linux-kernel - Re: [PATCH] clk: add flags to distinguish xtal clocks

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Date:	Mon, 11 Nov 2013 13:42:47 -0600
From:	Felipe Balbi <balbi@...com>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:	Felipe Balbi <balbi@...com>, <mturquette@...aro.org>,
	<james.hogan@...tec.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	<luca@...lho.fi>,
	Linux ARM Kernel Mailing List 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] clk: add flags to distinguish xtal clocks

Hi,

On Sun, Nov 10, 2013 at 12:37:16PM +0100, Maxime Ripard wrote:
> Hi Felipe,
> 
> On Fri, Nov 08, 2013 at 12:00:48PM -0600, Felipe Balbi wrote:
> > From: Luciano Coelho <luca@...lho.fi>
> > 
> > Add a flag that indicate whether the clock is a crystal or not.
> > 
> > Additionally, parse a new device tree binding in clk-fixed-rate to set
> > this flag.
> > 
> > If clock-xtal isn't set, the clock framework will assume clock to be
> > generated by an oscillator.  There's only one user for this binding
> > right now which is Texas Instruments' WiLink devices which need to know
> > details about the clock in order to initialize the underlying WiFi HW
> > correctly.
> > 
> > Signed-off-by: Luciano Coelho <luca@...lho.fi>
> > Signed-off-by: Felipe Balbi <balbi@...com>
> > ---
> > 
> > Dropped CLK_IS_TYPE_DEFINED flag and just assume that if the flag
> > isn't there, default behavior will be taken.
> > 
> >  Documentation/devicetree/bindings/clock/fixed-clock.txt | 1 +
> >  drivers/clk/clk-fixed-rate.c                            | 6 +++++-
> >  include/linux/clk-provider.h                            | 1 +
> >  3 files changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/clock/fixed-clock.txt b/Documentation/devicetree/bindings/clock/fixed-clock.txt
> > index 0b1fe78..3036dfe 100644
> > --- a/Documentation/devicetree/bindings/clock/fixed-clock.txt
> > +++ b/Documentation/devicetree/bindings/clock/fixed-clock.txt
> > @@ -12,6 +12,7 @@ Required properties:
> >  Optional properties:
> >  - gpios : From common gpio binding; gpio connection to clock enable pin.
> >  - clock-output-names : From common clock binding.
> > +- clock-xtal: true when a clock is provided by a crystal
> >  
> >  Example:
> >  	clock {
> > diff --git a/drivers/clk/clk-fixed-rate.c b/drivers/clk/clk-fixed-rate.c
> > index 1ed591a..5db9bf0 100644
> > --- a/drivers/clk/clk-fixed-rate.c
> > +++ b/drivers/clk/clk-fixed-rate.c
> > @@ -91,13 +91,17 @@ void of_fixed_clk_setup(struct device_node *node)
> >  	struct clk *clk;
> >  	const char *clk_name = node->name;
> >  	u32 rate;
> > +	unsigned long flags = CLK_IS_ROOT;
> >  
> >  	if (of_property_read_u32(node, "clock-frequency", &rate))
> >  		return;
> >  
> > +	if (of_property_read_bool(node, "clock-xtal"))
> > +		flags |= CLK_IS_TYPE_XTAL;
> > +
> 
> Introducing a new compatible instead of a property would make more
> sense here I think.
> 
> Do you have a reason not to do so?

As you can see, this is original work from Luca but I disagree that
adding a new compatible makes more sense. This still related to a fixed
rate clock, we're just giving it one extra metadata which will
differentiate between crystal and oscilator fixed rate clocks.

-- 
balbi

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