Re: [PATCH] leds: handle suspend/resume in heartbeat trigger

[Jacek Anaszewski <j.anaszewski@samsung.com>]

Hi Linus,

Thanks for the patch, applied.

Best regards,
Jacek Anaszewski

On 06/02/2016 03:41 PM, Linus Walleij wrote:
> The following phenomena was observed: when suspending the
> system, sometimes the heartbeat LED was left on, glowing and
> wasting power while the rest of the system is asleep, also
> disturbing power dissapation measures on the odd suspend
> cycle when it's left on.
>
> Clearly this is not how we want the heartbeat trigger to
> work: it should turn off and leave the LED off during
> system suspend.
>
> This removes the heartbeat trigger when preparing suspend and
> restores it during resume. The trigger code will make sure all
> LEDs are left in OFF state after removing the trigger, and
> will re-enable the trigger on all LEDs after resuming.
>
> Cc: linux-pm@vger.kernel.org
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
>   drivers/leds/trigger/ledtrig-heartbeat.c | 27 +++++++++++++++++++++++++++
>   1 file changed, 27 insertions(+)
>
> diff --git a/drivers/leds/trigger/ledtrig-heartbeat.c b/drivers/leds/trigger/ledtrig-heartbeat.c
> index 410c39c62dc7..c80e91152b6b 100644
> --- a/drivers/leds/trigger/ledtrig-heartbeat.c
> +++ b/drivers/leds/trigger/ledtrig-heartbeat.c
> @@ -19,6 +19,7 @@
>   #include <linux/sched.h>
>   #include <linux/leds.h>
>   #include <linux/reboot.h>
> +#include <linux/suspend.h>
>   #include "../leds.h"
>
>   static int panic_heartbeats;
> @@ -154,6 +155,26 @@ static struct led_trigger heartbeat_led_trigger = {
>   	.deactivate = heartbeat_trig_deactivate,
>   };
>
> +static int heartbeat_pm_notifier(struct notifier_block *nb,
> +				 unsigned long pm_event, void *unused)
> +{
> +	int rc;
> +
> +	switch (pm_event) {
> +	case PM_SUSPEND_PREPARE:
> +		led_trigger_unregister(&heartbeat_led_trigger);
> +		break;
> +	case PM_POST_SUSPEND:
> +		rc = led_trigger_register(&heartbeat_led_trigger);
> +		if (rc)
> +			pr_err("could not re-register heartbeat trigger\n");
> +		break;
> +	default:
> +		break;
> +	}
> +	return NOTIFY_DONE;
> +}
> +
>   static int heartbeat_reboot_notifier(struct notifier_block *nb,
>   				     unsigned long code, void *unused)
>   {
> @@ -168,6 +189,10 @@ static int heartbeat_panic_notifier(struct notifier_block *nb,
>   	return NOTIFY_DONE;
>   }
>
> +static struct notifier_block heartbeat_pm_nb = {
> +	.notifier_call = heartbeat_pm_notifier,
> +};
> +
>   static struct notifier_block heartbeat_reboot_nb = {
>   	.notifier_call = heartbeat_reboot_notifier,
>   };
> @@ -184,12 +209,14 @@ static int __init heartbeat_trig_init(void)
>   		atomic_notifier_chain_register(&panic_notifier_list,
>   					       &heartbeat_panic_nb);
>   		register_reboot_notifier(&heartbeat_reboot_nb);
> +		register_pm_notifier(&heartbeat_pm_nb);
>   	}
>   	return rc;
>   }
>
>   static void __exit heartbeat_trig_exit(void)
>   {
> +	unregister_pm_notifier(&heartbeat_pm_nb);
>   	unregister_reboot_notifier(&heartbeat_reboot_nb);
>   	atomic_notifier_chain_unregister(&panic_notifier_list,
>   					 &heartbeat_panic_nb);
>