[U-Boot] Whose responsibility is it to enable FPU?

Måns Rullgård mans at mansr.com
Mon Jun 14 22:10:15 CEST 2010


gnemas at gmail.com writes:

> I built u-boot for a 440EPx board derived from the sequoia configuration.
>
> I am using an FPU-enabled gcc cross compiler.
>
> U-Boot runs fine and successfully boots my operating system (Linux and
> uClibc-based root filesystem).
>
> However, I was having a problem running busybox that I traced to
> errors  occurring executing setjmp, which attempts to save floating
> point registers.
>
> Then I realized that the FPU was not enabled in the MSR or in the ccr0
> register.
>
> Have I misconfigured something, or should I go ahead and add code to
> u-boot  to enable the FPU?

It is generally the responsibility of the kernel to enable the FPU for
tasks which require it, allowing lazy save/restore of the FPU state on
context switching.  Enabling the FPU in u-boot might interfere with this.

-- 
Måns Rullgård
mans at mansr.com



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