security/tpm/tpm_ffa_crb.rst

1 .. SPDX-License-Identifier: GPL-2.0
4 TPM CRB over FF-A Driver
13 - hardware registers in a discrete TPM chip
15 - in memory for a TPM running in isolated environment where shared memory
18 The Firmware Framework for Arm A-profile (FF-A) [2]_ is a specification
21 - Compartmentalize firmware into software partitions that run in the Arm
24 - Provide a standard interface for software components in the Non-secure
27 A TPM can be implemented as an FF-A secure service.  This could be a firmware
28 TPM or could potentially be a TPM service that acts as a proxy to a discrete
29 TPM chip. An FF-A based TPM abstracts hardware details (e.g. bus controller
31 by an OS.  The TCG-defined CRB interface is used by clients to interact
32 with the TPM service.
34 The Arm TPM Service Command Response Buffer Interface Over FF-A [3]_
35 specification defines FF-A messages that can be used by a client to signal
38 How the Linux CRB driver interacts with FF-A is summarized below:
40 - The tpm_crb_ffa driver registers with the FF-A subsystem in the kernel
41   with an architected TPM service UUID defined in the CRB over FF-A spec.
43 - If a TPM service is discovered by FF-A, the probe() function in the
46 - The probing and initialization of the Linux CRB driver is triggered
49   method for Arm FF-A was defined in TCG ACPI v1.4 [4]_.
51 - When the CRB driver performs its normal functions such as signaling 'start'
53   in the tpm_crb_ffa driver which handles the FF-A messaging to the TPM.
59    https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
60 .. [2] **Arm Firmware Framework for Arm A-profile (FF-A)**
61    https://developer.arm.com/documentation/den0077/latest/
62 .. [3] **Arm TPM Service Command Response Buffer Interface Over FF-A**
63    https://developer.arm.com/documentation/den0138/latest/
65    https://trustedcomputinggroup.org/resource/tcg-acpi-specification/