| Message ID | 20240321164314.14732-1-jarkko@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] Documentation: tpm_tis | expand |
On Thu Mar 21, 2024 at 6:43 PM EET, Jarkko Sakkinen wrote: > 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. $ pdftotext PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p05p_r14_pub.pdf $ grep -ci 'FIFO interface' PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p05p_r14_pub.txt 55 $ grep -ci 'TIS interface' PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p05p_r14_pub.txt 2 55 > 2 so that pretty much nails this terminology. BR, Jarkko
On Thu Mar 21, 2024 at 6:54 PM EET, Jarkko Sakkinen wrote: > On Thu Mar 21, 2024 at 6:43 PM EET, Jarkko Sakkinen wrote: > > 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. > > $ pdftotext PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p05p_r14_pub.pdf > $ grep -ci 'FIFO interface' PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p05p_r14_pub.txt > 55 > > $ grep -ci 'TIS interface' PC-Client-Specific-Platform-TPM-Profile-for-TPM-2p0-v1p05p_r14_pub.txt > 2 > > 55 > 2 so that pretty much nails this terminology. To add, this documentation *clears* the confusion in "FIFO vs TIS" by documenting where TIS comes from (i.e. from the original TPM Interface Spefication). If you read the current standards you bump quite often (55 times in the current spec) to FIFO interface, so it is good to clarify their relation in the kernel documentation. BR, Jarkko
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..078b75666086 --- /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" comes from the TPM Interface +Specification, which is the hardware interface specification for TPM 1.x chips. + +Communication is based on a 20 KiB buffer shared by the TPM chip through a +hardware bus or memory map, depending on the physical wiring. The buffer is +further split into five equal-size 4 KiB buffers, which provide equivalent +sets of registers for communication between the CPU and TPM. These +communication endpoints are called localities in the TCG terminology. + +When the kernel wants to send commands to the TPM chip, it first reserves +locality 0 by setting the requestUse bit in the TPM_ACCESS register. The bit is +cleared by the chip when the access is granted. Once it completes its +communication, the kernel writes the TPM_ACCESS.activeLocality bit. This +informs the chip that the locality has been relinquished. + +Pending localities are served in order by the chip in descending order, one at +a time: + +- Locality 0 has the lowest priority. +- Locality 5 has the highest priority. + +Further information on the purpose and meaning of the localities can be found +in section 3.2 of the TCG PC Client Platform TPM Profile Specification.