linux-kernel - Re: [PATCH v6 1/6] docs: staging/tee.rst: add a section on OP-TEE notifications

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Message-ID: <CAFA6WYPLCLmYhSa_-vJPvhy9fFpdD3u39YZenYgij4fSM-+JCw@mail.gmail.com>
Date:   Wed, 13 Oct 2021 12:32:01 +0530
From:   Sumit Garg <sumit.garg@...aro.org>
To:     Jens Wiklander <jens.wiklander@...aro.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        OP-TEE TrustedFirmware <op-tee@...ts.trustedfirmware.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Jerome Forissier <jerome@...issier.org>,
        Etienne Carriere <etienne.carriere@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Ard Biesheuvel <ardb@...nel.org>, Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH v6 1/6] docs: staging/tee.rst: add a section on OP-TEE notifications

On Wed, 6 Oct 2021 at 12:45, Jens Wiklander <jens.wiklander@...aro.org> wrote:
>
> Adds a section on notifications used by OP-TEE, synchronous and
> asynchronous.
>
> Acked-by: Marc Zyngier <maz@...nel.org>
> Signed-off-by: Jens Wiklander <jens.wiklander@...aro.org>
> ---
>  Documentation/staging/tee.rst | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>

Reviewed-by: Sumit Garg <sumit.garg@...aro.org>

-Sumit

> 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
>  ==============
>
> --
> 2.31.1
>