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add boot origin description in BOOT0 header

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Signed-off-by: Michel-FK <michel.stempin@funkey-project.com>
This commit is contained in:
Michel-FK 2021-02-19 22:30:34 +01:00
parent 20c14a519d
commit 75df708565
1 changed files with 13 additions and 7 deletions
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20
docs/developer_guide/software_reference/boot_process/boot_rom.md
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@ -368,6 +368,11 @@ partitioning scheme:
On the **FunKey S**, the 8KB offset is used for the SPL, detailed in On the **FunKey S**, the 8KB offset is used for the SPL, detailed in
the next section. the next section.
The SD Card interface used (0 or 2) is stored into the BOOT0 header in
the byte at offset 40, and bit 5 in this byte is set to `1` when the
BOOT0 header is loaded from offset 128 KB, and to `0` when booted from
offset 8KB by this [code][45].
## FEL ## FEL
The FEL is a low-level subroutine also contained in the BootROM on The FEL is a low-level subroutine also contained in the BootROM on
@ -375,19 +380,19 @@ Allwinner devices. It is used for initial programming and recovery of
devices using USB. devices using USB.
The FEL is actually implementing a tiny USB stack for a [proprietary The FEL is actually implementing a tiny USB stack for a [proprietary
USB protocol][45] different from the standard DFU (Device Firmware USB protocol][46] different from the standard DFU (Device Firmware
Update) protocol used by many other devices. Update) protocol used by many other devices.
Using some specific tools on the host computer, it is possible to read Using some specific tools on the host computer, it is possible to read
or write data to/from the device over USB and execute code on it, or write data to/from the device over USB and execute code on it,
providing a way to boot the system over USB. providing a way to boot the system over USB.
These "sunxi-tools" are described [here][46] and [here][47]. These "sunxi-tools" are described [here][47] and [here][48].
!!! warning !!! warning
For the V3s, it is mandatory to build the version from the For the V3s, it is mandatory to build the version from the
[repository][48], as the versions packaged in the different [repository][49], as the versions packaged in the different
operating systems are too old and do not take into account the V3s operating systems are too old and do not take into account the V3s
chip. chip.
@ -443,7 +448,8 @@ includes/glossary.md
[42]: https://github.com/FunKey-Project/Allwinner-V3s-BROM/blob/main/brom.s#L7267-L7268 [42]: https://github.com/FunKey-Project/Allwinner-V3s-BROM/blob/main/brom.s#L7267-L7268
[43]: https://github.com/FunKey-Project/Allwinner-V3s-BROM/blob/main/brom.s#L3792-L3799 [43]: https://github.com/FunKey-Project/Allwinner-V3s-BROM/blob/main/brom.s#L3792-L3799
[44]: https://github.com/FunKey-Project/Allwinner-V3s-BROM/blob/main/brom.s#L3801-L3807 [44]: https://github.com/FunKey-Project/Allwinner-V3s-BROM/blob/main/brom.s#L3801-L3807
[45]: https://linux-sunxi.org/FEL/Protocol [45]: https://github.com/FunKey-Project/Allwinner-V3s-BROM/blob/main/brom.s#L3740-L3756
[46]: https://linux-sunxi.org/FEL/USBBoot [46]: https://linux-sunxi.org/FEL/Protocol
[47]: https://linux-sunxi.org/Sunxi-tools [47]: https://linux-sunxi.org/FEL/USBBoot
[48]: https://github.com/linux-sunxi/sunxi-tools [48]: https://linux-sunxi.org/Sunxi-tools
[49]: https://github.com/linux-sunxi/sunxi-tools