[PATCH v2 1/2] dt-bindings: firmware: arm,scmi: Document arm,poll-transport property

[Marek Vasut]

Document new property arm,poll-transport, which sets all SCMI operation into
poll mode. This is meant to work around uncooperative SCP implementations,
which do not generate completion interrupts. This applies primarily on mbox
shmem based implementations.

With this property set, such implementations which do not generate interrupts
can be interacted with, until they are fixed to generate interrupts properly.

Note that, because the original base protocol exchange also requires some
sort of completion mechanism, it is not possible to query SCMI itself for
this property and it must be described in DT. While this does look a bit
like policy, the SCMI provider is part of the hardware, hence DT.

Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Cc: Conor Dooley <conor+dt at kernel.org>
Cc: Cristian Marussi <cristian.marussi at arm.com>
Cc: Florian Fainelli <florian.fainelli at broadcom.com>
Cc: Krzysztof Kozlowski <krzk+dt at kernel.org>
Cc: Rob Herring <robh at kernel.org>
Cc: Sudeep Holla <sudeep.holla at arm.com>
Cc: arm-scmi at vger.kernel.org
Cc: devicetree at vger.kernel.org
Cc: linux-arm-kernel at lists.infradead.org
Cc: linux-renesas-soc at vger.kernel.org
---
V2: s at mean@&t and limit poll transport to mailbox/shmem only
---
 .../devicetree/bindings/firmware/arm,scmi.yaml         | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
index be817fd9cc34b..f4bf4173c5c7e 100644
--- a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
+++ b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
@@ -146,6 +146,13 @@ properties:
       this platform. If set, the value should be non-zero.
     minimum: 1
 
+  arm,poll-transport:
+    type: boolean
+    description:
+      An optional property which unconditionally forces polling in all transports.
+      This is mainly meant to work around uncooperative SCP, which does not generate
+      completion interrupts.
+
   arm,smc-id:
     $ref: /schemas/types.yaml#/definitions/uint32
     description:
@@ -379,6 +386,9 @@ then:
     - shmem
 
 else:
+  properties:
+    arm,poll-transport: false
+
   if:
     properties:
       compatible:
-- 
2.51.0