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

[Daniel Lezcano <daniel.lezcano@linaro.org>]

Hi Fabio,

On 24/08/2023 13:27, Fabio Estevam wrote:
> From: Fabio Estevam <festevam@denx.de>
> 
> 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@denx.de>
> ---
> 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);
> +	}
> +}

Is it possible to set the .critical ops at init time instead and get rid 
of the thermal_zone_device_critical(tz) call ?

>   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)

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