Re: [PATCH] PM: sleep: Allow disabling DPM watchdog by default

[Rafael J. Wysocki]

On Thu, May 28, 2026 at 12:32 PM Tzung-Bi Shih <tzungbi@xxxxxxxxxx> wrote:
>
> Introduce the CONFIG_DPM_WATCHDOG_DEFAULT_ENABLED Kconfig option to
> allow the device suspend/resume watchdog (DPM watchdog) to be disabled
> by default at compile time.
>
> Additionally, introduce the "dpm_watchdog_enabled" boot parameter to
> enable or disable the watchdog at boot time.
>
> This provides flexibility for systems that want the watchdog code
> compiled in but inactive by default, allowing it to be enabled only when
> needed.
>
> Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>
> ---
>  .../admin-guide/kernel-parameters.txt         |  8 ++++++++
>  drivers/base/power/main.c                     | 20 +++++++++++++++++++
>  kernel/power/Kconfig                          |  9 +++++++++
>  3 files changed, 37 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 85936e48cf9a..3a919e660137 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1344,6 +1344,14 @@ Kernel parameters
>                         it becomes active and is searched during signature
>                         verification.
>
> +       dpm_watchdog_enabled=
> +                       [KNL] Enable or disable the device suspend/resume
> +                       watchdog (DPM watchdog).
> +                       Format: {"0" | "1"}
> +                       0: disable
> +                       1: enable
> +                       Default value is set by CONFIG_DPM_WATCHDOG_DEFAULT_ENABLED.
> +
>         driver_async_probe=  [KNL]
>                         List of driver names to be probed asynchronously. *
>                         matches with all driver names. If * is specified, the
> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
> index e1b550664bab..4f92905f3edf 100644
> --- a/drivers/base/power/main.c
> +++ b/drivers/base/power/main.c
> @@ -527,6 +527,20 @@ module_param(dpm_watchdog_all_cpu_backtrace, bool, 0644);
>  MODULE_PARM_DESC(dpm_watchdog_all_cpu_backtrace,
>                  "Backtrace all CPUs on DPM watchdog timeout");
>
> +#ifdef CONFIG_DPM_WATCHDOG_DEFAULT_ENABLED
> +static unsigned int __read_mostly dpm_watchdog_enabled = 1;
> +#else
> +static unsigned int __read_mostly dpm_watchdog_enabled;
> +#endif
> +
> +static int __init dpm_watchdog_setup(char *str)
> +{
> +       if (kstrtouint(str, 0, &dpm_watchdog_enabled) == 0)
> +               return 1;
> +       return 0;
> +}
> +__setup("dpm_watchdog_enabled=", dpm_watchdog_setup);

You might as well use a module parameter to allow this to be set or
clear at run time.  Is there a particular reason why you only want it
to be enabled or disabled via the kernel command line?

> +
>  /**
>   * dpm_watchdog_handler - Driver suspend / resume watchdog handler.
>   * @t: The timer that PM watchdog depends on.
> @@ -570,6 +584,9 @@ static void dpm_watchdog_set(struct dpm_watchdog *wd, struct device *dev)
>  {
>         struct timer_list *timer = &wd->timer;
>
> +       if (!dpm_watchdog_enabled)
> +               return;
> +
>         wd->dev = dev;
>         wd->tsk = current;
>         wd->fatal = CONFIG_DPM_WATCHDOG_TIMEOUT == CONFIG_DPM_WATCHDOG_WARNING_TIMEOUT;
> @@ -588,6 +605,9 @@ static void dpm_watchdog_clear(struct dpm_watchdog *wd)
>  {
>         struct timer_list *timer = &wd->timer;
>
> +       if (!dpm_watchdog_enabled)
> +               return;
> +
>         timer_delete_sync(timer);
>         timer_destroy_on_stack(timer);
>  }
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 05337f437cca..d4cecdb8575e 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -267,6 +267,15 @@ config DPM_WATCHDOG
>           captured in pstore device for inspection in subsequent
>           boot session.
>
> +config DPM_WATCHDOG_DEFAULT_ENABLED
> +       bool "Enable DPM watchdog by default"
> +       depends on DPM_WATCHDOG
> +       default y
> +       help
> +         If you say Y here, the DPM watchdog will be enabled by default.
> +         If you say N, it will be compiled in but disabled, requiring a
> +         boot parameter to activate.
> +
>  config DPM_WATCHDOG_TIMEOUT
>         int "Watchdog timeout to panic in seconds"
>         range 1 120
> --
> 2.54.0.929.g9b7fa37559-goog
>