[U-Boot] [PATCH v2] arm: support Thumb-1 with CONFIG_SYS_THUMB_BUILD

[Albert ARIBAUD]

Hello Stefan,

On Thu, 09 Apr 2015 11:22:27 +0200, Stefan Roese <sr at denx.de> wrote:
> Hi Albert,
> 
> On 25.02.2015 23:09, Albert ARIBAUD wrote:
> > On Tue, 24 Feb 2015 14:53:36 +0100, Albert ARIBAUD
> > <albert.u.boot at aribaud.net> wrote:
> >> When building a THumb-1-only target with CONFIG_SYS_THUMB_BUILD,
> >> some files fail to build, most of the time because they include
> >> mcr instructions, which only exist for Thumb-2.
> >>
> >> Thos patch introduces a Kconfig option CONFIG_THUMB2 and uses
> >> it to select between Thumb-2 and ARM mode for the aforementioned
> >> files.
> >>
> >> Signed-off-by: Albert ARIBAUD <albert.u.boot at aribaud.net>
> >> ---
> >> This patch has been build-tested and run-tested on ED Mini V2,
> >> above the "edmini: switch to SPL" patch, and found to reduce
> >> U-Boot size by 25% and SPL size by 14%... and to run fine. :)
> >>
> >> This patch has also been tested against side effects on the
> >> non-Thumb wireless_space target. The binaries produced with
> >> and without ths patch were found to differ only by their
> >> version string.
> >>
> >> Changes in v2:
> >> - fixed a typo in the commit message
> >> - added file arch/arm/thumb1/include/asm/proc-armv/system.h,
> >>    which overrides arch/arm/include/asm/proc-armv/system.h
> >>    when building for Thumb-1 and provides non-functional but
> >>    Thumb-compilable IRQ and FIQ related macros and functions.
> >
> > Ok, this does not fare as good as I have hoped, because there are also
> > thumb1-unfrendly macros in arch/arm/include/asm/cache.h, this time with
> > mcr and mrc instructions.
> >
> > /me hates macros used as inline functions. :(
> >
> > I cannot just replace the macros with empty inline functions as I did
> > with arch/arm/include/asm/proc-armv/system.h, since this would cause
> > cache to not work. :(
> >
> > This leaves only one solution: when buildding for thumb1, replace the
> > macros in cache.h with plain function prototypes, and provide simple
> > ARM-state implementations for these. We'll lose a bit of performance as
> > instead of a single mcr or mrc instruction, we'll have a call switching
> > from Thumb to ARM state, the mcr/mrc instruction, and a return to Thumb
> > state. Hopefully that won't hurt performance too much.
> >
> > V3 in the works.
> 
> Any update on this?

I am just restarting on this right now.

> Thanks,
> Stefan

Amicalement,
-- 
Albert.