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    SubjectRe: [PATCH] drm/i915: use udelay for very short delays
    On Thu, Dec 15, 2016 at 11:08:49AM +0200, Jani Nikula wrote:
    > On Thu, 15 Dec 2016, Nicholas Mc Guire <hofrat@osadl.org> wrote:
    > > Even on fast systems a 2 microsecond delay is most likely more efficient
    > > as a busy-wait loop. The overhead of a hrtimer does not seem warranted -
    > > change this to a udelay(2).
    >
    > Similar concerns as in [1]. We don't need the accuracy of udelay() here,
    > so this boils down to which is the better use of CPU. We could probably
    > relax the max delay more if that was helpful. But I'm not immediately
    > sold on "is most likely more efficient" which sounds like a gut feeling.
    >
    > I'm sorry it's not clear in my other reply that I do appreciate
    > addressing incorrect/silly use of usleep_range(); I'm just not (yet)
    > convinced udelay() is the answer.

    if the delay is not critical and all that is needed
    is an assurance that it is greater than X us then
    usleep_range is fine with a relaxed limit.
    So from what you wrote my patch proposal is wrong - the
    udelay() is not the way to got.
    My intent is to get rid of very small usleep_range() cases
    so if usleep_range(20,50) causes no issues with this driver
    and does not induce any performance penalty then that would
    be the way to go I think.

    thx!
    hofrat

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