[Cbe-oss-dev] [RFC, PATCH] selection of CPU optimization

[Kumar Gala]

On Apr 12, 2007, at 12:26 PM, Arnd Bergmann wrote:

> On Thursday 12 April 2007, Kumar Gala wrote:
>
>>> +config PPC_CPU_ANY32
>>> +	bool "Generic 32 bit PowerPC"
>>> +	depends on PPC_6xx || PPC_8xx || 4xx || E200 || E500
>>> +	select PPC_ENABLE_ALTIVEC
>>
>> What is PPC_ENABLE_ALTIVEC used for?
>
> The idea was that PPC_ENABLE_ALTIVEC is selected when PPC_ALTIVEC
> _can_ be enabled, while PPC_ALTIVEC is selected by some CPUs
> directly.

Ok, seems like 8xx/4xx/e200/e500 its clear will NEVER have Altivec.   
I think we should put the PPC_ENABLE_ALTIVEC on PPC_6xx which should  
cover all the reasonable possible cases (603, 604, 7xx).

> I now remember that I had not done this part right in the patch
> I posted. The correct behavior should be something like
>
> choice
> 	prompt "Processor level"
>
> config PPC_CPU_740
> 	bool "G3 or higher"
> 	select PPC_ENABLE_ALTIVEC
> 	# altivec is possible
>
> config PPC_CPU_86xx
> 	bool "86xx"
> 	select PPC_ALTIVEC
> 	# altivec is required
>
> config PPC_CPU_4xx
> 	bool "4xx"
> 	# altivec is not possible
>
> endchoice
>
> config PPC_ENABLE_ALTIVEC
> 	bool
>
> config PPC_ALTIVEC
> 	bool "Enable the use of Altivec"
> 	depends on PPC_ENABLE_ALTIVEC
>
> I'll fix this up in the next version, which should also
> be split into simpler patches.
>
>>> +config PPC_CPU_FLAG
>>> +	string
>>> +	default "" if PPC_CPU_UNSPECIFIED
>>> +	default "-mcpu=powerpc64" if PPC_CPU_ANY64
>>> +	default "-mcpu=rs64" if PPC_CPU_RS64
>>> +	default "-mcpu=power3" if PPC_CPU_POWER3
>>> +	default "-mcpu=power4" if PPC_CPU_POWER4
>>> +	default "-mcpu=power5" if PPC_CPU_POWER5
>>> +	default "-mcpu=power5+" if PPC_CPU_POWER5PLUS
>>> +	default "-mcpu=power6" if PPC_CPU_POWER6
>>> +	default "-mcpu=970" if PPC_CPU_970
>>> +	default "" if PPC_CPU_CELLBE
>>> +	default "" if PPC_CPU_PA6T
>>> +	default "-mcpu=powerpc" if PPC_CPU_ANY32
>>> +	default "-mcpu=601" if PPC_CPU_601
>>> +	default "-mcpu=603" if PPC_CPU_603
>>> +	default "-mcpu=604" if PPC_CPU_604
>>> +	default "-mcpu=750" if PPC_CPU_750
>>> +	default "-mcpu=7400" if PPC_CPU_7400
>>> +	default "-mcpu=7450" if PPC_CPU_7450
>>> +	default "-mcpu=801" if PPC_CPU_801
>>> +	default "-mcpu=821" if PPC_CPU_821
>>> +	default "-mcpu=823" if PPC_CPU_823
>>> +	default "-mcpu=860" if PPC_CPU_860
>>> +	default "-mcpu=403" if PPC_CPU_403
>>> +	default "-mcpu=405" if PPC_CPU_405
>>> +	default "-mcpu=440" if PPC_CPU_440
>>> +	default "" if PPC_CPU_E200
>>> +	default "" if PPC_CPU_E500
>>
>> I think -mcpu=8540 will work for e500 (same for tune)
>
> Interestingly, -mcpu=8540 is known to gcc, according to
> gcc-4.0.3 -dumpspecs, but is not listed in the documentation.
> There is also -me500, while -me200 seems to be known only
> to gas but not gcc.
>
> What would be the right options to pass on e200 and on
> pa6t?

I think leaving it blank is the right thing for e200.

Olof should know what pa6t needs or what makes sense for it.

>>> +config PPC_OF_PLATFORM_PCI
>>> +	bool
>>> +	depends on PPC64 # not supported on 32 bits yet
>>> +	default n
>>
>> Should this really be in here? I don't see how OF PCI has anything to
>> do with CPU/core.
>
> Right.
>
> 	Arnd <><