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

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Message-ID: <5f83750ca7c146f7080444b85dc58f51cc0b3b35.camel@buserror.net>
Date:   Fri, 21 Dec 2018 22:35:45 -0600
From:   Scott Wood <oss@...error.net>
To:     Andy Tang <andy.tang@....com>
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

On Wed, 2018-12-12 at 01:57 +0000, Andy Tang wrote:
> > -----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.

OK.

> 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

That will be the branch I use to send the patches to Michael, but it's not a
branch that is kept constantly updated.  If you're asking what tree to base
future patches on, that would generally be the next branch of
powerpc/linux.git (unless you depend on something else that isn't there yet).

-Scott