[PATCH v8 2/3] dt-bindings: mmc: Add reset-card-at-resume property

[Kamal Dasu <kamal.dasu@broadcom.com>]

On some platforms, firmware or other hardware accesses the card
during suspend/resume, before the kernel's own resume path has run,
leaving the card in a state the kernel can no longer assume it knows.
Add a flag property so such boards can tell the mmc core the card
needs to be reset before it can be used again.

This is expected to be paired with keep-power-in-suspend on boards
whose firmware needs the card to stay powered and live throughout
suspend: since the card is never power-cycled, nothing else would
force it back to a known state on resume.

Signed-off-by: Kamal Dasu <kamal.dasu@broadcom.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
---
Changes in v8:
  - Sashiko's AI review of v7 pointed out this property's own
    description says it's "expected to be paired with
    keep-power-in-suspend", and patch 3/3 now enforces exactly that
    pairing in the driver, but nothing enforced it in the schema --
    a DT could set reset-card-at-resume alone and still pass
    dt_binding_check. Rob Herring asked for this to be addressed on
    the list. Added a dependencies entry requiring
    keep-power-in-suspend whenever reset-card-at-resume is present.

Changes in v7:
  - No other change here; patch 3/3 now requires this property
    alongside keep-power-in-suspend for (e)MMC rather than treating
    them as fully independent in the driver -- see that patch's
    changelog.

Changes in v6:
  - New patch, per Ulf's suggestion: rather than fold "needs a reset
    at resume" into keep-power-in-suspend's own meaning, describe it
    as its own independent property, so the two can be combined only
    where actually needed (brcmstb sets both; SDIO's existing
    keep-power-in-suspend users are unaffected and set neither this
    nor a reset).

 Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
index c18bf0d6a56e..c51e9184384d 100644
--- a/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
+++ b/Documentation/devicetree/bindings/mmc/mmc-controller-common.yaml
@@ -293,6 +293,13 @@ properties:
     description:
       Preserves card power during a suspend/resume cycle.
 
+  reset-card-at-resume:
+    $ref: /schemas/types.yaml#/definitions/flag
+    description:
+      The HW/FW may have accessed the card during suspend/resume,
+      leaving it in an unknown state. Hence, before the card can be
+      used, it must be reset.
+
   wakeup-source:
     $ref: /schemas/types.yaml#/definitions/flag
     description:
@@ -361,5 +368,6 @@ patternProperties:
 dependencies:
   cd-debounce-delay-ms: [ cd-gpios ]
   fixed-emmc-driver-type: [ non-removable ]
+  reset-card-at-resume: [ keep-power-in-suspend ]
 
 additionalProperties: true
-- 
2.34.1