[PATCH v2] efi: stop hw watchdog during EBS

[Mark Kettenis]

> From: Casey Connolly <casey.connolly at linaro.org>
> Date: Mon, 19 Jan 2026 22:09:25 +0100
> 
> Hardware watchdogs don't currently get stopped as part of
> ExitBootServices, this can result in resets during boot if the OS
> doesn't have a driver for the watchdog, or if the driver isn't loaded
> in time.
> 
> As with the EFI watchdog, stop any hardware watchdogs as well.

This has been discussed before and rejected on the grounds that this
defeats the purpose of the watchdog.  I think there was some consensus
that an OS that doesn't have a driver for the watchdog or doesn't load
it in time is broken.  Some folks also pointed out that on some
platforms it isn't possible to disable the watchdog.

Ultimately, I think EFI needs an API to control the hardware watchdog,
such that an OS doesn't need a driver.

> Signed-off-by: Casey Connolly <casey.connolly at linaro.org>
> ---
> Changes in v2:
> * Fix compilation when CONFIG_WATCHDOG is disabled.
> 
> ---
>  lib/efi_loader/efi_boottime.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> index ddc935d22409..c34616db578a 100644
> --- a/lib/efi_loader/efi_boottime.c
> +++ b/lib/efi_loader/efi_boottime.c
> @@ -21,8 +21,9 @@
>  #include <time.h>
>  #include <u-boot/crc.h>
>  #include <usb.h>
>  #include <watchdog.h>
> +#include <wdt.h>
>  #include <asm/global_data.h>
>  #include <linux/libfdt_env.h>
>  
>  DECLARE_GLOBAL_DATA_PTR;
> @@ -2263,8 +2264,10 @@ static efi_status_t EFIAPI efi_exit_boot_services(efi_handle_t image_handle,
>  	efi_update_table_header_crc32(&systab.hdr);
>  
>  	/* Give the payload some time to boot */
>  	efi_set_watchdog(0);
> +	if (CONFIG_IS_ENABLED(WDT))
> +		wdt_stop_all();
>  	schedule();
>  out:
>  	if (IS_ENABLED(CONFIG_EFI_TCG2_PROTOCOL)) {
>  		if (ret != EFI_SUCCESS)
> -- 
> 2.52.0
> 
>