linux-kernel - Re: [PATCH v2] powerpc/dts: Add and fix 1588 timer node for eTSEC

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Message-ID: <1437750459.2993.224.camel@freescale.com>
Date:	Fri, 24 Jul 2015 10:07:39 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Lu Yangbo-B47093 <yangbo.lu@...escale.com>
CC:	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] powerpc/dts: Add and fix 1588 timer node for eTSEC

On Mon, 2015-07-20 at 01:33 -0500, Lu Yangbo-B47093 wrote:
> > On Wed, 2015-07-15 at 21:37 -0500, Lu Yangbo-B47093 wrote:
> > > Any comments?
> > > Thanks.
> > 
> > Sorry, I must have missed this on my last time through the patch queue.
> > I see you've decimalized the fiper and max-adj properties, which is
> > good... but does it really make sense for tmr-add?  I'm not familiar with
> > what this value represents, but the numbers look more natural as hex (e.g.
> > 0xaaaaaaab versus 2863311531).
> 
> Yes, the fiper value would be writed into fiper registers. And max-adj 
> value would be used in ptp driver in driver/ptp/.
> But you insisted that values should be in decimalism in the v1 patch... :)
> 
> See the history :)

I didn't insist on decimals for *everything*, just where it makes sense, and 
that "it goes in a register" doesn't *automatically* mean that it doesn't 
make sense.

################# history ##################
> > > +  ptp_clock@...00{
> > > +         compatible = "fsl,etsec-ptp";
> > > +         reg = <0xb0e00 0xb0>;
> > > +         interrupts = <68 2 0 0 69 2 0 0>;
> > > +         fsl,tclk-period = <5>;
> > > +         fsl,tmr-prsc    = <2>;
> > > +         fsl,tmr-add     = <0xcccccccd>;
> > > +         fsl,tmr-fiper1  = <0x3b9ac9fb>;
> > > +         fsl,tmr-fiper2  = <0x00018696>;
> > > +         fsl,max-adj     = <249999999>;
> > 
> > Please don't use hex for numbers that make more sense as decimal.
> > [Lu Yangbo-B47093] The hex value is register value, I think it's better 
> > to use hex.
> 
> Whether it goes into a register doesn't matter.  Hex values are useful for 
> values which are subdivided into various bitfields, or whose hex 
> representation is simpler than decimal.  I'm not familiar with the details 
> of this hardware, but I doubt the former is the case for 0x3b9ac9fb == 
> 9999999995 or 0x18696 == 99990.
> 
> -Scott
> ######################################
> 
> 
> > 
> > > > diff --git a/arch/powerpc/boot/dts/p2020rdb-pc.dtsi
> > > > b/arch/powerpc/boot/dts/p2020rdb-pc.dtsi
> > > > index c21d1c7..363172d 100644
> > > > --- a/arch/powerpc/boot/dts/p2020rdb-pc.dtsi
> > > > +++ b/arch/powerpc/boot/dts/p2020rdb-pc.dtsi
> > > > @@ -215,12 +215,12 @@
> > > >     };
> > > > 
> > > >      ptp_clock@...00{
> > > > -           fsl,tclk-period = <5>;
> > > > -           fsl,tmr-prsc = <200>;
> > > > -           fsl,tmr-add = <0xCCCCCCCD>;
> > > > -           fsl,tmr-fiper1 = <0x3B9AC9FB>;
> > > > -           fsl,tmr-fiper2 = <0x0001869B>;
> > > > -           fsl,max-adj = <249999999>;
> > > > +           fsl,tclk-period = <5>;
> > > > +           fsl,tmr-prsc    = <2>;
> > > > +           fsl,tmr-add     = <2863311531>;
> > > > +           fsl,tmr-fiper1  = <999999995>;
> > > > +           fsl,tmr-fiper2  = <99990>;
> > > > +           fsl,max-adj     = <299999999>;
> > > >     };
> > 
> > And here, you're changing the value of fsl,tmr-add and fsl,max-adj.  Why?
> 
> The old values maybe not calculated base on the default eTSEC system clock 
> value.
> 1588 timer couldn’t be adjusted correctly by old values.

Explain in the changelog what was wrong with the old values (don't just say 
"Fix 1588 timer node in file").

-Scott

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