1 .. SPDX-License-Identifier: GPL-2.0
2
3 =========================
4 TPM FIFO interface driver
5 =========================
6
7 TCG PTP Specification defines two interface ty
8 based on sequenced read and write operations,
9 buffer containing the full command or response
10
11 FIFO (First-In-First-Out) interface is used by
12 drivers. Originally Linux had only a driver ca
13 memory mapped (aka MMIO) interface but it was
14 physical interfaces supported by the TCG stand
15
16 For historical reasons above the original MMIO
17 framework for FIFO drivers is named as tpm_tis
18 tpm_tis comes from the TPM Interface Specifica
19 interface specification for TPM 1.x chips.
20
21 Communication is based on a 20 KiB buffer shar
22 hardware bus or memory map, depending on the p
23 further split into five equal-size 4 KiB buffe
24 sets of registers for communication between th
25 communication endpoints are called localities
26
27 When the kernel wants to send commands to the
28 locality 0 by setting the requestUse bit in th
29 cleared by the chip when the access is granted
30 communication, the kernel writes the TPM_ACCES
31 informs the chip that the locality has been re
32
33 Pending localities are served in order by the
34 a time:
35
36 - Locality 0 has the lowest priority.
37 - Locality 5 has the highest priority.
38
39 Further information on the purpose and meaning
40 in section 3.2 of the TCG PC Client Platform T
41
42 References
43 ==========
44
45 TCG PC Client Platform TPM Profile (PTP) Speci
46 https://trustedcomputinggroup.org/resource/pc-
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