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. > > Regards, > Lino > -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project. -- 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
