Re: [PATCH] clk: Add device tree binding to clk-fixed-factor

Christian Ruppert
2013-04-11T09:20:34Z

Hi Gregory,

Since there doesn't seem to be anyone opposing this feature I just
checked your patch and after adding the CLK_OF_DECLARE macro in the end
it works well for us. Tell me if you would like to rebase and resubmit
your patch or if I should follow up on our own.

Greetings,
Christian

On Wed, Apr 10, 2013 at 06:27:47PM +0200, christian ruppert wrote:
> Hi Gregory,
>
> We use derived clocks with fixed ratios for our TB10x platform. I
> originally had this in the platform code but Vineet (the platform
> maintainer) rightly pointed out that the common clock framework would
> be the correct place for it.
> Is there any reason not to support this functionality? After all, the
> generic fixed rate clock also has a device tree binding and I'd guess
> we're not the only ones statically deriving one clock from another in
> our SOCs.
>
> Greetings,
> Christian
>
> On Wed, Apr 10, 2013 at 05:56:25PM +0200, Gregory CLEMENT wrote:
> > Hi Christian,
> >
> > On 04/10/2013 05:40 PM, Christian Ruppert wrote:
> > > This patch adds a device tree binding for the simple fixed factor clock
> > > divider/multiplier of the common clock tree binding.
> >
> > This patch remind me of something :
> > http://lists.infradead.org/pipermail/linux-arm-kernel/2012-August/116405.html
> >
> > Do you have a use case for it, this time?
> >
> > My version have been hold off waiting for an user for it.
> > Will you need it for a driver?
> >
> > Regards,
> >
> > >
> > > Signed-off-by: Christian Ruppert <christian.ruppert@abilis.com>
> > > ---
> > > .../bindings/clock/fixed-factor-clkdiv.txt | 24 +++++++++++++++
> > > drivers/clk/clk-fixed-factor.c | 32 ++++++++++++++++++++
> > > include/linux/clk-provider.h | 1 +
> > > 3 files changed, 57 insertions(+), 0 deletions(-)
> > > create mode 100644 Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt
> > >
> > > diff --git a/Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt b/Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt
> > > new file mode 100644
> > > index 0000000..352bac4
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/clock/fixed-factor-clkdiv.txt
> > > @@ -0,0 +1,24 @@
> > > +Device Tree Clock bindings for plat-tb10x
> > > +
> > > +This binding uses the common clock binding[1].
> > > +
> > > +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> > > +
> > > +Required properties:
> > > +- compatible : shall be "fixed-factor-clkdiv"
> > > +- #clock-cells: from common clock binding; shall be set to 0
> > > +- clocks: shall be the input parent clock phandle for the clock.
> > > +- clock-mult: defines the multiplication factor of the output clock frequency
> > > + wrt. the input clock frequency.
> > > +- clock-div: defines the division factor of the output clock frequency wrt.
> > > + the input clock frequency.
> > > +
> > > +Example:
> > > +cpu_clk: clkdiv_cpu { /* CPU clock derived from pll0. 1/2 of pll frequency */
> > > + compatible = "fixed-factor-clkdiv";
> > > + #clock-cells = <0>;
> > > + clocks = <&pll0>;
> > > + clock-mult = <1>;
> > > + clock-div = <2>;
> > > + clock-output-names = "cpu_clk";
> > > +};
> > > diff --git a/drivers/clk/clk-fixed-factor.c b/drivers/clk/clk-fixed-factor.c
> > > index 1ef271e..85e45f1 100644
> > > --- a/drivers/clk/clk-fixed-factor.c
> > > +++ b/drivers/clk/clk-fixed-factor.c
> > > @@ -11,6 +11,7 @@
> > > #include <linux/clk-provider.h>
> > > #include <linux/slab.h>
> > > #include <linux/err.h>
> > > +#include <linux/of.h>
> > >
> > > /*
> > > * DOC: basic fixed multiplier and divider clock that cannot gate
> > > @@ -96,3 +97,34 @@ struct clk *clk_register_fixed_factor(struct device *dev, const char *name,
> > >
> > > return clk;
> > > }
> > > +
> > > +#ifdef CONFIG_OF
> > > +/**
> > > + * of_fixed_factor_clkdiv_setup() - Set up simple fixed factor clock divider
> > > + */
> > > +void of_fixed_factor_clkdiv_setup(struct device_node *node)
> > > +{
> > > + struct clk *clk;
> > > + const char *clk_name = node->name;
> > > + const char *parent_name;
> > > + u32 mult, div;
> > > +
> > > + if (of_property_read_u32(node, "clock-mult", &mult))
> > > + return;
> > > +
> > > + if (of_property_read_u32(node, "clock-div", &div))
> > > + return;
> > > +
> > > + parent_name = of_clk_get_parent_name(node, 0);
> > > +
> > > + of_property_read_string(node, "clock-output-names", &clk_name);
> > > +
> > > + clk = clk_register_fixed_factor(NULL, clk_name, parent_name, 0,
> > > + mult, div);
> > > + if (!IS_ERR(clk))
> > > + of_clk_add_provider(node, of_clk_src_simple_get, clk);
> > > +}
> > > +EXPORT_SYMBOL_GPL(of_fixed_factor_clkdiv_setup);
> > > +CLK_OF_DECLARE(fixed_clkdiv, "fixed-factor-clkdiv",
> > > + of_fixed_factor_clkdiv_setup);
> > > +#endif
> > > diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> > > index 7f197d7..d4937cf 100644
> > > --- a/include/linux/clk-provider.h
> > > +++ b/include/linux/clk-provider.h
> > > @@ -184,6 +184,7 @@ struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
> > > unsigned long fixed_rate);
> > >
> > > void of_fixed_clk_setup(struct device_node *np);
> > > +void of_fixed_factor_clkdiv_setup(struct device_node *node);
> > >
> > > /**
> > > * struct clk_gate - gating clock
> > >
> >
> >
> > --
> > Gregory Clement, Free Electrons
> > Kernel, drivers, real-time and embedded Linux
> > development, consulting, training and support.
> > http://free-electrons.com
>
> --
> Christian Ruppert , <christian.ruppert@abilis.com>
> /|
> Tel: +41/(0)22 816 19-42 //| 3, Chemin du Pré-Fleuri
> _// | bilis Systems CH-1228 Plan-les-Ouates

--
Christian Ruppert , <christian.ruppert@abilis.com>
/|
Tel: +41/(0)22 816 19-42 //| 3, Chemin du Pré-Fleuri
_// | bilis Systems CH-1228 Plan-les-Ouates