Re: [PATCHv3 1/3] net: fec: do not use readl()/writel() for ColdFire

[Jakub Kicinski]

On Fri, 11 Sep 2026 23:03:56 +1000 Greg Ungerer wrote:
> On 11/9/26 10:42, Jakub Kicinski wrote:
> > On Mon,  7 Sep 2026 23:37:09 +1000 Greg Ungerer wrote:  
> >> The FEC driver works today because the m68k architecture io.h has a
> >> kludge in the definitions of the readl() and writel() functions for
> >> ColdFire that allow big-endian access if the address of the register to
> >> access is within the SoC's internal peripheral registers. This is being
> >> fixed in the near future to define readl() and writel() correctly - with
> >> no byte swapping. Thus the motivation for this fix here.  
> > 
> > What is the motivation for this cleanup?  
> 
> Sorry, maybe you were not in the CC list of the cover email. From that:
> 
>   This collection of patches is aimed at fixing the non-standard ColdFire
>   set of readX()/writeX() IO access functions. Instead switching to using the
>   asm-generic definitions in include/asm-generic/io.h. The difficulty comes
>   in trying not to break any drivers with this change.
> 
>   The implementation of the readX()/writeX() family of IO access functions
>   is non-standard on ColdFire platforms. They either return big-endian (that
>   is native endian) data, or on platforms with PCI bus support check the
>   supplied address and return either big or little endian data based on that
>   check. This is non-standard, they are expected to always return
>   little-endian byte ordered data. Unfortunately this behavior also means
>   that ioreadX()/iowroteX() and their big-endian counter parts
>   ioreadXbe()/iowriteXbe() are currently broken because they are implemented
>   using the readX()/writeX() functions.
> 
>   Patches 1 and 2 in this series are specific net driver changes that can be
>   applied independently of the final ColdFire readX()/writeX() change.

I read it, it doesn't really answer the question of priority.

> > Is someone still making
> > new SKUs of Coldfire boards? Or (and please don't take this the wrong
> > way) it was a long standing TODO that was tempting to feed to an LLM?  
> 
> It is a long standing todo/fix, but there is nothing LLM anywhere here.
> This was all manually coded and tested. This patch is 95% textual
> substitution, so it wasn't exactly very difficult.
> 
> > IMO keeping the hacks in m68k is a better choice. FEC was used on more
> > modern SoCs, definitely on PPC ones. So we'll be able to get rid of
> > m68k before we can get rid of FEC. Sprinkling m68k workarounds in 
> > the FEC driver is backwards.  
> 
> These changes are not work arounds, they are made to make the FEC driver
> explicitly aware of endianess of the underlying processor and FEC hardware
> block. The code as it is now, that is carrying hacks inside readX and writeX
> for m68k, is trying to hide that from the driver.

Whatever, let me not waste any more time on this. 
If Arnd thinks its worth it:

Acked-by: Jakub Kicinski <kuba@xxxxxxxxxx>