On Tue Mar 5, 2024 at 12:53 AM EET, Randy Dunlap wrote: > > > On 3/4/24 13:27, 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. > > > > 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/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. > > Is that activeLocality ? Yes. > > > + > > +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. > > priority. > > > + > > +Further information on purpose and meaning of the localities can be found > > +from section 3.2 of TCG PC Client Platform TPM Profile Specification. Thanks for the remarks. Too many typos but at least I think the story is is understandable and describes pretty well key elements of tpm_tis_core. BR, Jarkko
