Add description clarifying that for Versal IPI mailboxes, both host and
remote agents must have the "msg" register region defined for successful
message passing. Without both, only notification-based communication
works.

Signed-off-by: Harini T <harini.t@amd.com>
---
 .../bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml           | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
index 04d6473d666f..8fdf77c7935c 100644
--- a/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
+++ b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
@@ -165,6 +165,12 @@ allOf:
         reg-names: false
 
     else:
+      description:
+        For Versal IPI mailboxes, the "msg" register region is optional.
+        However, for successful message passing via mailbox, both the host IPI
+        agent and the remote IPI agent must have the "msg" register region
+        defined. If either agent lacks the "msg" field, only notification-based
+        communication (without message buffers) will work.
       properties:
         reg:
           items:
-- 
2.43.0

On Mon, Dec 22, 2025 at 10:16:53AM +0530, Harini T wrote:
> Add description clarifying that for Versal IPI mailboxes, both host and
> remote agents must have the "msg" register region defined for successful
> message passing. Without both, only notification-based communication
> works.
> 
> Signed-off-by: Harini T <harini.t@amd.com>
> ---
>  .../bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml           | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
> index 04d6473d666f..8fdf77c7935c 100644
> --- a/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
> +++ b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
> @@ -165,6 +165,12 @@ allOf:
>          reg-names: false
>  
>      else:
> +      description:

Else block cannot have description.

> +        For Versal IPI mailboxes, the "msg" register region is optional.

So it is optional...

> +        However, for successful message passing via mailbox, both the host IPI

And it is not optional. If nothing works, then it is not optional.

And why would it be optional in the first place? You generate your same
IP with different settings?

Best regards,
Krzysztof