Re: [microblaze-uclinux] Compilation problem when hardware multipler turned off

[John Williams <jwilliams@xxxxxxxxxxxxxx>]

Hi Kevin,

Kevin Chen wrote:

> Does anyone see compilation CFLAG problem when Microblaze hard 
> multiplier is turned off?

What's the error message from GCC?

> The CFLAG still use the option for hard multipler.

The logic in config.arch and Rules.mak in intended to reflect that 
MicroBlaze automatically uses HW multipler on V2, V4 and S3 families.

It also sets it if the USE_HW_MUL option is set on the CPU.

This is a mess, and we've cleaned up for the next petalinux release.

> I’ve attached the fix. The files’ path follow
>
> petalinux-dist/linux-2.4.x/arch/microblaze/platform/Rules.make
>
> petalinux-dist/vendors/config/microblaze/config.arch

>  Any comment or other way to fix?

The concern I have with your change is that, in my understanding and 
experience, with MicroBlaze v4.00 at least, EDK ignores you if you set 
USE_HW_MUL=0 in the MHS file, if targetting a multiplier-capable FPGA 
family.

I don't remember seeing anywhere on a single page, a complete overview 
of HW multiplier instantiation logic for the full range of FPGA families 
and CPU versions, with and without the USE_HW_MUL parameter.  If you can 
find such a thing, let me know and we'll fix the Makefile rules to obey 
it! :)

Thanks,

John
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