[U-Boot] [RFC PATCH 1/2] armv7: enable Thumb build for armv7

[Loïc Minier]

On Tue, Mar 15, 2011, Aneesh V wrote:
> Please note that I am enabling armv7-a in the second patch in omap4
> config.mk file. The reason I didn't do this here was some ARMv7 SoCs do
> not want to use -march=armv7-a even if the compiler supports it. Tegra2
> is an example. Please see the below from Tegra2 config.mk:
> 
> # Use ARMv4 for Tegra2 - initial code runs on the AVP, which is an ARM7TDI.
> PLATFORM_CPPFLAGS += -march=armv4

 Good point, I wonder whether it would make sense to have
 arch/arm/cpu/armv7/config.mk default to -march=armv7 and Tegra2 to
 override this with -march=armv4.  Maybe this code doesn't belong under
 armv7 though; or perhaps -march=armv4 should only be set when building
 a subset of the files rather than by default.

> This being the case I would have had to define another CONFIG flag if I
> had to add -march=armv7-a in arch/arm/cpu/armv7/config.mk. I thought it
> un-necessary and instead put it in the SoC specific file. So, Tegra2
> can continue to use -march=armv4 and will get Thumb-1 if they enable
> CONFIG_SYS_THUMB_BUILD. Or do you think we should define something like
> CONFIG_SYS_MARCH_ARMV7

 Up to you, but I would expect that code udner arch/arm/cpu/armv7/ would
 build with -march=armv7 (maybe not -a though), with specific overrides
 where that's not the case; it would feel a bit odd to me to have this
 as a "config" option.

-- 
Loïc Minier