[PATCH v2] thermal: imx8mm: Allow reboot after critical temperature

[Fabio Estevam]

From: Fabio Estevam <festevam@xxxxxxx>

Currently, after the board reaches the critical temperature, the system
goes through a poweroff mechanism.

In some cases, such behavior does not suit well, as the board may be
unattended in the field and rebooting may be a better approach.

The bootloader may also check the temperature and only allow the boot to
proceed when the temperature is below a certain threshold.

Introduce a reboot_on_critical parameter to indicate that the board
will go through a reboot after the critical temperature is reached.

When this parameter is not selected, the default behavior of forcing a
shutdown is preserved.

Tested on a imx8mm-evk board by passing 'imx8mm_thermal.reboot_on_critical'
via kernel command line.

Signed-off-by: Fabio Estevam <festevam@xxxxxxx>
---
Changes since v1:
- Introduce a module_param() instead of a devicetree property.

 drivers/thermal/imx8mm_thermal.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/thermal/imx8mm_thermal.c b/drivers/thermal/imx8mm_thermal.c
index e89b11b3f2b9..2427bd46ac6c 100644
--- a/drivers/thermal/imx8mm_thermal.c
+++ b/drivers/thermal/imx8mm_thermal.c
@@ -10,9 +10,11 @@
 #include <linux/err.h>
 #include <linux/io.h>
 #include <linux/module.h>
+#include <linux/moduleparam.h>
 #include <linux/nvmem-consumer.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/reboot.h>
 #include <linux/slab.h>
 #include <linux/thermal.h>
 
@@ -75,6 +77,11 @@
 #define TMU_VER1		0x1
 #define TMU_VER2		0x2
 
+static bool reboot_on_critical;
+module_param(reboot_on_critical, bool, 0444);
+MODULE_PARM_DESC(reboot_on_critical,
+		 "Reboot the system after the critical temperature is reached.");
+
 struct thermal_soc_data {
 	u32 num_sensors;
 	u32 version;
@@ -146,8 +153,20 @@ static int tmu_get_temp(struct thermal_zone_device *tz, int *temp)
 	return tmu->socdata->get_temp(sensor, temp);
 }
 
+static void tmu_critical(struct thermal_zone_device *tz)
+{
+	if (reboot_on_critical) {
+		dev_emerg(thermal_zone_device(tz), "%s: critical temperature reached\n",
+			  thermal_zone_device_type(tz));
+		kernel_restart(NULL);
+	} else {
+		thermal_zone_device_critical(tz);
+	}
+}
+
 static const struct thermal_zone_device_ops tmu_tz_ops = {
 	.get_temp = tmu_get_temp,
+	.critical = tmu_critical,
 };
 
 static void imx8mm_tmu_enable(struct imx8mm_tmu *tmu, bool enable)
-- 
2.34.1