[PATCH] doc: imx: psb: Document usage of SRC_GPR10 PERSIST_SECONDARY_BOOT for A/B switching

[sbabic at denx.de]

> Document SRC_GPR10 PERSIST_SECONDARY_BOOT functionality. This is useful for
> reliable bootloader A/B updates, as it permits switching between two copies
> of bootloader at different offsets of the same storage. The switch happens
> in case one copy is corrupted OR can be enforced by user. This functionality
> is present at least since i.MX53, however is poorly documented in all known
> SoC datasheets, hence this document aims to clarify the usage, currently on
> i.MX7D and i.MX8MM.
> Signed-off-by: Marek Vasut <marex at denx.de> # Original MX7D work, this document
> Signed-off-by: Igor Opaniuk <igor.opaniuk at foundries.io> # All the MX8M work
> Cc: Christoph Niedermaier <cniedermaier at dh-electronics.de>
> Cc: Fabio Estevam <festevam at gmail.com>
> Cc: Harald Seiler <hws at denx.de>
> Cc: Igor Opaniuk <igor.opaniuk at foundries.io>
> Cc: Jan Kiszka <jan.kiszka at siemens.com>
> Cc: Ludwig Zenz <lzenz at dh-electronics.com>
> Cc: Marcel Ziswiler <marcel.ziswiler at toradex.com>
> Cc: Peng Fan <peng.fan at nxp.com>
> Cc: Stefano Babic <sbabic at denx.de>
> Cc: Ye Li <ye.li at nxp.com>
> Cc: uboot-imx <uboot-imx at nxp.com>
> Reviewed-by: Peng Fan <peng.fan at nxp.com>
Applied to u-boot-imx, master, thanks !

Best regards,
Stefano Babic

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