Hi, On 3/20/24 01:56, 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 > Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> Makes sense to me. Thanks. Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > --- > v2: > - Fixed errors reported by Randy: > https://lore.kernel.org/all/aed28265-d677-491a-a045-24b351854b24@xxxxxxxxxxxxx/ > - Improved the text a bit to have a better presentation. > --- > 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..b331813b3c45 > --- /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 5 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 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. -- #Randy
