Subject: Re: [PATCH] ARM: dts: ls1021a: output PPS signal on FIPER2

From: Shawn Guo <[email-masked]>
Date: Sun, 17 May 2020 21:54:25 +0800

On Thu, May 14, 2020 at 03:13:45AM +0000, Y.b. Lu wrote:
> Hi Shawn,
> 
> > -----Original Message-----
> > From: Shawn Guo <[email-masked]>
> > Sent: Wednesday, May 13, 2020 4:23 PM
> > To: Y.b. Lu <[email-masked]>
> > Cc: [email-masked]; Leo Li <[email-masked]>;
> > Richard Cochran <[email-masked]>
> > Subject: Re: [PATCH] ARM: dts: ls1021a: output PPS signal on FIPER2
> > 
> > On Mon, Apr 27, 2020 at 11:56:55AM +0800, Yangbo Lu wrote:
> > > Output PPS signal on FIPER2 (Fixed Period Interval Pulse)
> > > which is more desired by user.
> > >
> > > Signed-off-by: Yangbo Lu <[email-masked]>
> > > ---
> > >  arch/arm/boot/dts/ls1021a.dtsi | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/arm/boot/dts/ls1021a.dtsi b/arch/arm/boot/dts/ls1021a.dtsi
> > > index 760a68c..b2ff27a 100644
> > > --- a/arch/arm/boot/dts/ls1021a.dtsi
> > > +++ b/arch/arm/boot/dts/ls1021a.dtsi
> > > @@ -772,7 +772,7 @@
> > >  			fsl,tmr-prsc    = <2>;
> > >  			fsl,tmr-add     = <0xaaaaaaab>;
> > >  			fsl,tmr-fiper1  = <999999995>;
> > > -			fsl,tmr-fiper2  = <99990>;
> > > +			fsl,tmr-fiper2  = <999999995>;
> > 
> > Not sure code change matches patch subject and commit log.  The change
> > is about changing fsl,tmr-fiper2 setting from one value to another.
> 
> The calculation refers to Documentation/devicetree/bindings/ptp/ptp-qoriq.txt. It looks complicated.
> But to be simple, to get 1PPS signal (period is 1s) on FIPER2, the value should be set as,
> fiper2 = <desired period> - <tclk-period> = 1000000000ns - 5ns = 999999995.

Please update commit log to include how new value comes.

Shawn

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