[U-Boot] [PATCH v4 0/6] Enable Thumb build for ARM platforms

Allen Martin
2012-04-03T22:48:36Z

> Tom, Albert,
>
> Does this series look good?

Hi Aneesh,

The assembly files (like arch/arm/cpu/armv7/start.S) are still compiled ARM 32 with this patch series, but they call into C files that are compiled -mthumb. Shouldn't the branches be changed into thumb state changing branches (bx/blx) ? In particular I'm looking at the call into board_init_f()

-Allen

>
> On Thursday 08 March 2012 10:50 PM, Aneesh V wrote:
> > Thumb is an alternate instruction set available in many
> > ARM processors. Below is a detailed description from ARM
> > specs:
> >
> > "The Thumb instruction set is a re-encoded subset of the
> > ARM instruction set. Thumb instructions execute in their
> > own processor state, with the architecture defining the
> > mechanisms required to transition between ARM and Thumb
> > states. The key difference is that Thumb instructions are
> > half the size of ARM instructions(16 bits compared with 32
> > bits). Greater code density can usually be achieved by using
> > the Thumb instruction set in preference to the ARM instruction
> > set, at a cost of some reduction in performance"
> >
> > "In ARMv6T2, Thumb-2 technology is introduced. This technology
> > makes it possible to extend the original Thumb instruction set
> > with many 32-bit instructions. The range of 32-bit Thumb instructions
> > included in ARMv6T2 permits Thumb code to achieve performance
> > similar to ARM code, with code density better than that of earlier
> > Thumb code. From ARMv6T2, the ARM and Thumb instruction sets provide
> > almost identical functionality"
> >
> > This series adds Thumb support in U-Boot and enables it for
> > OMAP4. It also fixes issues faced while booting OMAP4 with
> > Thumb-2 images of U-Boot and SPL.
> >
> > Thumb mode is becoming increasingly relevant for U-Boot with
> > the advent of SPL. It's very important to keep SPL size smaller
> > considering the internal RAM size constraints on many platforms.
> > On OMAP4 the size reduction enables us to use SPL on secure devices
> > that have smaller internal RAM available for non-secure world.
> >
> > To enable support for new platforms you just need to add
> > CONFIG_SYS_THUMB_BUILD in your config file.
> >
> > Tool-chains tried:
> > 1. Sourcery G++ Lite 2010q1-202
> > arm-none-linux-gnueabi-gcc (Sourcery G++ Lite 2010q1-202) 4.4.1
> > GNU ld (Sourcery G++ Lite 2010q1-202) - binutils 2.19.51.20090709
> >
> > 2. Linaro 4.6-2012.01
> > arm-linux-gnueabi-gcc (crosstool-NG linaro-1.13.1-2012.01-20120125 -
> > Linaro GCC 2012.01) 4.6.3 20120105 (prerelease)
> > GNU ld (crosstool-NG linaro-1.13.1-2012.01-20120125 - Linaro GCC
> 2012.01) 2.22
> >
> > Code-size reduction:
> > Image ARM build Thumb build % Reduction
> > u-boot.bin 190408 144676 24.01%
> > u-boot-spl.bin 33200 25096 24.40%
> >
> > Performance(timestamp just before the main loop):
> > ARM build Thumb build % Reduction
> > 898510us 878247us -2.25%
> >
> > Performance actually improved marginally for the Thumb
> > build, maybe because of the reduced image sizes.
> >
> > Aneesh V (6):
> > arm: adapt asm/linkage.h from Linux
> > armv7: add appropriate headers for assembly functions
> > ARM: enable Thumb build
> > armv7: Use -march=armv7-a and thereby enable Thumb-2
> > omap4+: Avoid using __attribute__ ((__packed__))
> > OMAP4: enable Thumb build
> >
> > README | 8 +++++
> > arch/arm/config.mk | 22 +++++++++----
> > arch/arm/cpu/armv7/config.mk | 7 +++-
> > arch/arm/cpu/armv7/mx5/lowlevel_init.S | 5 ++-
> > arch/arm/cpu/armv7/mx6/lowlevel_init.S | 5 ++-
> > arch/arm/cpu/armv7/omap-common/lowlevel_init.S | 14 ++++----
> > arch/arm/cpu/armv7/omap-common/reset.S | 5 ++-
> > arch/arm/cpu/armv7/omap3/lowlevel_init.S | 41 ++++++++++++--
> ---------
> > arch/arm/cpu/armv7/s5pc1xx/cache.S | 10 +++--
> > arch/arm/cpu/armv7/s5pc1xx/reset.S | 5 ++-
> > arch/arm/cpu/armv7/start.S | 13 ++++---
> > arch/arm/cpu/armv7/tegra2/lowlevel_init.S | 5 ++-
> > arch/arm/cpu/armv7/u8500/lowlevel.S | 9 +++--
> > arch/arm/include/asm/arch-omap4/mux_omap4.h | 2 +-
> > arch/arm/include/asm/arch-omap5/mux_omap5.h | 2 +-
> > arch/arm/include/asm/linkage.h | 7 ++++
> > include/configs/omap4_common.h | 2 +
> > include/linux/linkage.h | 7 +++-
> > 18 files changed, 106 insertions(+), 63 deletions(-)
> > create mode 100644 arch/arm/include/asm/linkage.h
> >
>
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot

nvpublic