Documentation: Add FIT

Describe the Firmware Interface Table and reference useful documentation.

Change-Id: I00abc1fd13be7b48d56ba8cb65d2542ed07f9017
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32325
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

4 files changed, 193 insertions, 0 deletions

diff --git a/Documentation/soc/intel/fit.dia b/Documentation/soc/intel/fit.dia
new file mode 100644
index 0000000000..7e07978f71
--- /dev/null
+++ b/Documentation/soc/intel/fit.dia
diff --git a/Documentation/soc/intel/fit.md b/Documentation/soc/intel/fit.md
new file mode 100644
index 0000000000..8b638f0433
--- /dev/null
+++ b/Documentation/soc/intel/fit.md
@@ -0,0 +1,60 @@
+# Intel Firmware Interface Table
+
+The FIT allows to run code before the actual IA32 reset vector is executed
+by the CPU. The FIT resides in the BIOS region (usually near the reset vector)
+and is pointed to by the FIT pointer residing at `0xFFFFFFC0`.
+
+## Table layout
+The table consists of blocks each 16 bytes in size.
+The first is called *FIT header* the other are called *FIT entry*.
+
+![FIT in x86 memory map][fit]
+
+[fit]: fit.svg
+
+## Fit types
+
+Each entry has a *type* that give the other bits in the entry a different
+meaning. The following types are known:
+
+```eval_rst
++-----------+------------------------------------------------------------------+
+| no.       | Description                                                      |
++===========+==================================================================+
+|       0x0 | HEADER.                                                          |
++-----------+------------------------------------------------------------------+
+|       0x1 | MICROCODE.                                                       |
++-----------+------------------------------------------------------------------+
+|       0x2 | STARTUP_ACM.                                                     |
++-----------+------------------------------------------------------------------+
+|       0x7 | BIOS_STARTUP_MODULE.                                             |
++-----------+------------------------------------------------------------------+
+|       0x8 | TPM_POLICY.                                                      |
++-----------+------------------------------------------------------------------+
+|       0x9 | BIOS_POLICY.                                                     |
++-----------+------------------------------------------------------------------+
+|       0xa | TXT_POLICY.                                                      |
++-----------+------------------------------------------------------------------+
+|       0xb | KEY_MANIFEST.                                                    |
++-----------+------------------------------------------------------------------+
+|       0xc | BOOT_POLICY_MANIFEST.                                            |
++-----------+------------------------------------------------------------------+
+|      0x10 | CSE_SECURE_BOOT.                                                 |
++-----------+------------------------------------------------------------------+
+|      0x2d | TXTSX_POLICY.                                                    |
++-----------+------------------------------------------------------------------+
+|      0x2f | JMP_DEBUG_POLICY.                                                |
++-----------+------------------------------------------------------------------+
+|      0x7f | SKIP.                                                            |
++-----------+------------------------------------------------------------------+
+```
+
+## Usage in coreboot
+
+The most common usage of FIT is to use *Type1* to update microcode before
+execution of the IA32 reset vector happens.
+
+## References
+
+* [Intel TXT LAB handout](https://downloadmirror.intel.com/18931/eng/Intel%20TXT%20LAB%20Handout.pdf)
+* [FIT bios specification](https://www.intel.com/content/dam/www/public/us/en/documents/guides/fit-bios-specification.pdf)
diff --git a/Documentation/soc/intel/fit.svg b/Documentation/soc/intel/fit.svg
new file mode 100644
index 0000000000..eb6c696bb7
--- /dev/null
+++ b/Documentation/soc/intel/fit.svg
@@ -0,0 +1,132 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/PR-SVG-20010719/DTD/svg10.dtd">
+<svg width="15cm" height="11cm" viewBox="520 311 299 204" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+  <g>
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+    <rect style="fill: none; fill-opacity:0; stroke-width: 2; stroke: #ffffff" x="521.518" y="312.25" width="296.25" height="201.75"/>
+  </g>
+  <g>
+    <rect style="fill: #ffffff" x="689.333" y="321.667" width="72.375" height="173.833"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 2; stroke: #000000" x="689.333" y="321.667" width="72.375" height="173.833"/>
+    <text font-size="12.7998" style="fill: #000000;text-anchor:middle;font-family:sans-serif;font-style:normal;font-weight:normal" x="725.521" y="412.483">
+      <tspan x="725.521" y="412.483"></tspan>
+    </text>
+  </g>
+  <path style="fill: none; fill-opacity:0; stroke-width: 2; stroke: #000000" d="M 603.917 320.833 C 593.071,320.833 601.631,407 590.785,407"/>
+  <path style="fill: none; fill-opacity:0; stroke-width: 2; stroke: #000000" d="M 601.667 493.833 C 590.821,493.833 600.131,407.75 589.285,407.75"/>
+  <text font-size="12.7998" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="520.833" y="412">
+    <tspan x="520.833" y="412">bootblock</tspan>
+  </text>
+  <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke-dasharray: 4; stroke: #000000" x1="686.167" y1="352" x2="781.167" y2="352"/>
+  <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke-dasharray: 4; stroke: #000000" x1="685.8" y1="334.433" x2="780.8" y2="334.433"/>
+  <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke-dasharray: 4; stroke: #000000" x1="682.8" y1="410.933" x2="777.8" y2="410.933"/>
+  <g>
+    <path style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #0000ff" d="M 652.833,345.667 A 30.938,30.938 0 0 0 647.806,407.306"/>
+    <polygon style="fill: #0000ff" points="650.775,407.521 646.813,409.595 647.775,407.577 646.738,405.596 "/>
+    <polygon style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #0000ff" points="650.775,407.521 646.813,409.595 647.775,407.577 646.738,405.596 "/>
+  </g>
+  <g>
+    <rect style="fill: #ffffff" x="694.75" y="367" width="60.2083" height="10.5"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #0000ff" x="694.75" y="367" width="60.2083" height="10.5"/>
+  </g>
+  <text font-size="5.64436" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="653" y="323.333">
+    <tspan x="653" y="323.333">4 GiB </tspan>
+  </text>
+  <text font-size="5.64436" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="651.967" y="336.017">
+    <tspan x="651.967" y="336.017">4 GiB - 10h </tspan>
+  </text>
+  <text font-size="5.64436" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="653.633" y="410.183">
+    <tspan x="653.633" y="410.183">4 GiB - x </tspan>
+  </text>
+  <text font-size="5.64436" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="650.967" y="353.183">
+    <tspan x="650.967" y="353.183">4 GiB - 40 h </tspan>
+  </text>
+  <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #0000ff" x1="652.458" y1="346" x2="685" y2="345.833"/>
+  <text font-size="7.90222" style="fill: #0000ff;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="707.958" y="348.25">
+    <tspan x="707.958" y="348.25">FIT Ptr</tspan>
+  </text>
+  <text font-size="7.90222" style="fill: #ff0000;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="692.933" y="330.55">
+    <tspan x="692.933" y="330.55">IA32 reset vec</tspan>
+  </text>
+  <g>
+    <rect style="fill: #ffffff" x="693.183" y="449.25" width="60.2083" height="41.5333"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #ff0000" x="693.183" y="449.25" width="60.2083" height="41.5333"/>
+  </g>
+  <g>
+    <path style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #ff0000" d="M 655.208,326.75 A 61.4124,61.4124 0 0 0 645.824,444.152"/>
+    <polygon style="fill: #ff0000" points="648.64,445.169 644.228,445.895 645.775,444.281 645.412,442.075 "/>
+    <polygon style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #ff0000" points="648.64,445.169 644.228,445.895 645.775,444.281 645.412,442.075 "/>
+  </g>
+  <text font-size="5.64436" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="653.683" y="449.95">
+    <tspan x="653.683" y="449.95">4 GiB - z </tspan>
+  </text>
+  <g>
+    <rect style="fill: #ffffff" x="693.683" y="432" width="60.2083" height="12"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #ff0000" x="693.683" y="432" width="60.2083" height="12"/>
+  </g>
+  <g>
+    <rect style="fill: #ffffff" x="693.933" y="416.2" width="60.2083" height="12"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #00ff00" x="693.933" y="416.2" width="60.2083" height="12"/>
+  </g>
+  <text font-size="5.64436" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="653.183" y="432.2">
+    <tspan x="653.183" y="432.2">4 GiB - y </tspan>
+  </text>
+  <text font-size="6.77333" style="fill: #ff0000;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="717.208" y="440">
+    <tspan x="717.208" y="440">ACM</tspan>
+  </text>
+  <text font-size="6.77333" style="fill: #ff0000;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="706.433" y="467">
+    <tspan x="706.433" y="467">BOOTBLOCK</tspan>
+    <tspan x="706.433" y="475.467">CODE</tspan>
+  </text>
+  <text font-size="6.77333" style="fill: #00ff00;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="714.183" y="424.25">
+    <tspan x="714.183" y="424.25">uCode</tspan>
+  </text>
+  <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #ff0000" x1="655.186" y1="327.119" x2="687.728" y2="326.953"/>
+  <g>
+    <rect style="fill: #ffffff" x="694.683" y="377.45" width="60.2083" height="10.5"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #0000ff" x="694.683" y="377.45" width="60.2083" height="10.5"/>
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+    <rect style="fill: #ffffff" x="694.75" y="387.95" width="60.2083" height="10.5"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #0000ff" x="694.75" y="387.95" width="60.2083" height="10.5"/>
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+  <g>
+    <rect style="fill: #ffffff" x="694.683" y="398.4" width="60.2083" height="10.5"/>
+    <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #0000ff" x="694.683" y="398.4" width="60.2083" height="10.5"/>
+  </g>
+  <text font-size="5.64444" style="fill: #0000ff;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="706.433" y="406.25">
+    <tspan x="706.433" y="406.25">FIT header</tspan>
+  </text>
+  <text font-size="5.64444" style="fill: #0000ff;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="703.933" y="394.95">
+    <tspan x="703.933" y="394.95">Type1 entry</tspan>
+  </text>
+  <text font-size="5.64444" style="fill: #0000ff;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="703.933" y="384.7">
+    <tspan x="703.933" y="384.7">Type2 entry</tspan>
+  </text>
+  <text font-size="5.64444" style="fill: #0000ff;text-anchor:start;font-family:monospace;font-style:normal;font-weight:normal" x="703.683" y="373.95">
+    <tspan x="703.683" y="373.95">Type7 entry</tspan>
+  </text>
+  <g>
+    <path style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #90c9ff" d="M 769.4,417.215 A 13.2412,13.2412 0 0 0 763.208,391.5"/>
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+  <g>
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diff --git a/Documentation/soc/intel/index.md b/Documentation/soc/intel/index.md
index 4f6b4f21b6..86f4de7155 100644
--- a/Documentation/soc/intel/index.md
+++ b/Documentation/soc/intel/index.md
@@ -8,3 +8,4 @@ This section contains documentation about coreboot on specific Intel SOCs.
 - [FSP](fsp/index.md)
 - [Ice Lake/9th Gen Core-i series](icelake/index.md)
 - [MP Initialization](mp_init/mp_init.md)
+- [Firmware Interface Table](fit.md)