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LKML: Robert Walsh: Re: [PATCH 07/13] [RFC] ipath core misc files
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McKenney"</a></li></ul></li><li><a href="/lkml/2005/12/17/75">Andrew Morton</a><ul><li><a href="/lkml/2005/12/20/295">Robert Walsh</a></li></ul></li></ul></li></ul></li><li><a href="/lkml/2005/12/17/74">Andrew Morton</a><ul><li class="origin"><a href="">Robert Walsh</a></li><li><a href="/lkml/2005/12/17/90">Robert Walsh</a><ul><li><a href="/lkml/2005/12/17/124">Andrew Morton</a><ul><li><a href="/lkml/2005/12/17/125">Robert Walsh</a></li></ul></li></ul></li></ul></li></ul></li></ul></td><td width="32" rowspan="2" class="c" valign="top"><img src="/images/icornerl.gif" width="32" height="32" alt="/" /></td><td class="c" rowspan="2" valign="top" style="padding-top: 1em"><table><tr><td><table><tr><td class="lp">Subject</td><td class="rp" itemprop="name">Re: [PATCH 07/13] [RFC] ipath core misc files</td></tr><tr><td class="lp">From</td><td class="rp" itemprop="author">Robert Walsh <></td></tr><tr><td class="lp">Date</td><td class="rp" itemprop="datePublished">Sat, 17 Dec 2005 13:29:23 -0800</td></tr></table></td><td></td></tr></table><pre itemprop="articleBody">> > +void ipath_init_picotime(void)<br />> > +{<br />> > + int i;<br />> > + u_int64_t ts, te, delta = -1ULL;<br />> > +<br />> > + for (i = 0; i < 5; i++) {<br />> > + ts = get_cycles();<br />> > + udelay(250);<br />> > + te = get_cycles();<br />> > + if ((te - ts) < delta)<br />> > + delta = te - ts;<br />> > + yield();<br />> > + }<br />> > + _ipath_pico_per_cycle = 250000000 / delta;<br />> > +}<br />> <br />> hm, I hope this is debug code which is going away. If not, we should take<br />> a look at what it's trying to do here.<br /><br />This isn't debug code. It's used to calculate the roughly number<br />picoseconds per cycle. This is used in the driver to make sure<br />HyperTransport reads haven't timed out (see ipath_snap_cntr in<br />ipath_driver.c) when reading chip counters. If you can think of a<br />better way of figuring out whether a read took greater than a certain<br />length of time, I'd be interested in knowing it.<br /><br />Regards,<br /> Robert.<br /><br />-- <br />Robert Walsh Email: rjwalsh@pathscale.com<br />PathScale, Inc. 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