From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Cochran Subject: Re: [PATCH 7/9] net: ethernet: ti: cpts: calc mult and shift from refclk freq Date: Wed, 14 Sep 2016 16:22:11 +0200 Message-ID: <20160914142210.GE28592@localhost.localdomain> References: <20160914130231.3035-1-grygorii.strashko@ti.com> <20160914130231.3035-8-grygorii.strashko@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , netdev@vger.kernel.org, Mugunthan V N , Sekhar Nori , linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, WingMan Kwok To: Grygorii Strashko Return-path: Received: from mail-wm0-f68.google.com ([74.125.82.68]:34193 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932773AbcINOWR (ORCPT ); Wed, 14 Sep 2016 10:22:17 -0400 Content-Disposition: inline In-Reply-To: <20160914130231.3035-8-grygorii.strashko@ti.com> Sender: netdev-owner@vger.kernel.org List-ID: 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. > 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. > + 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, Richard