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feat(U-Boot): Add User Guide on Key Writer Lite
Add a user guide that introduces and gives an example flow of key writer lite from u-boot. Signed-off-by: Harsha Vardhan V M <[email protected]>
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‎configs/AM62LX/AM62LX_linux_toc.txt

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@@ -31,6 +31,7 @@ linux/Foundational_Components/U-Boot/UG-Memory-K3
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linux/Foundational_Components/U-Boot/UG-SPI
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linux/Foundational_Components/U-Boot/UG-QSPI
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linux/Foundational_Components/U-Boot/UG-UART
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linux/Foundational_Components/U-Boot/UG-Key-Writer-Lite
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linux/Foundational_Components/U-Boot/Applications
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linux/Foundational_Components/U-Boot/Apps-SPL-Debug-OpenOCD

‎source/images/Uboot_fuse_writebuff_OTP_structure.png

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‎source/linux/Foundational_Components/U-Boot/UG-General-Info.rst

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│ ROM Data │ │ PSRAM (64k)
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│ │ │
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└────────────────────┘ 0x707F_0000 ┴
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.. ifconfig:: CONFIG_part_variant in ('AM62LX')
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OTP Key Writer Lite
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^^^^^^^^^^^^^^^^^^^
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The OTP (One Time Programmable) key writer lite guide to populate customer
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keys in eFuses of the SoC can be found :ref:`here <key-writer-lite-label>`.

‎source/linux/Foundational_Components/U-Boot/UG-Key-Writer-Lite.rst

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.. _key-writer-lite-label:
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Key Writer Lite
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---------------
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This OTP (One Time Programmable) key writer lite guide describes
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the procedure to be followed to populate customer keys in eFuses
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of the SoC. Once the SoC eFuses are programmed using keywriter lite,
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there is no going back. This action of burning the OTP fields is
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irreversible.
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**High Security (HS) Device Sub-types**
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*HS-FS (High Security - Field Securable)*:
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Device type before customer keys are programmed (the state in which
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the device leaves TI factory). In this state, device protects the
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ROM code, TI keys and certain security peripherals. HS-FS devices do
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not enforce secure boot process.
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*HS-SE Lite (High Security - Security Enforced Lite)*:
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Device type after only the customer public key hashes are programmed.
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HS-SE Lite devices enforce secure boot (without encryption).
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**HS-FS to HS-SE Lite Conversion**
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In order to convert a HS-FS device to HS-SE Lite device, one has to
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program the customer root key (optionally backup key) on the target
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device, using OTP Keywriter Lite.
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Customer key information is put in a structured format to create a
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binary blob (Uboot key writer lite structure).
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**Uboot Key Writer Lite Structure**
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.. code-block:: text
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struct fuse_otp_header {
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uint32_t version_info;
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uint32_t fuse_mode;
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} __attribute__((packed));
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struct fuse_otp {
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struct fuse_otp_header fuse_otp_hdr;
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struct fuse_otp_blob fuse_otp_blb;
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} __attribute__((packed));
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* version_info : Customer can use this field to denote the version of uboot fuse programming.
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* fuse_mode : Fuse mode with value 0x00009045.
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The overall fuse_otp structure is shown below:
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.. Image:: /images/Uboot_fuse_writebuff_OTP_structure.png
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For information on the fuse_otp_blob structure,
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visit `keywriter_lite_cert_gen_procedure`_.
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.. _keywriter_lite_cert_gen_procedure: https://software-dl.ti.com/tisci/esd/latest/6_topic_user_guides/key_writer_lite.html
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**Generate the Binary Blob**
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Generate the binary blob based out of Uboot Key Writer Lite
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structure by populating the structure and extracting the
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.data section to a bin file and copy it to SD card.
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**Typical Key Writer Lite Flow**
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A typical flow to do OTP key writer lite is as follows:
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#. Addr 0x82000000 is the dedicated address to store the generated
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key writer lite binary blob. Clear out 1Kb of memory starting
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from 0x82000000:
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.. code-block:: text
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u-boot=> mw 0x82000000 0 0x400
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#. The binary blob copied to SD card can be loaded into memory using
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commands like:
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.. code-block:: text
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u-boot=> fatload mmc 1:1 0x82000000 key_writer_lite_blob.bin
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#. If the cache has to be flushed, then enable the config
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CONFIG_CMD_CACHE=y in <path-to-tisdk>/board-support/<ti-u-boot-source-code>/configs/<device_defconfig>
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and re-build uboot.
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.. code-block:: text
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u-boot=> dcache flush
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u-boot=> md 0x82000000
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#. Efuse modification requires a voltage to be applied on a specific pin (Vpp) during the programming.
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To program the efuses, the Vpp pin on the System-on-Chip (SoC) must be powered at 1.8V. It is the
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responsibility of the SoC user to design a suitable circuit that enables the Vpp pin to be powered.
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Texas Instruments (TI) EVMs feature an I2C-based IO expander, which has one of its IO pins
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connected to the SoC's Vpp pin. The software required to control the power to the Vpp pin depends
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on the specific circuit implementation.
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In the case of TI AM62L PROC181E1 EVMs, an I2C driver is necessary to send command packets to the IO expander,
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which then toggles the IO pin connected to the Vpp pin, thereby controlling the power supply to the pin.
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On TI EVM, Vpp pin can be turned on using the below commands:
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.. code-block:: text
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u-boot=> i2c dev 2
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u-boot=> i2c probe 22
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.. rubric:: To turn off Vpp:
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.. code-block:: text
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u-boot=> i2c mw 0x22 0x04 0x00
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.. rubric:: To configure Vpp (port 04) as output:
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.. code-block:: text
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u-boot=> i2c mw 0x22 0xC 0xEF
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.. rubric:: To turn on Vpp:
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.. code-block:: text
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u-boot=> i2c mw 0x22 0x04 0x10
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#. Call fuse writebuff sub-system command with the address 0x82000000:
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.. code-block:: text
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u-boot=> fuse writebuff -y 0x82000000
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#. Turn off Vpp after programming is successful:
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.. code-block:: text
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u-boot=> i2c mw 0x22 0x04 0x00
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Changes made to efuses, by programming them, take effect (like become
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visible in Memory-Mapped Registers (MMRs), device type change etc.)
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after a complete System-on-Chip (SoC) power cycle.

‎source/linux/Foundational_Components/U-Boot/Users-Guide.rst

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UG-AVS
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UG-Thermal
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UG-Splash-Screen
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UG-Key-Writer-Lite

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