On Tue, 2018-03-27 at 08:42 -0400, Sinan Kaya wrote: > On 3/23/2018 10:34 PM, okaya@xxxxxxxxxxxxxx wrote: > > On 2018-03-23 19:58, Jeff Kirsher wrote: > > > On Fri, 2018-03-23 at 14:53 -0700, Alexander Duyck wrote: > > > > On Fri, Mar 23, 2018 at 11:52 AM, Sinan Kaya <okaya@codeaurora. > > > > org> > > > > wrote: > > > > > Code includes wmb() followed by writel() in multiple places. > > > > > writel() > > > > > already has a barrier on some architectures like arm64. > > > > > > > > > > This ends up CPU observing two barriers back to back before > > > > > executing > > > > > the > > > > > register write. > > > > > > > > > > Since code already has an explicit barrier call, changing > > > > > writel() to > > > > > writel_relaxed(). > > > > > > > > > > I did a regex search for wmb() followed by writel() in each > > > > > drivers > > > > > directory. > > > > > I scrubbed the ones I care about in this series. > > > > > > > > > > I considered "ease of change", "popular usage" and > > > > > "performance > > > > > critical > > > > > path" as the determining criteria for my filtering. > > > > > > > > > > We used relaxed API heavily on ARM for a long time but > > > > > it did not exist on other architectures. For this reason, > > > > > relaxed > > > > > architectures have been paying double penalty in order to use > > > > > the > > > > > common > > > > > drivers. > > > > > > > > > > Now that relaxed API is present on all architectures, we can > > > > > go and > > > > > scrub > > > > > all drivers to see what needs to change and what can remain. > > > > > > > > > > We start with mostly used ones and hope to increase the > > > > > coverage over > > > > > time. > > > > > It will take a while to cover all drivers. > > > > > > > > > > Feel free to apply patches individually. > > > > > > > > I looked over the set and they seem good. > > > > > > > > Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx> > > > > > > Grrr, patch 1 does not apply cleanly to my next-queue tree (dev- > > > queue > > > branch). I will deal with this series in a day or two, after I > > > have dealt > > > with my driver pull requests. > > > > Sorry, you will have to replace the ones you took from me. > > 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. > > Basically, wmb() should never be used before writel() as writel() > seem to > provide coherency and observability guarantee. > > wmb()+writel_relaxed() is slower on some architectures than plain > writel() > > I'll have to rework these patches to have writel() only. > > Are you able to drop the applied ones so that I can post V8 or is it > too late? Currently I do not have any of your patches applied to my next-queue tree (dev-queue branch). So feel free to do any revisions you need to do and to re-submit to intel-wired-lan@xxxxxxxxxxxxxxxx (IWL) mailing list.
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