Add documentation for the Qualcomm TEE driver.
Acked-by: Sumit Garg sumit.garg@oss.qualcomm.com Signed-off-by: Amirreza Zarrabi amirreza.zarrabi@oss.qualcomm.com --- Documentation/tee/index.rst | 1 + Documentation/tee/qtee.rst | 96 +++++++++++++++++++++++++++++++++++++++++++++ MAINTAINERS | 1 + 3 files changed, 98 insertions(+)
diff --git a/Documentation/tee/index.rst b/Documentation/tee/index.rst index 4be6e69d7837..62afb7ee9b52 100644 --- a/Documentation/tee/index.rst +++ b/Documentation/tee/index.rst @@ -11,6 +11,7 @@ TEE Subsystem op-tee amd-tee ts-tee + qtee
.. only:: subproject and html
diff --git a/Documentation/tee/qtee.rst b/Documentation/tee/qtee.rst new file mode 100644 index 000000000000..2fa2c1bf6384 --- /dev/null +++ b/Documentation/tee/qtee.rst @@ -0,0 +1,96 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================================= +QTEE (Qualcomm Trusted Execution Environment) +============================================= + +The QTEE driver handles communication with Qualcomm TEE [1]. + +The lowest level of communication with QTEE builds on the ARM SMC Calling +Convention (SMCCC) [2], which is the foundation for QTEE's Secure Channel +Manager (SCM) [3] used internally by the driver. + +In a QTEE-based system, services are represented as objects with a series of +operations that can be called to produce results, including other objects. + +When an object is hosted within QTEE, executing its operations is referred +to as "direct invocation". QTEE can also invoke objects hosted in the non-secure +world using a method known as "callback request". + +The SCM provides two functions to support direct invocation and callback requests: + +- QCOM_SCM_SMCINVOKE_INVOKE: Used for direct invocation. It can return either + a result or initiate a callback request. +- QCOM_SCM_SMCINVOKE_CB_RSP: Used to submit a response to a callback request + triggered by a previous direct invocation. + +The QTEE Transport Message [4] is stacked on top of the SCM driver functions. + +A message consists of two buffers shared with QTEE: inbound and outbound +buffers. The inbound buffer is used for direct invocation, and the outbound +buffer is used to make callback requests. This picture shows the contents of +a QTEE transport message:: + + +---------------------+ + | v + +-----------------+-------+-------+------+--------------------------+ + | qcomtee_msg_ |object | buffer | | + | object_invoke | id | offset, size | | (inbound buffer) + +-----------------+-------+--------------+--------------------------+ + <---- header -----><---- arguments ------><- in/out buffer payload -> + + +-----------+ + | v + +-----------------+-------+-------+------+----------------------+ + | qcomtee_msg_ |object | buffer | | + | callback | id | offset, size | | (outbound buffer) + +-----------------+-------+--------------+----------------------+ + +Each buffer is started with a header and array of arguments. + +QTEE Transport Message supports four types of arguments: + +- Input Object (IO) is an object parameter to the current invocation + or callback request. +- Output Object (OO) is an object parameter from the current invocation + or callback request. +- Input Buffer (IB) is (offset, size) pair to the inbound or outbound region + to store parameter to the current invocation or callback request. +- Output Buffer (OB) is (offset, size) pair to the inbound or outbound region + to store parameter from the current invocation or callback request. + +Picture of the relationship between the different components in the QTEE +architecture:: + + User space Kernel Secure world + ~~~~~~~~~~ ~~~~~~ ~~~~~~~~~~~~ + +--------+ +----------+ +--------------+ + | Client | |callback | | Trusted | + +--------+ |server | | Application | + /\ +----------+ +--------------+ + || +----------+ /\ /\ + || |callback | || || + || |server | || / + || +----------+ || +--------------+ + || /\ || | TEE Internal | + || || || | API | + / / / +--------+--------+ +--------------+ + +---------------------+ | TEE | QTEE | | QTEE | + | libqcomtee [5] | | subsys | driver | | Trusted OS | + +-------+-------------+--+----+-------+----+-------------+--------------+ + | Generic TEE API | | QTEE MSG | + | IOCTL (TEE_IOC_*) | | SMCCC (QCOM_SCM_SMCINVOKE_*) | + +-----------------------------+ +---------------------------------+ + +References +========== + +[1] https://docs.qualcomm.com/bundle/publicresource/topics/80-70015-11/qualcomm-... + +[2] http://infocenter.arm.com/help/topic/com.arm.doc.den0028a/index.html + +[3] drivers/firmware/qcom/qcom_scm.c + +[4] drivers/tee/qcomtee/qcomtee_msg.h + +[5] https://github.com/quic/quic-teec diff --git a/MAINTAINERS b/MAINTAINERS index bde449308736..589f8ea62bcf 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -20860,6 +20860,7 @@ QUALCOMM TEE (QCOMTEE) DRIVER M: Amirreza Zarrabi amirreza.zarrabi@oss.qualcomm.com L: linux-arm-msm@vger.kernel.org S: Maintained +F: Documentation/tee/qtee.rst F: drivers/tee/qcomtee/
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