linux-kernel - Re: [PATCH] ASoC: rt5651: use msleep for large delays

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Message-ID: <20170111150645.GB16045@osadl.at>
Date:   Wed, 11 Jan 2017 15:06:45 +0000
From:   Nicholas Mc Guire <der.herr@...r.at>
To:     Mark Brown <broonie@...nel.org>
Cc:     Nicholas Mc Guire <hofrat@...dl.org>,
        Bard Liao <bardliao@...ltek.com>,
        Oder Chiou <oder_chiou@...ltek.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: rt5651: use msleep for large delays

On Wed, Jan 11, 2017 at 02:59:26PM +0000, Mark Brown wrote:
> On Wed, Jan 11, 2017 at 12:49:36PM +0100, Nicholas Mc Guire wrote:
> 
> >  		if (!rt5651->hp_mute)
> > -			usleep_range(80000, 85000);
> > +			msleep(85);
> 
> If you're doing conversions like this I'd expect us to be picking the
> lower number rather than the higher number - people are saying "wait for
> at least X and at most Y" and msleep() is "wait for at least X" so we
> should be picking X.

useleep_range() sets the timer to max and only if there happens to be a
timer between min and max uses that - so the mean of runs is generally
a bit above max. E.g.

usleep_range(*,200) 5000 samples - idle system
 100,200         190,200
 Min.   :188481  Min.   :197793
 1st Qu.:207062  1st Qu.:207051
 Median :207139  Median :207133
 Mean   :207254  Mean   :207244
 3rd Qu.:207341  3rd Qu.:207610
 Max.   :225340  Max.   :214885

So to keep the behavior as close to the current code as possible
it seemed better to select the upper value.

Am I missing something ?

thx!
hofrat