Merge tag 'optee-async-notif-for-v5.17' of https://git.linaro.org/people/jens.wiklander/linux-tee into arm/drivers

OP-TEE Asynchronous notifications from secure world

Adds support in the SMC based OP-TEE driver to receive asynchronous
notifications from secure world using an edge-triggered interrupt as
delivery mechanism.

* tag 'optee-async-notif-for-v5.17' of https://git.linaro.org/people/jens.wiklander/linux-tee:
  optee: Fix NULL but dereferenced coccicheck error
  optee: add asynchronous notifications
  optee: separate notification functions
  tee: export teedev_open() and teedev_close_context()
  tee: fix put order in teedev_close_context()
  dt-bindings: arm: optee: add interrupt property
  docs: staging/tee.rst: add a section on OP-TEE notifications

Link: https://lore.kernel.org/r/20211213102359.GA1638682@jade
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

2 files changed, 38 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.yaml b/Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.yaml
index c24047c1fdd5..9a426110a14a 100644
--- a/Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.yaml
+++ b/Documentation/devicetree/bindings/arm/firmware/linaro,optee-tz.yaml
@@ -24,6 +24,12 @@ properties:
   compatible:
     const: linaro,optee-tz
 
+  interrupts:
+    maxItems: 1
+    description: |
+      This interrupt which is used to signal an event by the secure world
+      software is expected to be edge-triggered.
+
   method:
     enum: [smc, hvc]
     description: |
@@ -42,10 +48,12 @@ additionalProperties: false
 
 examples:
   - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
     firmware  {
         optee  {
             compatible = "linaro,optee-tz";
             method = "smc";
+            interrupts = <GIC_SPI 187 IRQ_TYPE_EDGE_RISING>;
         };
     };
 
diff --git a/Documentation/staging/tee.rst b/Documentation/staging/tee.rst
index 4d4b5f889603..3c63d8dcd61e 100644
--- a/Documentation/staging/tee.rst
+++ b/Documentation/staging/tee.rst
@@ -184,6 +184,36 @@ order to support device enumeration. In other words, OP-TEE driver invokes this
 application to retrieve a list of Trusted Applications which can be registered
 as devices on the TEE bus.
 
+OP-TEE notifications
+--------------------
+
+There are two kinds of notifications that secure world can use to make
+normal world aware of some event.
+
+1. Synchronous notifications delivered with ``OPTEE_RPC_CMD_NOTIFICATION``
+   using the ``OPTEE_RPC_NOTIFICATION_SEND`` parameter.
+2. Asynchronous notifications delivered with a combination of a non-secure
+   edge-triggered interrupt and a fast call from the non-secure interrupt
+   handler.
+
+Synchronous notifications are limited by depending on RPC for delivery,
+this is only usable when secure world is entered with a yielding call via
+``OPTEE_SMC_CALL_WITH_ARG``. This excludes such notifications from secure
+world interrupt handlers.
+
+An asynchronous notification is delivered via a non-secure edge-triggered
+interrupt to an interrupt handler registered in the OP-TEE driver. The
+actual notification value are retrieved with the fast call
+``OPTEE_SMC_GET_ASYNC_NOTIF_VALUE``. Note that one interrupt can represent
+multiple notifications.
+
+One notification value ``OPTEE_SMC_ASYNC_NOTIF_VALUE_DO_BOTTOM_HALF`` has a
+special meaning. When this value is received it means that normal world is
+supposed to make a yielding call ``OPTEE_MSG_CMD_DO_BOTTOM_HALF``. This
+call is done from the thread assisting the interrupt handler. This is a
+building block for OP-TEE OS in secure world to implement the top half and
+bottom half style of device drivers.
+
 AMD-TEE driver
 ==============