[U-Boot] [PATCH v2 3/5] MIPS: Optimize the setup of endianess and CPU optimization flags

[Daniel Schwierzeck]

Hi Shinya,

2011/3/17 Shinya Kuribayashi <skuribay at pobox.com>:
> On 03/16/2011 11:41 PM, Daniel Schwierzeck wrote:
>> Is my approach with -march acceptable? This is more important to me
>> for supporting new SoCs with 24k and 34k CPU cores. I think its a
>> clean approach to use a default Mips32 architecture optimization plus
>> a per CPU optimization configured in the SoC directories.
>
> IIUC this is a binutils related issue.
>
>> @@ -20,20 +20,13 @@
>>  # Foundation, Inc., 59 Temple Place, Suite 330, Boston,
>>  # MA 02111-1307 USA
>>  #
>> -v=$(shell $(AS) --version | grep 'GNU assembler' | egrep -o '2\.[0-9\.]+' | cut -d. -f2)
>> -MIPSFLAGS:=$(shell \
>> -if [ "$v" -lt "14" ]; then \
>> -     echo "-mcpu=4kc"; \
>> -else \
>> -     echo "-march=4kc -mtune=4kc"; \
>> -fi)
>>
>> [...]
>> +# Optimization flags for all Mips32 CPUs
>> +MIPSFLAGS = $(call cc-option,-march=mips32r2,-mips32r2 -Wa,-mips32r2)
>
> According to GNU gas NEWS, mips32r2 support was introduced in 2.14:
>
> http://sourceware.org/cgi-bin/cvsweb.cgi/~checkout~/src/gas/NEWS?rev=1.117&content-type=text/plain&cvsroot=src&only_with_tag=binutils-binutils-2_21
>
> On the other hand, we have a number of the ELDK releases so far, and
> their binutils versions vary from 2.11 (ELDK2.1.0) to 2.16.1 (ELDK4.1).
>
> 2.1.0: http://mirror.switch.ch/ftp/mirror/eldk/2.1.0/eldk-mips-linux-x86/README.html
> 3.0:   (N/A for MIPS?)
> 3.1:   http://mirror.switch.ch/ftp/mirror/eldk/3.1/mips-linux-x86/distribution/README.html
> 3.1.1: http://mirror.switch.ch/ftp/mirror/eldk/3.1.1/mips-linux-x86/distribution/README.html
> 4.0:   http://mirror.switch.ch/ftp/mirror/eldk/4.0/mips-linux-x86/distribution/README.html
>       http://www.denx.de/en/News/PressReleaseELDK40
> 4.1:   http://mirror.switch.ch/ftp/mirror/eldk/4.1/mips-linux-x86/distribution/README.html
>       http://www.denx.de/en/News/PressReleaseELDK41
> 4.2:   (N/A for MIPS?)
>
> Does above change break any builds with older binutils?  Personally, I'm
> ok with dropping older toolchains to some extent.  However, if it breaks
> builds with older toolchains, strictly speaking older versions of the
> ELDK releases, the decision is up to Wolfgang.

I did some researching and testing with ELDK-4.1, ELDK-4.0 and ELDK-3.1.1.

In ELDK-3.1.1 we have:
- mips_4KC-gcc (GCC) 3.3.3 (DENX ELDK 3.1.1 3.3.3-9)
- GNU assembler 2.14 20030612

Therefore mips32r2 is already supported. But there is another problem with this
binutils version. The latest additions to mips.lds and u-boot.lds for
supporting recent
binutils are causing parse errors. Thus ELDK-3.1.1 and earlier are not
functional with
mainline U-Boot anyway. ELDK-4.0 and 4.1 with gcc-4.0.0 and
binutils-2.16.1 are working
properly.

I suggest to drop official support for ELDK-3.1.1 / binutils-2.14 and earlier.


Best regards
Daniel