linux-kernel - Re: AM335x OMAP2 common clock external fixed-clock registration

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Date:	Wed, 15 Apr 2015 15:51:36 -0500
From:	Michael Welling <mwelling@...e.org>
To:	Mike Turquette <mturquette@...aro.org>
Cc:	Tero Kristo <t-kristo@...com>, Stephen Boyd <sboyd@...eaurora.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	devicetree <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Tony Lindgren <tony@...mide.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>
Subject: Re: AM335x OMAP2 common clock external fixed-clock registration

On Wed, Apr 15, 2015 at 01:45:53PM -0700, Mike Turquette wrote:
> On Wed, Apr 15, 2015 at 12:47 PM, Michael Welling <mwelling@...e.org> wrote:
> > On Wed, Apr 15, 2015 at 09:43:30PM +0300, Tero Kristo wrote:
> >> On 04/15/2015 05:09 PM, Michael Welling wrote:
> >> >On Wed, Apr 15, 2015 at 09:34:48AM +0300, Tero Kristo wrote:
> >> >>On 04/15/2015 12:17 AM, Michael Welling wrote:
> >> >>>Greetings,
> >> >>>
> >> >>>I have developed an AM3354 based SoM and it uses an external SI5351 clock
> >> >>>generator to drive the clock inputs for an external duart and I2S audio
> >> >>>master clock. With the registration according to the documentation the
> >> >>>reference clock is not being detected and hence the clock generator is
> >> >>>not working as expect.
> >> >>>
> >> >>>After trying many different things, I started to look around the mailing
> >> >>>lists to find information related to this issue.
> >> >>>
> >> >>>I came acrossed post that has the exact same issue:
> >> >>>https://lkml.org/lkml/2013/2/18/468
> >> >>>
> >> >>>Seeing as the patch did not land upstream, I am wondering if there is
> >> >>>a solution that I am not seeing.
> >> >>>
> >> >>>I am willing to provide a patch given appropriate guidance.
> >> >>
> >> >>Hi Michael,
> >> >>
> >> >>The info on the email you referenced is kind of obsolete, TI SoCs
> >> >>are calling of_clk_init() during boot now, and thus external clock
> >> >>nodes should be registered fine also. Maybe you can provide the
> >> >>actual DTS patch you are trying out so we can help better...? Are
> >> >
> >> >See attached patch and console output.
> >>
> >> I see a bug in your dt data.
> >>
> >> <snip>
> >>
> >> +     clocks {
> >> +             ref27: ref27 {
> >> +                     #clock-cells = <0>;
> >> +                     compatibale = "fixed-clock";
> >>
> >> This should be compatible, right? DT is annoying in that it doesn't
> >> verify property names.
> >>
> >
> > Ooops.
> >
> > Now the clock appears in /sys/kernel/debug/clk:
> > root@...3517-som200:/sys/kernel/debug/clk# cat clk_summary
> >    clock                         enable_cnt  prepare_cnt        rate   accuracy   phase
> > ----------------------------------------------------------------------------------------
> >  ref27                                    0            0    27000000          0 0
> > ...
> >
> > There is still an issue with the si5351.
> >
> > I had to comment out the clk_put here for the frequency to show up:
> > http://lxr.free-electrons.com/source/drivers/clk/clk-si5351.c#L1133
> >
> > Ideas?
> 
> What is the most recent upstream commit that you are based on?

I am working from 4.0.0-rc7.

7b43b47373d40d557cd7e1a84a0bd8ebc4d745ab

> 
> Regards,
> Mike
> 
> >
> >> +                     clock-frequency = <27000000>;
> >> +             };
> >> +     };
> >>
> >> -Tero
> >>
> >> >
> >> >>you seeing any boot time error / warning prints for your new clock?
> >> >
> >> >With the debug messages on you see that the reference clock is not being
> >> >detected.
> >> >
> >> >Whilest debugging I found that the of_clk_get is returning an error no matter
> >> >which clock I pass it:
> >> >http://lxr.free-electrons.com/source/drivers/clk/clk-si5351.c#L1131
> >> >
> >> >>
> >> >>-Tero
> >>
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