[PATCH] CAS DFP support

[Kumar Gala]

On Nov 22, 2006, at 10:06 AM, Peter Bergner wrote:

> On Wed, 2006-11-22 at 09:46 -0600, Kumar Gala wrote:
>> On Nov 22, 2006, at 9:20 AM, Jake Moilanen wrote:
>>
>>> When booting a Power6 in compat mode, the DFP bit must be set in the
>>> client architecture call, or else firmware will downgrade the
>>> compliance
>>> to P5 compat mode, thus removing VMX and DFP instructions.
>>>
>>> Signed-off-by: Jake Moilanen <moilanen at austin.ibm.com>
>>>
>>> --- 2.6/arch/powerpc/kernel/prom_init.c~	2006-11-13  
>>> 15:01:13.000000000
>>> -0600
>>> +++ 2.6/arch/powerpc/kernel/prom_init.c	2006-11-21  
>>> 18:38:27.000000000
>>> -0600
>>> @@ -627,6 +627,7 @@ static void __init early_cmdline_parse(v
>>>  /* Option vector 3: processor options supported */
>>>  #define OV3_FP			0x80	/* floating point */
>>>  #define OV3_VMX			0x40	/* VMX/Altivec */
>>> +#define OV3_DFP			0x20	/* decimal floating point */
>>
>> Can we make the flag OV3_DECFP to distinguish it from Double FP.
>
> One thing OV3_DFP has going for it is that is matches the nomenclature
> used by GCC, binutils.  I'm not sure what you mean by Double FP,  
> unless
> you're referring to the double wide FP unit on the Blue Gene/L 440
> processor, but they don't refer to it as Double FP.

I'm referring to plain old double precision floating point.  The e500  
core from Freescale has version that provide embedded single  
precision floating point (EFP_SINGLE) and versions that provide both  
embedded double precision floating point (EFP_DOUBLE).  I just want  
use to be clear the DFP could mean either double or decimal as far as  
I'm concerned.

Also, I think the 602 (may have never seen the light of day) only  
implemented single precision floating point.

- k