On Thu, Sep 26, 2013 at 03:34:33PM -0700, Jesse Barnes wrote:
> On Thu, 26 Sep 2013 23:25:46 +0100
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > >
> > > if (!intel_enable_rc6(dev))
> > > return 0;
> > >
> > > - raw_time = I915_READ(reg) * 128ULL;
> > > - return DIV_ROUND_UP_ULL(raw_time, 100000);
> > > + /* On VLV, residency time is in CZ units rather than 1.28us */
> > > + if (IS_VALLEYVIEW(dev)) {
> > > + u32 clkctl2;
> > > +
> > > + clkctl2 = I915_READ(VLV_CLK_CTL2) >>
> > > + CLK_CTL2_CZCOUNT_30NS_SHIFT;
> > > + if (!clkctl2) {
> > > + WARN(!clkctl2, "bogus CZ count value");
> > > + return 0;
> > > + }
> > > + units = DIV_ROUND_UP_ULL(3000ULL, (u64)clkctl2);
> >
> > For your divisor, this should 30*1000 not 3*1000.
>
> 30ns * 100 for fixed point precision, just as above.
>
> >
> > > + if (I915_READ(VLV_COUNTER_CONTROL) & VLV_COUNT_RANGE_HIGH)
> > > + units <<= 8;
> > > +
> > > + div = 100 000 000;
>
> Then here we divide out the ns to ms (1000000) and also the 100 for
> fixed point.
>
> Or do I still have it wrong?
Just counting fail on my part, even after splitting it up to make it
easier for myself.
How about
#define BIAS 100
units = 30*BIAS / cltctk2;
if (hi) units <<= 8;
div = NSEC_PER_MSEC * BIAS;
All because I have difficultly counting.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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