linux-kernel - RE: [PATCH 1/2 v3] powerpc/fsl: Use new clockgen binding

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Date:   Wed, 12 Dec 2018 01:57:10 +0000
From:   Andy Tang <andy.tang@....com>
To:     Scott Wood <oss@...error.net>
CC:     "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        "paulus@...ba.org" <paulus@...ba.org>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: RE: [PATCH 1/2 v3] powerpc/fsl: Use new clockgen binding



> -----Original Message-----
> From: Scott Wood <oss@...error.net>
> Sent: 2018年11月26日 9:19
> To: Andy Tang <andy.tang@....com>
> Cc: mturquette@...libre.com; sboyd@...nel.org; robh+dt@...nel.org;
> mark.rutland@....com; benh@...nel.crashing.org; paulus@...ba.org;
> mpe@...erman.id.au; linux-clk@...r.kernel.org;
> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org;
> linuxppc-dev@...ts.ozlabs.org
> Subject: Re: [PATCH 1/2 v3] powerpc/fsl: Use new clockgen binding
> 
> On Wed, 2018-10-31 at 14:57 +0800, Yuantian Tang wrote:
> > From: Scott Wood <oss@...error.net>
> >
> > The driver retains compatibility with old device trees, but we don't
> > want the old nodes lying around to be copied, or used as a reference
> > (some of the mux options are incorrect), or even just being clutter.
> >
> >
> > +sysclk: sysclk {
> > +	compatible = "fixed-clock";
> > +	#clock-cells = <0>;
> > +	clock-frequency = <100000000>;
> > +	clock-output-names = "sysclk";
> > +};
> > +
> >  clockgen: global-utilities@...00 {
> 
> The U-Boot fixup won't work with this.  U-Boot patches the frequency
> directly into the clockgen node (BTW, this is another reason to preserve
> the generic
> 1.0/2.0 compatible string).  The new binding does not require an input
> clock node when it is provided as clock-frequency directly in the clockgen
> node -- and the sysclk node was not in my original patch (nor did you note
> that you made changes from that original).  Why did you add it?
> 
> I would just remove it when applying, but I'm concerned that this indicates
> a lack of testing (and I don't have the hardware access to test it myself,
> except on t4240) -- unless the 100 MHz sysclk just happened to be correct
> on the machines you tested (which would also be a test coverage
> problem)?
[Andy] You are right. Sysclk may not be useful anymore. 
Uboot will fixup the clockgen node correctly. Please apply this patch without sysclk. We will
test it and catch the error if the clock is not fixed correctly.

BTW, which git tree are you going to apply it on? This one?
https://git.kernel.org/pub/scm/linux/kernel/git/scottwood/linux.git/log/?h=next

BR,
Andy
> 
> -Scott
>