[PATCH] Documentation: i.MX8M: add EVK barebox installation documentation

[Ulrich Ölmann]

Hi Ahmad,

just a small copied'n'pasted typo:

On Tue, Jan 03 2023 at 22:54 +0100, Ahmad Fatoum <a.fatoum at pengutronix.de> wrote:
> The barebox i.MX images have a preamble that pads the i.MX header to the
> offset expected by the BootROM. This allows writing barebox images
> directly to offset 0 on SD-Cards and eMMC user area. For some i.MX8M,
> these images can't be directly written to eMMC boot partitions and
> instead require special handling. Add a note about this to the
> documentation.
>
> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
> ---
>  Documentation/boards/imx/nxp-imx8mm-evk.rst | 18 ++++++++++++++++
>  Documentation/boards/imx/nxp-imx8mn-evk.rst | 24 +++++++++++++++++++++
>  Documentation/boards/imx/nxp-imx8mp-evk.rst | 24 +++++++++++++++++++++
>  3 files changed, 66 insertions(+)
>
> diff --git a/Documentation/boards/imx/nxp-imx8mm-evk.rst b/Documentation/boards/imx/nxp-imx8mm-evk.rst
> index c3cd35ae38a2..7ed7459c08a6 100644
> --- a/Documentation/boards/imx/nxp-imx8mm-evk.rst
> +++ b/Documentation/boards/imx/nxp-imx8mm-evk.rst
> @@ -69,3 +69,21 @@ board for serial download mode as printed on the PCB. You can start barebox with
>  the imx-usb-loader tool that comes with barebox like this:
>  
>  ./scripts/imx/imx-usb-loader images/barebox-nxp-imx8mm-evk.img
> +
> +Installing barebox
> +==================
> +
> +When the EVK is strapped to boot from eMMC, the i.MX8M bootrom will
> +consult the eMMC ext_csd register to determine whether to boot
> +from the active eMMC boot partition or from the user area.
> +
> +The same barebox image written to the start of the SD-Card can
> +be written to the start of the eMMC user area. Power-fail installation
> +to the eMMC boot partition requires special handling:
> +
> +  - The barebox image must be written to the inactive boot partition,
> +    then afterwards, the newly written boot partition is activated
> +    (This is controlled by the barebox ``mmcX.boot`` variable).
> +
> +The ``barebox_update`` command takes care of this and need just be
> +supplied a barebox image as argument.
> diff --git a/Documentation/boards/imx/nxp-imx8mn-evk.rst b/Documentation/boards/imx/nxp-imx8mn-evk.rst
> index b920e22d33e9..4c07b949dafb 100644
> --- a/Documentation/boards/imx/nxp-imx8mn-evk.rst
> +++ b/Documentation/boards/imx/nxp-imx8mn-evk.rst
> @@ -58,3 +58,27 @@ Build barebox
>  
>   make imx_v8_defconfig
>   make
> +
> +Installing barebox
> +==================
> +
> +When the EVK is strapped to boot from eMMC, the i.MX8M bootrom will
> +consult the eMMC ext_csd register to determine whether to boot
> +from the active eMMC boot partition or from the user area.
> +
> +The same barebox image written to the start of the SD-Card can
> +be written to the start of the eMMC user area. Power-fail installation
> +to the eMMC boot partition requires special handling:
> +
> +  - The barebox image must be written to the inactive boot partition,
> +    then afterwards, the newly written boot partition is activated
> +    (This is controlled by the barebox ``mmcX.boot`` variable).
> +
> +  - The barebox image includes a 32KiB preamble that allows the image
> +    to be directly writable to the start of the SD-Card or eMMC user area.
> +    Unlike older i.MX8M, the i.MX8MN BootROM expects the bootloader to not
> +    start as an offset when booting from eMMC boot partitions, thus the first

s/start as an offset/start at an offset/

> +    32KiB must be stripped.
> +
> +The ``barebox_update`` command takes care of this and need just be
> +supplied a barebox image as argument.
> diff --git a/Documentation/boards/imx/nxp-imx8mp-evk.rst b/Documentation/boards/imx/nxp-imx8mp-evk.rst
> index 1074992f2f88..60e9f9eaea5d 100644
> --- a/Documentation/boards/imx/nxp-imx8mp-evk.rst
> +++ b/Documentation/boards/imx/nxp-imx8mp-evk.rst
> @@ -66,3 +66,27 @@ Boot Configuration
>  The NXP i.MX8MP-EVK board has four switches responsible for configuring
>  bootsource/boot mode. The settings for the different boot sources are
>  printed on the board.
> +
> +Installing barebox
> +==================
> +
> +When the EVK is strapped to boot from eMMC, the i.MX8M bootrom will
> +consult the eMMC ext_csd register to determine whether to boot
> +from the active eMMC boot partition or from the user area.
> +
> +The same barebox image written to the start of the SD-Card can
> +be written to the start of the eMMC user area. Power-fail installation
> +to the eMMC boot partition requires special handling:
> +
> +  - The barebox image must be written to the inactive boot partition,
> +    then afterwards, the newly written boot partition is activated
> +    (This is controlled by the barebox ``mmcX.boot`` variable).
> +
> +  - The barebox image includes a 32KiB preamble that allows the image
> +    to be directly writable to the start of the SD-Card or eMMC user area.
> +    Unlike older i.MX8M, the i.MX8MP BootROM expects the bootloader to not
> +    start as an offset when booting from eMMC boot partitions, thus the first

s/start as an offset/start at an offset/

Best regards
Ulrich


> +    32KiB must be stripped.
> +
> +The ``barebox_update`` command takes care of this and need just be
> +supplied a barebox image as argument.
-- 
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