Re: [RFC 4/4] m68k: coldfire: fix non-standard readX()/writeX() functions

[Greg Ungerer <gerg@kernel.org>]

Hi Arnd,

On 7/5/26 05:12, Arnd Bergmann wrote:
> On Wed, May 6, 2026, at 16:26, Greg Ungerer wrote:
> 
>> drivers/dma/mcf-edma-main.c
>>    Supports big-endian access by setting the big-endian flag of
>>    the drivers struct fsl_edma_engine. But locally should be using
>>    ioread32be() and iowrite32be() instead of ioread32() and iowrite32().
> 
> I'm still a bit confused about how this works at the moment,
> since the drivers/dma/fsl-edma-common.h file already contains
> checks for the edma->big_endian flag, which is set in
> mcf_edma_probe(). The version after your patch makes sense
> to me, but it looks like the existing code cannot work.

Yes, it certainly doesn't look right to me either.

Angelo: you look to be the original author of this driver, can you shed any
light on its working status in mainline currently?


>> drivers/spi/spi-fsl-dspi.c
>>    Setting the regmap format_endian flags to use native endian will
>>    force driver to use appropriate big or little endian access on
>>    whatever platform it is built for.
>>
>> These drivers have only been compile tested.
> 
> I would suggest marking these as explicit BIG_ENDIAN rather than
> NATIVE_ENDIAN. The effect should be the same since coldfire CPUs
> cannot run little-endian code, but the way that hardware usually
> works is that the endianess is fixed at the bus level to one way
> or the other. NATIVE_ENDIAN to me implies that the registers
> have configurable endianess that is switched along with the CPU
> mode.

Ok, will change. I chose native endian in this case since the regmap config
entry used for the m5441x family is also used by the vf610 devce (which looks
to be an ARM imx SoC). So it will need a duplicate setup with those endian
flags set to BIG_ENDIAN. But that is no problem.

Thanks
Greg