[PATCHv5 05/31] CLK: TI: add support for OMAP gate clock

[Mark Rutland]

On Fri, Aug 02, 2013 at 05:25:24PM +0100, Tero Kristo wrote:
> This node adds support for a clock node which allows control to the
> clockdomain enable / disable.
> 
> Signed-off-by: Tero Kristo <t-kristo at ti.com>
> ---
>  .../devicetree/bindings/clock/ti/gate.txt          |   41 ++++++++
>  arch/arm/mach-omap2/clock.h                        |    9 --
>  drivers/clk/ti/Makefile                            |    2 +-
>  drivers/clk/ti/gate.c                              |  106 ++++++++++++++++++++
>  include/linux/clk/ti.h                             |    8 ++
>  5 files changed, 156 insertions(+), 10 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/clock/ti/gate.txt
>  create mode 100644 drivers/clk/ti/gate.c
> 
> diff --git a/Documentation/devicetree/bindings/clock/ti/gate.txt b/Documentation/devicetree/bindings/clock/ti/gate.txt
> new file mode 100644
> index 0000000..620a73d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/ti/gate.txt
> @@ -0,0 +1,41 @@
> +Binding for Texas Instruments gate clock.
> +
> +This binding uses the common clock binding[1]. This clock is
> +quite much similar to the basic gate-clock [2], however,
> +it supports a number of additional features. If no register
> +is provided for this clock, the code assumes that a clockdomain
> +will be controlled instead and the corresponding hw-ops for
> +that is used.
> +
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> +[2] Documentation/devicetree/bindings/clock/gate-clock.txt
> +
> +Required properties:
> +- compatible : shall be "ti,gate-clock"
> +- #clock-cells : from common clock binding; shall be set to 0
> +- clocks : link to phandle of parent clock
> +
> +Optional properties:
> +- reg : base address for register controlling adjustable gate

Optional? That's odd. If I have a clock with registers, but don't
specify the register, will it still work? i.e. are registerless clocks
really compatible with clocks with registers?.

> +- ti,enable-bit : bit shift for programming the clock gate

Why is this needed? Does the hardware vary wildly, or are several clocks
sharing the same register(s)?

> +- ti,dss-clk : use DSS hardware OPS for the clock
> +- ti,am35xx-clk : use AM35xx hardware OPS for the clock

Those last two sounds like the kind of thing that should be derived from
the compatible string (e.g. ti,am35xx-gate-clock).

> +- ti,clkdm-name : clockdomain to control this gate

As previously mentioned, I'm not a fan of this property. It would make
more sense to describe the domain and have an explicit link to it
(either nodes being children of the domain or having a phandle).

[...]

> +void __init of_omap_gate_clk_setup(struct device_node *node)
> +{
> +       struct clk *clk;
> +       struct clk_init_data init = { 0 };
> +       struct clk_hw_omap *clk_hw;
> +       const char *clk_name = node->name;
> +       int num_parents;
> +       const char **parent_names = NULL;
> +       int i;
> +       u32 val;
> +
> +       clk_hw = kzalloc(sizeof(*clk_hw), GFP_KERNEL);
> +       if (!clk_hw) {
> +               pr_err("%s: could not allocate clk_hw_omap\n", __func__);
> +               return;
> +       }
> +
> +       clk_hw->hw.init = &init;
> +
> +       of_property_read_string(node, "clock-output-names", &clk_name);
> +       of_property_read_string(node, "ti,clkdm-name", &clk_hw->clkdm_name);
> +
> +       init.name = clk_name;
> +       init.flags = 0;
> +
> +       if (of_property_read_u32_index(node, "reg", 0, &val)) {
> +               /* No register, clkdm control only */
> +               init.ops = &omap_gate_clkdm_clk_ops;

If they're truly compatible, you can just see if you can of_iomap, and
if not, continue. Your reg values might be wider than 32 bits, and usig
of_property_read_u32 to read this feels wrong.

> +       } else {
> +               init.ops = &omap_gate_clk_ops;
> +               clk_hw->enable_reg = of_iomap(node, 0);
> +               of_property_read_u32(node, "ti,enable-bit", &val);
> +               clk_hw->enable_bit = val;

What if of_property_read_u32 failed to read the "ti,enable-bit"
property? One might not be present, it's marked as optional in the
binding description.

> +
> +               clk_hw->ops = &clkhwops_wait;
> +
> +               if (of_property_read_bool(node, "ti,dss-clk"))
> +                       clk_hw->ops = &clkhwops_omap3430es2_dss_usbhost_wait;
> +
> +               if (of_property_read_bool(node, "ti,am35xx-clk"))
> +                       clk_hw->ops = &clkhwops_am35xx_ipss_module_wait;

I really don't like this. I think this should be done based on the
compatible string.

Thanks,
Mark.