Re: [PATCH v7 2/9] reboot: thermal: Export hardware protection shutdown

[Daniel Lezcano]

On 14/04/2021 07:52, Matti Vaittinen wrote:
> Thermal core contains a logic for safety shutdown. System is attempted to
> be powered off if temperature exceeds safety limits.
> 
> Currently this can be also utilized by regulator subsystem as a final
> protection measure if PMICs report dangerous over-voltage, over-current or
> over-temperature and if per regulator counter measures fail or do not
> exist.
> 
> Move this logic to kernel/reboot.c and export the functionality for other
> subsystems to use. Also replace the mutex with a spinlock to allow using
> the function from any context.
> 
> Also the EMIF bus code has implemented a safety shut-down. EMIF does not
> attempt orderly_poweroff at all. Thus the EMIF code is not converted to use
> this new function.
> 
> Signed-off-by: Matti Vaittinen <matti.vaittinen@xxxxxxxxxxxxxxxxx>
> ---
> Changelog
>  v7:
>   - new patch
> 
> Please note - this patch has received only a minimal amount of testing.
> (The new API call was tested to shut-down my system at driver probe but
> no odd corner-cases have been tested).
> 
> Any testing for thermal shutdown is appreciated.

You can test it easily by enabling the option CONFIG_THERMAL_EMULATION

Then in any thermal zone:

Assuming the critical temp is below the one specified in the command:

echo 100000 > /sys/class/thermal/thermal_zone0/emul_temp

> ---
>  drivers/thermal/thermal_core.c | 63 ++-----------------------
>  include/linux/reboot.h         |  1 +
>  kernel/reboot.c                | 86 ++++++++++++++++++++++++++++++++++
>  3 files changed, 91 insertions(+), 59 deletions(-)
> 
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 996c038f83a4..b1444845af38 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -36,10 +36,8 @@ static LIST_HEAD(thermal_governor_list);
>  
>  static DEFINE_MUTEX(thermal_list_lock);
>  static DEFINE_MUTEX(thermal_governor_lock);
> -static DEFINE_MUTEX(poweroff_lock);
>  
>  static atomic_t in_suspend;
> -static bool power_off_triggered;
>  
>  static struct thermal_governor *def_governor;
>  
> @@ -327,70 +325,18 @@ static void handle_non_critical_trips(struct thermal_zone_device *tz, int trip)
>  		       def_governor->throttle(tz, trip);
>  }
>  
> -/**
> - * thermal_emergency_poweroff_func - emergency poweroff work after a known delay
> - * @work: work_struct associated with the emergency poweroff function
> - *
> - * This function is called in very critical situations to force
> - * a kernel poweroff after a configurable timeout value.
> - */
> -static void thermal_emergency_poweroff_func(struct work_struct *work)
> -{
> -	/*
> -	 * We have reached here after the emergency thermal shutdown
> -	 * Waiting period has expired. This means orderly_poweroff has
> -	 * not been able to shut off the system for some reason.
> -	 * Try to shut down the system immediately using kernel_power_off
> -	 * if populated
> -	 */
> -	WARN(1, "Attempting kernel_power_off: Temperature too high\n");
> -	kernel_power_off();
> -
> -	/*
> -	 * Worst of the worst case trigger emergency restart
> -	 */
> -	WARN(1, "Attempting emergency_restart: Temperature too high\n");
> -	emergency_restart();
> -}
> -
> -static DECLARE_DELAYED_WORK(thermal_emergency_poweroff_work,
> -			    thermal_emergency_poweroff_func);
> -
> -/**
> - * thermal_emergency_poweroff - Trigger an emergency system poweroff
> - *
> - * This may be called from any critical situation to trigger a system shutdown
> - * after a known period of time. By default this is not scheduled.
> - */
> -static void thermal_emergency_poweroff(void)
> +void thermal_zone_device_critical(struct thermal_zone_device *tz)
>  {
> -	int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS;
>  	/*
>  	 * poweroff_delay_ms must be a carefully profiled positive value.
> -	 * Its a must for thermal_emergency_poweroff_work to be scheduled
> +	 * Its a must for forced_emergency_poweroff_work to be scheduled.
>  	 */
> -	if (poweroff_delay_ms <= 0)
> -		return;
> -	schedule_delayed_work(&thermal_emergency_poweroff_work,
> -			      msecs_to_jiffies(poweroff_delay_ms));
> -}
> +	int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS;
>  
> -void thermal_zone_device_critical(struct thermal_zone_device *tz)
> -{
>  	dev_emerg(&tz->device, "%s: critical temperature reached, "
>  		  "shutting down\n", tz->type);
>  
> -	mutex_lock(&poweroff_lock);
> -	if (!power_off_triggered) {
> -		/*
> -		 * Queue a backup emergency shutdown in the event of
> -		 * orderly_poweroff failure
> -		 */
> -		thermal_emergency_poweroff();
> -		orderly_poweroff(true);
> -		power_off_triggered = true;
> -	}
> -	mutex_unlock(&poweroff_lock);
> +	hw_protection_shutdown("Temperature too high", poweroff_delay_ms);
>  }
>  EXPORT_SYMBOL(thermal_zone_device_critical);
>  
> @@ -1549,7 +1495,6 @@ static int __init thermal_init(void)
>  	ida_destroy(&thermal_cdev_ida);
>  	mutex_destroy(&thermal_list_lock);
>  	mutex_destroy(&thermal_governor_lock);
> -	mutex_destroy(&poweroff_lock);
>  	return result;
>  }
>  postcore_initcall(thermal_init);
> diff --git a/include/linux/reboot.h b/include/linux/reboot.h
> index 3734cd8f38a8..af907a3d68d1 100644
> --- a/include/linux/reboot.h
> +++ b/include/linux/reboot.h
> @@ -79,6 +79,7 @@ extern char poweroff_cmd[POWEROFF_CMD_PATH_LEN];
>  
>  extern void orderly_poweroff(bool force);
>  extern void orderly_reboot(void);
> +void hw_protection_shutdown(const char *reason, int ms_until_forced);
>  
>  /*
>   * Emergency restart, callable from an interrupt handler.
> diff --git a/kernel/reboot.c b/kernel/reboot.c
> index a6ad5eb2fa73..1b5fa6d213d4 100644
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -518,6 +518,92 @@ void orderly_reboot(void)
>  }
>  EXPORT_SYMBOL_GPL(orderly_reboot);
>  
> +/**
> + * hw_failure_emergency_poweroff_func - emergency poweroff work after a known delay
> + * @work: work_struct associated with the emergency poweroff function
> + *
> + * This function is called in very critical situations to force
> + * a kernel poweroff after a configurable timeout value.
> + */
> +static void hw_failure_emergency_poweroff_func(struct work_struct *work)
> +{
> +	/*
> +	 * We have reached here after the emergency shutdown waiting period has
> +	 * expired. This means orderly_poweroff has not been able to shut off
> +	 * the system for some reason.
> +	 *
> +	 * Try to shut down the system immediately using kernel_power_off
> +	 * if populated
> +	 */
> +	WARN(1, "Hardware protection timed-out. Trying forced poweroff\n");
> +	kernel_power_off();
> +
> +	/*
> +	 * Worst of the worst case trigger emergency restart
> +	 */
> +	WARN(1,
> +	     "Hardware protection shutdown failed. Trying emergency restart\n");
> +	emergency_restart();
> +}
> +
> +static DECLARE_DELAYED_WORK(hw_failure_emergency_poweroff_work,
> +			    hw_failure_emergency_poweroff_func);
> +
> +/**
> + * hw_failure_emergency_poweroff - Trigger an emergency system poweroff
> + *
> + * This may be called from any critical situation to trigger a system shutdown
> + * after a given period of time. If time is negative this is not scheduled.
> + */
> +static void hw_failure_emergency_poweroff(int poweroff_delay_ms)
> +{
> +	if (poweroff_delay_ms <= 0)
> +		return;
> +	schedule_delayed_work(&hw_failure_emergency_poweroff_work,
> +			      msecs_to_jiffies(poweroff_delay_ms));
> +}
> +
> +static bool prot_power_off_triggered;
> +static DEFINE_SPINLOCK(poweroff_lock);
> +
> +/**
> + * hw_protection_shutdown - Trigger an emergency system poweroff
> + *
> + * @reason:		Reason of emergency shutdown to be printed.
> + * @ms_until_forced:	Time to wait for orderly shutdown before tiggering a
> + *			forced shudown. Negative value disables the forced
> + *			shutdown.
> + *
> + * Initiate an emergency system shutdown in order to protect hardware from
> + * further damage. Usage examples include a thermal protection or a voltage or
> + * current regulator failures.
> + * NOTE: The request is ignored if protection shutdown is already pending even
> + * if the previous request has given a large timeout for forced shutdown.
> + * Can be called from any context.
> + */
> +void hw_protection_shutdown(const char *reason, int ms_until_forced)
> +{
> +	unsigned long flags;
> +
> +	pr_emerg("HARDWARE PROTECTION shutdown (%s)\n", reason);
> +
> +	spin_lock_irqsave(&poweroff_lock, flags);
> +	if (prot_power_off_triggered) {
> +		spin_unlock(&poweroff_lock);
> +		return;
> +	}
> +	prot_power_off_triggered = true;
> +	spin_unlock_irqrestore(&poweroff_lock, flags);
> +
> +	/*
> +	 * Queue a backup emergency shutdown in the event of
> +	 * orderly_poweroff failure
> +	 */
> +	hw_failure_emergency_poweroff(ms_until_forced);
> +	orderly_poweroff(true);
> +}
> +EXPORT_SYMBOL_GPL(hw_protection_shutdown);
> +
>  static int __init reboot_setup(char *str)
>  {
>  	for (;;) {
> 


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