[Intel-wired-lan] [PATCH v7 0/7] netdev: intel: Eliminate duplicate barriers on weakly-ordered archs

[Lino Sanfilippo]

Hi,

> Double sorry now.
> 
> I don't know if you have been following "RFC on writel and writel_relaxed" thread
> or not but there are some new developments about wmb() requirement. 

Just out of interest: Where can this thread be found?

> 
> Basically, wmb() should never be used before writel() as writel() seem to
> provide coherency and observability guarantee.
> 

AFAIU memory-barriers.txt writel() only guarantees correct order of accesses to
IO-memory not RAM vs. IO-memory (this may be the case for some architectures 
where the writel() implementation contains a wmb() but not for all).
For the RAM vs. IO-memory case at least a a wmb()/rmb() has to be used. 
Is this not correct? 

Regards,
Lino