Endianness versus too many byte swaps??

[Kumar Gala]

On Mar 5, 2007, at 9:02 AM, Charles Krinke wrote:

>
>
> You do understand that readl is in fact a call to in_le32() on ppc
> (cf. include/asm-ppc/io.h).
>
> The question now is, what endianness you would like in that register?
>
> Regards
> --  
> Stephane
>
> Dear Stephane:
>
> Your point is well made. I can see that readl is in fact a call to
> in_le32. Maybe there is a more basic problem here.
>
> If I change the call to readl to a call to in_be32, things make sense
> again. So, maybe I don't quite understand the endianness setup of this
> Linux project.

readl/writel are for PCI bus accesses.  PCI is inherently little endian.

> I am told that we are running this ppc in big endian, so would this  
> mean
> that readl & writel should actually be resolving to in_be32/out_be32
> respectively? Is there some other setup that may be wrong?

Nope, readl/writel are doing the write thing, they will ALWAYS be  
little endian.

You truly want in_be*/out_be* when accessing 85xx CCSR registers  
since all of them are big endian.

- k