[U-Boot] Unified u-boot feature set for simpler distro support

[Stephen Warren <swarren@wwwdotorg.org>]

On 08/05/2013 03:00 PM, Tom Rini wrote:
> On Mon, Aug 05, 2013 at 02:49:58PM -0600, Stephen Warren wrote:
>> On 08/05/2013 02:43 PM, Wolfgang Denk wrote: ...
>>> Please look into Tom's proposal to got the SPL / Falcon mode
>>> way. I fully agre with him there.
>> 
>> From my reading of doc/README.falcon, in order to use it, you
>> still must set everything up in order to do a full non-falcon
>> boot, and then simply save a serialized version of the
>> zImage/DTB/bootargs/... using a special U-Boot command.
> 
> You must setup a certain amount of things, yes.  And from what
> you've documented in the i2c thread about the Tegra orer, it
> depends a bit on the SoC.
> 
> [snip]
>> And also, if a distro installs an updated kernel, how does it
>> tell U-Boot to invalidate the previously serialized data that
>> falcon mode uses to boot, and re-create it using the new kernel
>> image?
> 
> Dirty "secret" time, with device trees, it's just the device tree
> we loaded, with whatever run-time fixups are done.  Doing this from
> the Linux side is a solvable problem.

Oh! Where does the zImage binary come from then? The documentation
explicitly says it's written to flash by "spl export", and I assume
that's so that the SPL (that's executing falcon mode) doesn't have to
initialize SD card drivers, filesystems, etc. in order to load the
zImage from the card, but rather simply a single flash driver to read
the exported image. If falcon mode has to do all that, why is it any
faster than the main U-Boot doing exactly the same?