It was <2017-12-11 pon 15:54>, when Krzysztof Kozlowski wrote: > On Mon, Dec 11, 2017 at 3:06 PM, Łukasz Stelmach <l.stelmach@xxxxxxxxxxx> wrote: >> Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>, Bartlomiej >> Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx> > > This should not appear here. A glitch in a scripted invocation of git-format-patch, fixed. >> Use memcpy_fromio() instead of custom exynos_rng_copy_random() function >> to retrieve generated numbers from the registers of PRNG. >> >> Rearrange the loop around cpu_relax(). In a loop with while() at the >> beginning and the cpu_relax() removed the retry variable is decremented >> twice (down to 98). > > I had troubles with understanding this sentence... and then I figured > out that you are referring to some case without cpu_relax(). I do not > see how it is relevant to this case. Compare the new code with old, > not with some imaginary case without barriers (thus maybe reordered?). > > Your solution is strictly performance oriented so it would be nice to > see here the exact difference in numbers justifying the change. But > only the change for while() -> do-while(), not mixed with > memcpy_fromio. Apparently, after trhough tests, I must admit, the way the status register is being polled is insignificant for the performance. I will remove from the patch any changes in the loop. It is the way, the random bytes are copied from the regiesteres, that makes the difference (5.9 MB/s vs 7.1 MB/s) Thank you very much for your assistance in reaching this conclusion. -- Łukasz Stelmach Samsung R&D Institute Poland Samsung Electronics
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