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

[Aneesh V <aneesh@ti.com>]

Tom, Albert,

Does this series look good?

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
>