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

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)
  pmic       - PMIC-initiated reset

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