Some remarks below that I noticed after sending this. On Mon Mar 4, 2024 at 11:27 PM EET, Jarkko Sakkinen wrote: > Based recent discussions on LKML, provide preliminary bits of tpm_tis_core s/Based/ Based on/ > 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 s/to/into/ > +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 s/a kernel/kernel/ s/a commands/commands/ > +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. s/it sets/kernel relinquishes reservation by setting/ > + > +Pending localities are served in order by the chip descending orderm and > +one at a time: "Pending localities are served in descending order 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. s/on purpose/on the purpose/ BR, Jarkko
