Re: [PATCH] schemas: chosen: Add reset-reason property

Hi,

On Tue, 26 May 2026 at 04:40, A. Sverdlin
<[email protected]> wrote:
>
> From: Alexander Sverdlin <[email protected]>
>
> Bootloaders such as U-Boot and barebox can populate the /chosen node with
> a reset-reason string property indicating the cause of the most recent
> system reset.
>
> Define a standardized set of generic reset reason values that bootloaders
> map their platform-specific reset sources to:
>
>   unknown    - reset source could not be determined
>   cold       - power-on reset
>   warm       - warm restart without full power cycle
>   watchdog   - watchdog timer expiration
>   wakeup     - wake from suspend/sleep
>   jtag       - JTAG/debug initiated reset
>   thermal    - thermal shutdown/overtemperature
>   external   - external reset pin/signal
>   brownout   - supply voltage drop
>   software   - explicit software-initiated reset
>   safety     - hardware fault detection (e.g. error signaling module,
>                fault collection and control unit)
>   security   - security subsystem (e.g. secure enclave violation)

These all seem fine to me

>   pmic       - PMIC-initiated reset

pmic seems more like a means than a reason. Could you give an example
of when this might be used, rather than the other reasons?

>
> Mapping of platform-specific reset sources to generic values:
>
>   Generic      AM6x              i.MX9            barebox
>   -------      ----              -----            -------
>   unknown      UNKNOWN           -                unknown
>   cold         POR               por              POR
>   warm         RST (SW warm)     -                RST
>   watchdog     WDOG              wdog             WDG
>   wakeup       -                 -                WKE
>   jtag         JTAG              jtag             JTAG
>   thermal      THERMAL           tempsense        THERM
>   external     PIN               -                EXT
>   brownout     -                 -                BROWNOUT
>   software     -                 sw               -
>   safety       ESM               fccu             -
>   security     -                 ele              -
>   pmic         -                 pmic             -
>
> Note: barebox already populates this property but uses abbreviated
> uppercase values (common/reset_source.c). These will need to be adapted
> to match the standardized lowercase values defined here.
>
> The list can be extended in the future as needed.
>
> Link: https://lore.kernel.org/all/[email protected]/
> Signed-off-by: Alexander Sverdlin <[email protected]>
> ---
> Krzk, apparently /chosen is already potentially very dynamic, thanks to
> kaslr-seed and rng-seed properties.
>
>  dtschema/schemas/chosen.yaml | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
>
> diff --git a/dtschema/schemas/chosen.yaml b/dtschema/schemas/chosen.yaml
> index 63f3c12..2daf791 100644
> --- a/dtschema/schemas/chosen.yaml
> +++ b/dtschema/schemas/chosen.yaml
> @@ -183,6 +183,33 @@ properties:
>        will assign devices in its usual manner, otherwise it will not try to
>        assign devices and instead use them as they are configured already.
>
> +  reset-reason:
> +    $ref: types.yaml#/definitions/string
> +    enum:
> +      - unknown
> +      - cold
> +      - warm
> +      - watchdog
> +      - wakeup
> +      - jtag
> +      - thermal
> +      - external
> +      - brownout
> +      - software
> +      - safety
> +      - security
> +      - pmic
> +    description:
> +      This property is set by the bootloader to indicate the reason for the
> +      most recent system reset. The values are generic categories that
> +      bootloaders map their platform-specific reset sources to.

The meaning of each item should really be in the schema, IMO

> +
> +      / {
> +              chosen {
> +                      reset-reason = "watchdog";
> +              };
> +      };
> +
>    smbios3-entrypoint:
>      $ref: types.yaml#/definitions/address
>      maxItems: 1
> --
> 2.52.0
>

Regards,
Simon