[PATCH] thermal: imx: Fix temperature measurements on i.MX6 after alarm

[Michal Vokáč]

From: Petr Beneš <petr.benes@xxxxxxxxx>

SoC temperature readout may not work after thermal alarm fires interrupt.
This harms userspace as well as CPU cooling device.

Two issues with the logic involved. First, there is no protection against
concurent measurements, hence one can switch the sensor off while
the other one tries to read temperature later. Second, the interrupt path
usually fails. At the end the sensor is powered off and thermal IRQ is
disabled. One has to reenable the thermal zone by the sysfs interface.

Most of troubles come from commit d92ed2c9d3ff ("thermal: imx: Use
driver's local data to decide whether to run a measurement")

It uses data->irq_enabled as the "local data". Indeed, its value is
related to the state of the sensor loosely under normal operation and,
frankly, gets unleashed when the thermal interrupt arrives.

Current patch adds the "local data" (new member sensor_on in
imx_thermal_data) and sets its value in controlled manner.

Fixes: d92ed2c9d3ff ("thermal: imx: Use driver's local data to decide whether to run a measurement")
Cc: petrben@xxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Petr Beneš <petr.benes@xxxxxxxxx>
Signed-off-by: Michal Vokáč <michal.vokac@xxxxxxxxx>
---
 drivers/thermal/imx_thermal.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
index 2c7473d86a59..df5658e21828 100644
--- a/drivers/thermal/imx_thermal.c
+++ b/drivers/thermal/imx_thermal.c
@@ -209,6 +209,8 @@ struct imx_thermal_data {
 	struct clk *thermal_clk;
 	const struct thermal_soc_data *socdata;
 	const char *temp_grade;
+	struct mutex sensor_lock;
+	bool sensor_on;
 };
 
 static void imx_set_panic_temp(struct imx_thermal_data *data,
@@ -252,11 +254,12 @@ static int imx_get_temp(struct thermal_zone_device *tz, int *temp)
 	const struct thermal_soc_data *soc_data = data->socdata;
 	struct regmap *map = data->tempmon;
 	unsigned int n_meas;
-	bool wait, run_measurement;
+	bool wait;
 	u32 val;
 
-	run_measurement = !data->irq_enabled;
-	if (!run_measurement) {
+	mutex_lock(&data->sensor_lock);
+
+	if (data->sensor_on) {
 		/* Check if a measurement is currently in progress */
 		regmap_read(map, soc_data->temp_data, &val);
 		wait = !(val & soc_data->temp_valid_mask);
@@ -283,13 +286,15 @@ static int imx_get_temp(struct thermal_zone_device *tz, int *temp)
 
 	regmap_read(map, soc_data->temp_data, &val);
 
-	if (run_measurement) {
+	if (!data->sensor_on) {
 		regmap_write(map, soc_data->sensor_ctrl + REG_CLR,
 			     soc_data->measure_temp_mask);
 		regmap_write(map, soc_data->sensor_ctrl + REG_SET,
 			     soc_data->power_down_mask);
 	}
 
+	mutex_unlock(&data->sensor_lock);
+
 	if ((val & soc_data->temp_valid_mask) == 0) {
 		dev_dbg(&tz->device, "temp measurement never finished\n");
 		return -EAGAIN;
@@ -339,20 +344,26 @@ static int imx_change_mode(struct thermal_zone_device *tz,
 	const struct thermal_soc_data *soc_data = data->socdata;
 
 	if (mode == THERMAL_DEVICE_ENABLED) {
+		mutex_lock(&data->sensor_lock);
 		regmap_write(map, soc_data->sensor_ctrl + REG_CLR,
 			     soc_data->power_down_mask);
 		regmap_write(map, soc_data->sensor_ctrl + REG_SET,
 			     soc_data->measure_temp_mask);
+		data->sensor_on = true;
+		mutex_unlock(&data->sensor_lock);
 
 		if (!data->irq_enabled) {
 			data->irq_enabled = true;
 			enable_irq(data->irq);
 		}
 	} else {
+		mutex_lock(&data->sensor_lock);
 		regmap_write(map, soc_data->sensor_ctrl + REG_CLR,
 			     soc_data->measure_temp_mask);
 		regmap_write(map, soc_data->sensor_ctrl + REG_SET,
 			     soc_data->power_down_mask);
+		data->sensor_on = false;
+		mutex_unlock(&data->sensor_lock);
 
 		if (data->irq_enabled) {
 			disable_irq(data->irq);
@@ -728,6 +739,8 @@ static int imx_thermal_probe(struct platform_device *pdev)
 	}
 
 	/* Make sure sensor is in known good state for measurements */
+	mutex_init(&data->sensor_lock);
+	mutex_lock(&data->sensor_lock);
 	regmap_write(map, data->socdata->sensor_ctrl + REG_CLR,
 		     data->socdata->power_down_mask);
 	regmap_write(map, data->socdata->sensor_ctrl + REG_CLR,
@@ -739,6 +752,8 @@ static int imx_thermal_probe(struct platform_device *pdev)
 			IMX6_MISC0_REFTOP_SELBIASOFF);
 	regmap_write(map, data->socdata->sensor_ctrl + REG_SET,
 		     data->socdata->power_down_mask);
+	data->sensor_on = false;
+	mutex_unlock(&data->sensor_lock);
 
 	ret = imx_thermal_register_legacy_cooling(data);
 	if (ret)
@@ -796,10 +811,13 @@ static int imx_thermal_probe(struct platform_device *pdev)
 	if (data->socdata->version == TEMPMON_IMX6SX)
 		imx_set_panic_temp(data, data->temp_critical);
 
+	mutex_lock(&data->sensor_lock);
 	regmap_write(map, data->socdata->sensor_ctrl + REG_CLR,
 		     data->socdata->power_down_mask);
 	regmap_write(map, data->socdata->sensor_ctrl + REG_SET,
 		     data->socdata->measure_temp_mask);
+	data->sensor_on = true;
+	mutex_unlock(&data->sensor_lock);
 
 	data->irq_enabled = true;
 	ret = thermal_zone_device_enable(data->tz);
@@ -832,8 +850,12 @@ static int imx_thermal_remove(struct platform_device *pdev)
 	struct regmap *map = data->tempmon;
 
 	/* Disable measurements */
+	mutex_lock(&data->sensor_lock);
 	regmap_write(map, data->socdata->sensor_ctrl + REG_SET,
 		     data->socdata->power_down_mask);
+	data->sensor_on = false;
+	mutex_unlock(&data->sensor_lock);
+
 	if (!IS_ERR(data->thermal_clk))
 		clk_disable_unprepare(data->thermal_clk);
 
-- 
2.25.1