[U-Boot] [PATCH v4 5/8] omap-common: SYS_BOOT-based fallback boot device selection for peripheral boot

[Tom Rini]

On Thu, Jul 02, 2015 at 12:19:41AM +0200, Paul Kocialkowski wrote:

> OMAP devices might boot from peripheral devices, such as UART or USB.
> When that happens, the U-Boot SPL tries to boot the next stage (complete U-Boot)
> from that peripheral device, but in most cases, this is not a valid boot device.
> 
> This introduces a fallback option that reads the SYS_BOOT pins, that are used by
> the bootrom to determine which device to boot from. It is intended for the
> SYS_BOOT value to be interpreted in the memory-preferred scheme, so that the
> U-Boot SPL can load the next stage from a valid location.
> 
> Practically, this options allows loading the U-Boot SPL through USB and have it
> load the next stage according to the memory device selected by SYS_BOOT instead
> of stalling.

Can you elaborate on this more please?  The normal flow is that you load
SPL via UART and then load U-Boot via UART, or SPL via USB RNDIS and
then U-Boot via USB RNDIS.  It sounds like you're changing things so
that you load first via UART and then via say SD (or whatever the pins
would be set for) unless you have the bits enabled for loading the next
stage via that peripheral, which is the default case.

Now, I know you didn't do this just for fun, so what's the use case you
have here exactly?  Thanks!

-- 
Tom
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