[alsa-devel] [PATCH 4/4] ASoC: fsl: make fsl_ssi driver compilable on ARM/IMX

[Russell King - ARM Linux]

On Fri, Feb 24, 2012 at 03:29:04PM -0600, Timur Tabi wrote:
> Russell King - ARM Linux wrote:
> >> > I'll have to ask around, because I'm sure I'm missing something.
> > If what you say is true, it means we have different semantics for the
> > same accessors on different architectures.  No wonder it's needing
> > drivers to gain ifdefs to select appropriate accessors.
> > 
> > This needs sorting out properly.  It needs the semantics of readl() etc
> > to be fully defined, and all architectures to implement those semantics
> > rather than what they think would be appropriate for them.
> 
> So I asked around, and sure enough, my macro-fu was weak.  On PowerPC,
> readl() maps to in_le32().  Even though PowerPC is big-endian, some
> devices are little endian (e.g. PCI and some PICs).
> 
> in_le32() is the byte-swapping version of in_be32().  Both functions have
> instruction order synchronization instructions in them.
> 
> So replacing in_be32() with readl() will break on PowerPC.

But not a BE variant.  Like ioread32be().

BenH tells me that he'll accept patches which converts in_32be() to
ioread32be(), as in_32be() is ancient PPC cruft that needs to die.