[U-Boot] i.MX SPL tools (was Re: [RFC PATCH 00/12] imx: mx6: add virtual mx6memcal board)

[Eric Nelson <eric@nelint.com>]

On 06/21/2016 11:41 AM, Eric Nelson wrote:
> This patch set makes use of the dynamic DDR calibration routines added in commit
> d339f16 to define an alternative to the Freescale DDR stress tester tool.
> 
Hi all,

While preparing this patch set, I thought again about the tools we have
for managing SPL images, and especially "first boot" issues (when a
full U-Boot isn't available or isn't programmed into the normal boot
device).

Since the "mx6memcal" device is deliberately small, with only
the DDR and UART defined, there's no way to load a full U-Boot
and doing so would defeat the primary purpose.

We've discussed this at length on a number of occasions, (most recently
in [5]) but I don't think we have a good solution.

I just looked at Troy's ancient patches ([1] and [2]) and it seems that
these two patches are the bulk of the work needed to build a combined
SPL+U-Boot image, and if I understand patch 2 correctly, SPL could
tell at run-time that it was executed via a plugin and return control
to the Boot ROM instead of trying to load U-Boot or a kernel.

If I recall correctly, Troy dropped these patches because of push-back
that came from the sheer size of the 21-patch set, and not because of
any particular objection to support for plugins.

It seems that a little work here would remove the need for things
like Stefano's patch in [3] or Michael thoughts of adding DFU support
in [4].

I'm interested in hearing your thoughts on the subject.

Regards,


Eric

[1] [U-Boot,V2,06/21] imximage: add plugin commands
	https://patchwork.ozlabs.org/patch/186051/
[2] [U-Boot,V2,08/21] mx6: add plugin file for use with imximage.cfg
	https://patchwork.ozlabs.org/patch/186054/
[3] [U-Boot] [PATCH v2] imx_common: check for Serial Downloader in
spl_boot_device
	http://lists.denx.de/pipermail/u-boot/2015-December/237555.html
[4] Discussion of SPU and DFU
	http://lists.denx.de/pipermail/u-boot/2013-October/thread.html#165805
[5] Discussion of booting Wand through USB
	http://lists.denx.de/pipermail/u-boot/2015-May/thread.html#215573