[U-Boot] CONFIG_REVISION (was i.MX6: mx6qsabrelite: allow use with Freescale 2.6.38 kernels)

[Eric Nelson]

On 03/04/2012 04:09 AM, Stefano Babic wrote:
> On 03/03/2012 14:30, Wolfgang Denk wrote:
>> Dear Dirk Behme,
>>
>> <snip>
>>
>> There are 3 commits in this series:
>>
>> [PATCH 1/3] i.MX6: mx6qsabrelite: add CONFIG_REVISION_TAG
>> [PATCH 2/3] i.MX6: mx6qsabrelite: add MACH_TYPE_MX6Q_SABRELITE
>> [PATCH 3/3] i.MX6: mx6qsabrelite: add ext2 support
>>
>> I dislike #1 because it uses the completely undocumented
>> CONFIG_REVISION_TAG, and I agree with Marek's and Stefano's comments.
>
> A lot of boards are currently set CONFIG_REVISION_TAG. Sure, it would be
> nice to document it. To be consistent we should drop this CONFIG_ from
> all boards, or add documentation for it.
>
> However, I am asking if this TAG is really needed. I have searched in
> 2.6.38 Kernel provided by Freescale if the TAG is really evaluated to
> set different revisions of the boards, but I have not found anything. Is
> it  really needed ? If not, we should drop it.
>

The linkage is really indirect. The ATAG item is still supported in the
main-line kernel for ARM:
	http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=blob;f=arch/arm/kernel/setup.c;h=a255c39612ca3cfa10bddb7c7728216efeeb04d5;hb=HEAD#l704

The breakage I noticed was in the VPU driver, which refused to load
with a zero-value in system_rev. The net result was no video playback
in the Freescale Android ICS release.