alarm_temp == data->temp_critical && *temp < data->temp_passive) {
+		imx_set_alarm_temp(data, data->temp_passive);
+		dev_dbg(&tz->device, "thermal alarm off: T < %lu\n",
+			data->alarm_temp / 1000);
+	}
+
+	if (*temp != data->last_temp) {
 		dev_dbg(&tz->device, "millicelsius: %ld\n", *temp);
-		last_temp = *temp;
+		data->last_temp = *temp;
+	}
+
+	/* Reenable alarm IRQ if temperature below alarm temperature */
+	if (!data->irq_enabled && *temp < data->alarm_temp) {
+		data->irq_enabled = true;
+		enable_irq(data->irq);
 	}
 
 	return 0;
@@ -126,13 +173,30 @@ static int imx_set_mode(struct thermal_zone_device *tz,
 			enum thermal_device_mode mode)
 {
 	struct imx_thermal_data *data = tz->devdata;
+	struct regmap *map = data->tempmon;
 
 	if (mode == THERMAL_DEVICE_ENABLED) {
 		tz->polling_delay = IMX_POLLING_DELAY;
 		tz->passive_delay = IMX_PASSIVE_DELAY;
+
+		regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_POWER_DOWN);
+		regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_MEASURE_TEMP);
+
+		if (!data->irq_enabled) {
+			data->irq_enabled = true;
+			enable_irq(data->irq);
+		}
 	} else {
+		regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_MEASURE_TEMP);
+		regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_POWER_DOWN);
+
 		tz->polling_delay = 0;
 		tz->passive_delay = 0;
+
+		if (data->irq_enabled) {
+			disable_irq(data->irq);
+			data->irq_enabled = false;
+		}
 	}
 
 	data->mode = mode;
@@ -181,6 +245,8 @@ static int imx_set_trip_temp(struct thermal_zone_device *tz, int trip,
 
 	data->temp_passive = temp;
 
+	imx_set_alarm_temp(data, temp);
+
 	return 0;
 }
 
@@ -299,11 +365,34 @@ static int imx_get_sensor_data(struct platform_device *pdev)
 	return 0;
 }
 
+static irqreturn_t imx_thermal_alarm_irq(int irq, void *dev)
+{
+	struct imx_thermal_data *data = dev;
+
+	disable_irq_nosync(irq);
+	data->irq_enabled = false;
+
+	return IRQ_WAKE_THREAD;
+}
+
+static irqreturn_t imx_thermal_alarm_irq_thread(int irq, void *dev)
+{
+	struct imx_thermal_data *data = dev;
+
+	dev_dbg(&data->tz->device, "THERMAL ALARM: T > %lu\n",
+		data->alarm_temp / 1000);
+
+	thermal_zone_device_update(data->tz);
+
+	return IRQ_HANDLED;
+}
+
 static int imx_thermal_probe(struct platform_device *pdev)
 {
 	struct imx_thermal_data *data;
 	struct cpumask clip_cpus;
 	struct regmap *map;
+	int measure_freq;
 	int ret;
 
 	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
@@ -318,6 +407,18 @@ static int imx_thermal_probe(struct platform_device *pdev)
 	}
 	data->tempmon = map;
 
+	data->irq = platform_get_irq(pdev, 0);
+	if (data->irq < 0)
+		return data->irq;
+
+	ret = devm_request_threaded_irq(&pdev->dev, data->irq,
+			imx_thermal_alarm_irq, imx_thermal_alarm_irq_thread,
+			0, "imx_thermal", data);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to request alarm irq: %d\n", ret);
+		return ret;
+	}
+
 	platform_set_drvdata(pdev, data);
 
 	ret = imx_get_sensor_data(pdev);
@@ -356,6 +457,15 @@ static int imx_thermal_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	/* Enable measurements at ~ 10 Hz */
+	regmap_write(map, TEMPSENSE1 + REG_CLR, TEMPSENSE1_MEASURE_FREQ);
+	measure_freq = DIV_ROUND_UP(32768, 10); /* 10 Hz */
+	regmap_write(map, TEMPSENSE1 + REG_SET, measure_freq);
+	imx_set_alarm_temp(data, data->temp_passive);
+	regmap_write(map, TEMPSENSE0 + REG_CLR, TEMPSENSE0_POWER_DOWN);
+	regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_MEASURE_TEMP);
+
+	data->irq_enabled = true;
 	data->mode = THERMAL_DEVICE_ENABLED;
 
 	return 0;
@@ -364,6 +474,10 @@ static int imx_thermal_probe(struct platform_device *pdev)
 static int imx_thermal_remove(struct platform_device *pdev)
 {
 	struct imx_thermal_data *data = platform_get_drvdata(pdev);
+	struct regmap *map = data->tempmon;
+
+	/* Disable measurements */
+	regmap_write(map, TEMPSENSE0 + REG_SET, TEMPSENSE0_POWER_DOWN);
 
 	thermal_zone_device_unregister(data->tz);
 	cpufreq_cooling_unregister(data->cdev);
-- 
1.8.4.rc0