[U-Boot] [PATCH 1/2] tegra2: Always build with USE_PRIVATE_LIBGCC=yes.

[Stephen Warren <swarren@nvidia.com>]

On 01/05/2012 08:50 AM, Wolfgang Denk wrote:
> Dear Thierry Reding,
> 
> In message <1321524246-5187-2-git-send-email-thierry.reding@avionic-design.de> you wrote:
>> The AVP on Tegra2 doesn't boot properly when U-Boot is linked against
>> the GCC provided libgcc. To work around this, always build and link
>> against a private libgcc for Tegra2-based boards.
> 
> I notice this patch only now, when pulling in from u-boot-arm.
> 
> I will accept this only temporarily.  Why don't you use a working tool
> chain instead, or fix the one you are using?

I believe the issue isn't that the toolchain is broken, but due to the
mix of multiple CPU types on Tegra, all of which run the same U-Boot binary.

U-Boot starts execution on the AVP CPU, an ARMv4(?) CPU. U-Boot then
inits the main CPUs, ARMv7 Cortex A9s, and arranges for them to continue
running U-Boot.

The libraries included in the toolchain are built for the ARMv7 CPUs,
and hence fail to operate correctly when used by the portion of U-Boot
which runs on the ARMv4 CPU, presumably due to ISA differences. IIRC,
there are overrides in the U-Boot build process such that some/all of
U-Boot is built so it'll run on ARMv4 OK, which is why using libgcc
built by U-Boot solves this.

-- 
nvpublic