docs/fingerprint: Add factory quick guide

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BRANCH=none
TEST=View Markdown in gitiles

Change-Id: I0cba21879388ac228d306f54011e020130b0a233
Signed-off-by: Philip Chen <philipchen@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2116494
Reviewed-by: Tom Hughes <tomhughes@chromium.org>
Commit-Queue: Tom Hughes <tomhughes@chromium.org>
Tested-by: Tom Hughes <tomhughes@chromium.org>

1 files changed, 97 insertions, 0 deletions

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+# Chrome OS Fingerprint Sensor: Quick Factory Guide
+
+The goal of this document is to outline how ODM partners can make use of the
+existing Chrome OS factory scripts to meet Chrome OS FPS factory requirements.
+
+[TOC]
+
+## Factory Requirements
+
+### Flash firmware for fingerprint sensor microcontroller (FPMCU)
+
+FPMCU firmware must be flashed before fingerprint functional test is run. ODM
+partners may work with the module house to preflash FPMCU firmware before
+factory SMT. However, this way ODM partners have to coordinate with the module
+house to make sure the preflash FPMCU firmware blob is extracted from the FSI
+release image (from /opt/google/biod/fw/). If the FPMCU firmware doesn’t match
+the FPMCU firmware blob checked into the release image, the end users will see
+the ‘critical update’ screen in their out-of-box experience, because
+bio\_fw\_updater tries to update FPMCU firmware at boot time. This is a bad user
+experience we want to avoid. Most importantly, in PVT/MP build, only the FPMCU
+firmware in the release image would be signed by MP key. So you **MUST** ensure
+FPMCU is flashed with the MP-signed firmware blob extracted from FSI, before
+shipping the devices.
+
+As opposed to pre-flashing FPMCU in the module house, ODM partners are
+encouraged to make use of
+[update\_fpmcu\_firmware.py](https://chromium.googlesource.com/chromiumos/platform/factory/+/e5e903d0a0d8327dd8b9e47d2c808fd845ed73a4/py/test/pytests/update_fpmcu_firmware.py)
+to update FPMCU firmware in the factory flow. This script can detect fingerprint
+MCU board name, find the right FPMCU firmware blob for the DUT from the release
+partition, and then flash FPMCU by flash\_fp\_mcu tool. Please note that this
+script may take more than 30 secs to complete, which is slow.
+
+Since bio\_fw\_update has been disabled in factory test image via
+[crrev/c/1913645](https://chromium-review.googlesource.com/c/chromiumos/platform2/+/1913645),
+in the factory flow, the FPMCU firmware should not be overwritten by
+boot-update-firmware service during reboot.
+
+### Run fingerprint sensor functional test
+
+Please add
+[fingerprint\_mcu.py](https://chromium.git.corp.google.com/chromiumos/platform/factory/+/a283609cd8446ba4a4b75c2e1d84c9ba24ea8422/py/test/pytests/fingerprint_mcu.py)
+to your device test list. A more detailed description about this test can be
+found
+[here](https://chromium.googlesource.com/chromiumos/platform/ec/+/refs/heads/master/docs/fingerprint/fingerprint-factory-requirements.md).
+
+### Initialize FPMCU entropy in factory finalization
+
+The support for FPMCU entropy initialization has been integrated into the
+factory finalization script. So FPMCU entropy should be automatically
+initialized in factory finalization, if a FPMCU is found on DUT. Note that FPMCU
+entropy initialization would fail if rollback\_block\_id is not equal to zero,
+which means the entropy has been initialized before. It is usually caused by
+biod trying to initialize FPMCU entropy and increment rollback\_block\_id at
+boot time. Since we have disabled biod and bio\_crypto\_init in factory test
+image via
+[crrev/c/1910290](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1910290),
+we expect rollback\_block\_id would stay zero during the factory flow, and FPMCU
+entropy initialization should succeed in factory finalization. So just run
+factory finalization as any other CrOS boards.
+
+### Enable FPMCU software write protection (SWWP) in factory finalization in PVT/MP
+
+The support for FPMCU SWWP has been integrated into factory finalization script.
+So FPMCU SWWP should be automatically enabled in factory finalization together
+with AP/EC SWWP when write\_protection arg is set to true and a FPMCU is found
+on DUT. Just run factory finalization as any other CrOS boards.
+
+### Reset entropy for factory re-finalization (in case of RMA or OQC)
+
+For the boards that have been finalized, FPMCU entropy has been initialized. So
+running re-finalization for those boards are expected to fail at FPMCU entropy
+initialization. Before running re-finalization for those boards, ODM partners
+have to remove hardware write protection (HWWP) and then run
+[update\_fpmcu\_firmware.py](https://chromium.googlesource.com/chromiumos/platform/factory/+/d399a0a1bdeb7249de2721b269e7365e4486e23c/py/test/pytests/update_fpmcu_firmware.py)
+to reset rollback\_block\_id and entropy. So the follow-up re-finalization
+(which re-initialize entropy) can succeed.
+
+## References
+
+*   CrOS fingerprint factory requirements:
+    [doc link](https://chromium.googlesource.com/chromiumos/platform/ec/+/refs/heads/master/docs/fingerprint/fingerprint-factory-requirements.md)
+*   The summary of CLs:
+    *   Add a factory script to update FPMCU firmware:
+        [crrev/c/1918679](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1918679),
+        [crrev/c/1913493](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1913493),
+        [crrev/c/1927149](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1927149),
+        [crrev/c/1984618](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1984618),
+        [crrev/c/2036574](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/2036574)
+    *   Disable FPS-related services that will interfere with the factory flow:
+        [crrev/c/1913645](https://chromium-review.googlesource.com/c/chromiumos/platform2/+/1913645),
+        [crrev/c/1910290](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1910290)
+    *   Support FPMCU in factory finalization:
+        [crrev/c/1868795](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1868795),
+        [crrev/c/1902267](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1902267),
+        [crrev/c/1900503](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1900503),
+        [crrev/c/1925927](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1925927),
+        [crrev/c/1948163](https://chromium-review.googlesource.com/c/chromiumos/platform/factory/+/1948163)