> > On 3/27/2018 10:04 AM, Lino Sanfilippo wrote: > > 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? > > https://www.spinics.net/lists/linux-rdma/msg62570.html > > https://patchwork.kernel.org/patch/10309913/ > > > > > >> > >> 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? > > We are being told that if you use writel(), then you don't need a wmb() on > all architectures. > > Jason is seeking behavior clarification for write combined buffers. > Interesting, thanks for the information! Lino -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
