[PATCH RFC] rockchip: add /chosen/bootsource to U-Boot proper DT

[Tom Rini]

On Wed, Jul 30, 2025 at 02:03:18PM +0200, Quentin Schulz wrote:

> From: Quentin Schulz <quentin.schulz at cherry.de>
> 
> U-Boot typically can be loaded from different storage media, such as
> eMMC, SD card, SPI flash, but also from non-persistent media such as USB
> (via proprietary protocols loading directly into SRAM, or fastboot, DFU,
>  etc..), JTAG, ...
> 
> This information is usually reported by the BootROM via some proprietary
> mechanism (some specific address in registers/DRAM for example). For
> Rockchip, that information is stored in a register
> (BROM_BOOTSOURCE_ID_ADDR).
> 
> While we already have the information about which medium was used to
> load U-Boot proper from SPL (via /chosen/u-boot,spl-boot-device), this
> new property represents the medium used to load U-Boot first phase
> (depending on configuration, can be VPL/TPL/SPL) which absolutely may
> differ from the one used to load U-Boot proper!
> 
> It would be useful to know which medium was used to load the first phase
> of U-Boot, for example to check fallback mechanisms (proper loaded from
> a different medium than first phase) are actually working.
> 
> For now, this only applies to Rockchip's U-Boot proper DT but could be
> applied to the kernel's as well and possibly for other architectures or
> vendors.
> 
> Signed-off-by: Quentin Schulz <quentin.schulz at cherry.de>
> ---
> I have a board (RK3399 Puma) running U-Boot which currently has 9 boot
> scenarios (eMMC/SD/SPI-NOR for the first phase, eMMC/SD/SPI-NOR for the
> next phases; not counting USB loading yet, which would make it a few
> more). I cannot force the BootROM of this board to select a specific
> device aside from erasing the other media.
> 
> The only way to identify which device was used for the first phase is to
> parse U-Boot first phase console output or add some custom logic for my
> board. To validate that a new version of the bootloader works, including
> the fallback mechanisms, I need to make sure the BootROM loads the first
> phase from the expected device otherwise I may have false positives.
> This would be useful for automated testing.
> 
> Patches pending in the devicetree-spec[1] and dt-schema[2], hence the
> RFC here.
> 
> [1] https://lore.kernel.org/devicetree-spec/20250505-bootsource-v2-1-5a315d9bff26@cherry.de/
> [2] https://github.com/devicetree-org/dt-schema/pull/169

I am conceptually fine with the changes, but this needs to have the
schema side approved first, just for the record.

-- 
Tom
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