ppc4xx simple vs SoC's

ppc4xx simple vs SoC's

[Benjamin Herrenschmidt]

Hi Josh !

I was helping Tony with some of the Currituck stuff when I noticed an
oddity...

So we have various "SoC" config symbols such as 440EP, 460SX, etc...
that in turn select various bits & pieces that enable support for that
SoC (such as EMAC4 support or FPU support). Those only act as "enables"
for compiling of the code, there is still going to be a runtime check of
course.

Those SoC config symbols are not user selectable, they are meant to be
themselves select'ed by the board Kconfig entries.

However, the entry for ppc44x_simple doesn't select any of these,
meaning for example, AFAIK, that you don't get EMAC4 etc... I'm
surprised things work at all !

What am I missing ?

Cheers,
Ben.

Re: ppc4xx simple vs SoC's

[Josh Boyer]

On Thu, Dec 1, 2011 at 12:39 AM, Benjamin Herrenschmidt
<benh@kernel.crashing.org> wrote:
> Hi Josh !
>
> I was helping Tony with some of the Currituck stuff when I noticed an
> oddity...
>
> So we have various "SoC" config symbols such as 440EP, 460SX, etc...
> that in turn select various bits & pieces that enable support for that
> SoC (such as EMAC4 support or FPU support). Those only act as "enables"
> for compiling of the code, there is still going to be a runtime check of
> course.
>
> Those SoC config symbols are not user selectable, they are meant to be
> themselves select'ed by the board Kconfig entries.

Yep, and they are.

> However, the entry for ppc44x_simple doesn't select any of these,
> meaning for example, AFAIK, that you don't get EMAC4 etc... I'm
> surprised things work at all !
>
> What am I missing ?

CONFIG_PPC44x_SIMPLE is selected by the board Kconfig values, which
also select all of the SoC Kconfig options they need as well.
ppc44x_simple started as a way to basically avoid duplicating a bunch
of board.c files, but it's still "driven" from the board options.

So hopefully that explains how things are working today.  The question
now is whether you would like something different?

josh

Re: ppc4xx simple vs SoC's

[Benjamin Herrenschmidt]

On Thu, 2011-12-01 at 06:44 -0500, Josh Boyer wrote:

> > However, the entry for ppc44x_simple doesn't select any of these,
> > meaning for example, AFAIK, that you don't get EMAC4 etc... I'm
> > surprised things work at all !
> >
> > What am I missing ?
> 
> CONFIG_PPC44x_SIMPLE is selected by the board Kconfig values, which
> also select all of the SoC Kconfig options they need as well.
> ppc44x_simple started as a way to basically avoid duplicating a bunch
> of board.c files, but it's still "driven" from the board options.
> 
> So hopefully that explains how things are working today.  The question
> now is whether you would like something different?

Ok, just getting my head around that stuff, I haven't really looked
since you and Grant I believe came up with the scheme :-) (Was wondering
what to do for currituck, but for now we'll keep it a separate board, at
least until I can decide how to deal with the interrupt quirk).

I just hadn't realized that while we had ppc4xx_simple, we still had
board Kconfig's to enable it.

Cheers,
Ben.