Re: [PATCH 7/9] net: ethernet: ti: cpts: calc mult and shift from refclk freq

[Grygorii Strashko]

On 09/14/2016 05:22 PM, Richard Cochran wrote:
> On Wed, Sep 14, 2016 at 04:02:29PM +0300, Grygorii Strashko wrote:
> > @@ -35,6 +33,8 @@ Optional properties:
> >  			  For example in dra72x-evm, pcf gpio has to be
> >  			  driven low so that cpsw slave 0 and phy data
> >  			  lines are connected via mux.
> > +- cpts_clock_mult	: Numerator to convert input clock ticks into nanoseconds
> > +- cpts_clock_shift	: Denominator to convert input clock ticks into nanoseconds
>
> You should explain to the reader how these will be calculated when the
> properties are missing.

Not sure how full should it be explained in bindings - I'll try.


> > diff --git a/drivers/net/ethernet/ti/cpts.c b/drivers/net/ethernet/ti/cpts.c
> > index ff8bb85..8046a21 100644
> > --- a/drivers/net/ethernet/ti/cpts.c
> > +++ b/drivers/net/ethernet/ti/cpts.c
> > @@ -418,18 +418,60 @@ void cpts_unregister(struct cpts *cpts)
> >  	clk_disable(cpts->refclk);
> >  }
> >
> > +static void cpts_calc_mult_shift(struct cpts *cpts)
> > +{
> > +	u64 maxsec;
> > +	u32 freq;
> > +	u32 mult;
> > +	u32 shift;
> > +	u64 ns;
> > +	u64 frac;
>
> Why so many new lines?  This isn't good style.  Please combine
> variables of the same type into one line and sort the lists
> alphabetically.

Its matter of preferences :), but sure - I'll update.
> > +	if (cpts->cc_mult || cpts->cc.shift)
> > +		return;
> > +
> > +	freq = clk_get_rate(cpts->refclk);
> > +
> > +	/* Calc the maximum number of seconds which we can run before
> > +	 * wrapping around.
> > +	 */
> > +	maxsec = cpts->cc.mask;
> > +	do_div(maxsec, freq);
> > +	if (!maxsec)
> > +		maxsec = 1;
> > +	else if (maxsec > 600 && cpts->cc.mask > UINT_MAX)
> > +		maxsec = 600;
> > +
> > +	clocks_calc_mult_shift(&mult, &shift, freq, NSEC_PER_SEC, maxsec);
> > +
> > +	cpts->cc_mult = mult;
> > +	cpts->cc.mult = mult;
> > +	cpts->cc.shift = shift;
> > +	/* Check calculations and inform if not precise */
>
> Contrary to this comment, you are not making any kind of judgment
> about whether the calculations are precise or not.
>
> > +	frac = 0;
> > +	ns = cyclecounter_cyc2ns(&cpts->cc, freq, cpts->cc.mask, &frac);
> > +
> > +	dev_info(cpts->dev,
> > +		 "CPTS: ref_clk_freq:%u calc_mult:%u calc_shift:%u error:%lld nsec/sec\n",
> > +		 freq, cpts->cc_mult, cpts->cc.shift, (ns - NSEC_PER_SEC));
> > +}
> > +

Thanks for the review.

--
regards,
-grygorii