Merge tag 'scmi-updates-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into soc/drivers

Arm SCMI updates for v6.4

The main and only new addition this time around is the support for
unidirectional mailbox channels. SCMI communicates between the agent
and the platform using one bidirectional 'a2p' channel used by the agent
to send SCMI commands and synchronously receive the related replies, and
an optional 'p2a' unidirectional channel used to asynchronously receive
delayed responses and notifications emitted from the platform.

In order to support platforms that support only unidirectional mailbox
hardware channels, the existing bindings are extended to support the
same. Both bidirectional and unidirectional channels support for the
SCMI mailbox can coexist. The correct and effective combination of
defined 'mboxes' and 'shmem' descriptors determines the type of the
mailbox channel.

This also contains a fix for the transfers allocation on Rx channel
especially when the base protocol doesn't use Rx channel while some
of the protocols can have dedicated Rx channels.

* tag 'scmi-updates-6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  firmware: arm_scmi: Add support for unidirectional mailbox channels
  dt-bindings: firmware: arm,scmi: Support mailboxes unidirectional channels
  firmware: arm_scmi: Fix xfers allocation on Rx channel
  firmware: arm_scmi: Use the bitmap API to allocate bitmaps
  firmware: arm_scmi: Fix device node validation for mailbox transport
  firmware: arm_scmi: Fix raw coexistence mode behaviour on failure path
  firmware: arm_scmi: Remove duplicate include header inclusion
  firmware: arm_scmi: Return a literal instead of a variable
  firmware: arm_scmi: Clean up a return statement in scmi_probe

Link: https://lore.kernel.org/r/20230417145743.1904318-1-sudeep.holla@arm.com
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 38 insertions, 10 deletions

diff --git a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
index 2f7c51c75e85..5824c43e9893 100644
--- a/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
+++ b/Documentation/devicetree/bindings/firmware/arm,scmi.yaml
@@ -56,17 +56,38 @@ properties:
     description:
       Specifies the mailboxes used to communicate with SCMI compliant
       firmware.
-    items:
-      - const: tx
-      - const: rx
+    oneOf:
+      - items:
+          - const: tx
+          - const: rx
+        minItems: 1
+      - items:
+          - const: tx
+          - const: tx_reply
+          - const: rx
+        minItems: 2
 
   mboxes:
     description:
       List of phandle and mailbox channel specifiers. It should contain
-      exactly one or two mailboxes, one for transmitting messages("tx")
-      and another optional for receiving the notifications("rx") if supported.
+      exactly one, two or three mailboxes; the first one or two for transmitting
+      messages ("tx") and another optional ("rx") for receiving notifications
+      and delayed responses, if supported by the platform.
+      The number of mailboxes needed for transmitting messages depends on the
+      type of channels exposed by the specific underlying mailbox controller;
+      one single channel descriptor is enough if such channel is bidirectional,
+      while two channel descriptors are needed to represent the SCMI ("tx")
+      channel if the underlying mailbox channels are of unidirectional type.
+      The effective combination in numbers of mboxes and shmem descriptors let
+      the SCMI subsystem determine unambiguosly which type of SCMI channels are
+      made available by the underlying mailbox controller and how to use them.
+       1 mbox / 1 shmem => SCMI TX over 1 mailbox bidirectional channel
+       2 mbox / 2 shmem => SCMI TX and RX over 2 mailbox bidirectional channels
+       2 mbox / 1 shmem => SCMI TX over 2 mailbox unidirectional channels
+       3 mbox / 2 shmem => SCMI TX and RX over 3 mailbox unidirectional channels
+      Any other combination of mboxes and shmem is invalid.
     minItems: 1
-    maxItems: 2
+    maxItems: 3
 
   shmem:
     description:
@@ -228,13 +249,20 @@ $defs:
         maxItems: 1
 
       mbox-names:
-        items:
-          - const: tx
-          - const: rx
+        oneOf:
+          - items:
+              - const: tx
+              - const: rx
+            minItems: 1
+          - items:
+              - const: tx
+              - const: tx_reply
+              - const: rx
+            minItems: 2
 
       mboxes:
         minItems: 1
-        maxItems: 2
+        maxItems: 3
 
       shmem:
         minItems: 1