Based recent discussions on LKML, provide preliminary bits of tpm_tis_core dependent drivers. Includes only bare essentials but can be extended later on case by case. This way some people may even want to read it later on. Cc: Jonathan Corbet <corbet@xxxxxxx> CC: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx> Cc: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxx> Cc: Peter Huewe <peterhuewe@xxxxxx> Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> Cc: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx> Cc: keyrings@xxxxxxxxxxxxxxx Cc: linux-doc@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-integrity@xxxxxxxxxxxxxxx Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> --- Documentation/security/tpm/index.rst | 1 + Documentation/security/tpm/tpm_tis.rst | 30 ++++++++++++++++++++++++++ 2 files changed, 31 insertions(+) create mode 100644 Documentation/security/tpm/tpm_tis.rst diff --git a/Documentation/security/tpm/index.rst b/Documentation/security/tpm/index.rst index fc40e9f23c85..f27a17f60a96 100644 --- a/Documentation/security/tpm/index.rst +++ b/Documentation/security/tpm/index.rst @@ -5,6 +5,7 @@ Trusted Platform Module documentation .. toctree:: tpm_event_log + tpm_tis tpm_vtpm_proxy xen-tpmfront tpm_ftpm_tee diff --git a/Documentation/security/tpm/tpm_tis.rst b/Documentation/security/tpm/tpm_tis.rst new file mode 100644 index 000000000000..3cec0216a169 --- /dev/null +++ b/Documentation/security/tpm/tpm_tis.rst @@ -0,0 +1,30 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================= +TPM FIFO interface Driver +========================= + +FIFO (First-In-First-Out) is the name of the hardware interface used by the +`tpm_tis_core` dependent drivers. The prefix "tis" is named after TPM +Interface Specification, which is the hardware interface specification for +TPM 1.x chips. + +Communication is based on a 5 KiB buffer shared by the TPM chip through a +hardware bus or memory map. The buffer is further split to five equal size +buffers, which provide equivalent sets of registers for communication +between CPU and TPM. The communication end points are called *localities* +in the TCG terminology. + +When a kernel wants to send a commands to the TPM chip, it first reserves +locality 0 by setting `requestUse` bit in `TPM_ACCESS` register. The bit is +cleared by the chip when the access is granted. Once completed its +communication, it sets `activeLocity` bit in the same register. + +Pending localities are served in order by the chip descending orderm and +one at a time: + +- Locality 0 has the lowest priority. +- Locality 5 has the highest priotiy. + +Further information on purpose and meaning of the localities can be found +from section 3.2 of TCG PC Client Platform TPM Profile Specification. -- 2.40.1