Re: [RESEND PATCH 1/1] clk: add DT support for clock gating control

[Rob Herring]

On 07/12/2012 02:15 AM, Sebastian Hesselbarth wrote:
> As Rob's clock binding support patch is now up on clk-next, I'd like to
> draw attention on this patch again.
> -- 
> This patch adds support for using clock gates (clk-gate) from DT based
> on Rob Herrings DT clk binding support for 3.6.
> 
> It adds a helper function to clk-gate to allocate all resources required by
> a set of individual clock gates, i.e. register base address and lock. Each
> clock gate is described as a child of the clock-gating-control in DT and
> also created by the helper function.
> 
> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@xxxxxxxxxxxxxx>
> Cc: Grant Likely <grant.likely@xxxxxxxxxxxx>
> Cc: Rob Herring <rob.herring@xxxxxxxxxxx>
> Cc: Rob Landley <rob@xxxxxxxxxxx>
> Cc: Mike Turquette <mturquette@xxxxxx>
> Cc: devicetree-discuss@xxxxxxxxxxxxxxxx
> Cc: linux-doc@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> ---
>  .../bindings/clock/clock-gating-control.txt        |   80
> +++++++++++++++++++
>  drivers/clk/clk-gate.c                             |   84
> ++++++++++++++++++++
>  include/linux/clk-provider.h                       |    2 +
>  3 files changed, 166 insertions(+)
>  create mode 100644
> Documentation/devicetree/bindings/clock/clock-gating-control.txt
> 
> diff --git
> a/Documentation/devicetree/bindings/clock/clock-gating-control.txt
> b/Documentation/devicetree/bindings/clock/clock-gating-control.txt
> new file mode 100644
> index 0000000..05f5728
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/clock-gating-control.txt
> @@ -0,0 +1,80 @@
> +Binding for simple clock gating control based on clock gate register
> with one
> +bit per clock gate. This is a clock consumer and also a clock provider
> for a
> +set of gated clocks that are described as children of this node. Each
> clock gate
> +is described by a bit number and polarity to control the gate.
> +
> +This binding uses the common clock binding[1].
> +
> +[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
> +
> +==Clock gating control==
> +
> +Required properties:
> +- compatible : shall be "clock-gating-control".
> +- reg : should contain the register physical address and length for
> +        the clock gating control.
> +- clocks : shared parent clock for all gated clocks.
> +- #clock-cells : from common clock binding; shall be set to 0.
> +- #address-cells : number of cells required to describe a clock gate;
> +                   should be <2>.
> +- #size-cells : should be zero.
> +
> +Each individual clock gate bit is described as a child of the
> +corresponding gating control register with the following properties.
> +
> +Required child properties:
> +- reg : should contain the individual bit and polarity to control
> +        the clock gate. A polarity of 0 means that by setting the
> +        bit to 1 the clock passes through the clock gate while
> +    setting the bit to 0 disables the clock. Any other value
> +         for polarity inverts the meaning of the control bit.

This is a bit of overloading reg to specify the polarity.

> +
> +Optional child properties:
> +- clocks : overrides the shared parent clock for this clock gate
> +           by the clock passed in this property.
> +- clock-output-names : from common clock binding; allows to set
> +                       a specific name for the gated clock output.
> +
> +==Example==
> +
> +    /* fixed root clock */
> +    osc: oscillator {
> +        compatible = "fixed-clock";
> +        #clock-cells = <0>;
> +        clock-frequency = <166666667>;
> +    };
> +
> +    /* sata peripheral clock */
> +    sata_clk: ext-oscillator {
> +        compatible = "fixed-clock";
> +        #clock-cells = <0>;
> +        clock-frequency = <25000000>;
> +    };
> +
> +    /* register-based clock gating control */
> +    gating-control@f10d0038 {
> +        compatible = "clock-gating-control";
> +        reg = <0xf10d0038 0x4>;
> +        clocks = <&osc>;
> +        #clock-cells = <0>;
> +        #address-cells = <2>;
> +        #size-cells = <0>;
> +
> +        /* USB0 clock gate on register bit 0 with inverted polarity */
> +        cg_usb0: clockgate@0 {
> +            reg = <0 1>; /* register bit 0, inverted polarity */
> +        };
> +
> +        /* PCIe0 clock gate on register bit 1 with normal polarity
> +         * and named output clock */
> +        cg_pcie0: clockgate@1 {
> +            reg = <1 0>; /* register bit 1, normal polarity */
> +            clock-output-names = "pcie0_clk";
> +        };
> +
> +        /* SATA clock gate with different parent clock */
> +        cg_sata: clockgate@3 {
> +            reg = <3 0>; /* register bit 3, normal polarity */
> +            clocks = <&sata_clk>;
> +        };

I'm not sure I like the node per bit. What about a bit mask for valid
bits and polarities. Then add a clock cell to specify the bit or index.

i.MX has 2-bit enable fields for its leaf clocks, so how and if you
would support that is something to think about.

Rob

> +    };
> diff --git a/drivers/clk/clk-gate.c b/drivers/clk/clk-gate.c
> index 578465e..1e88907 100644
> --- a/drivers/clk/clk-gate.c
> +++ b/drivers/clk/clk-gate.c
> @@ -15,6 +15,9 @@
>  #include <linux/io.h>
>  #include <linux/err.h>
>  #include <linux/string.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
>   /**
>   * DOC: basic gatable clock which can gate and ungate it's ouput
> @@ -148,3 +151,84 @@ struct clk *clk_register_gate(struct device *dev,
> const char *name,
>       return clk;
>  }
> +
> +#ifdef CONFIG_OF
> +/**
> + * of_clock_gating_control_setup() - Setup function for clock gate control
> + *   This is a helper for using clk-gate from OF device tree. It allocates
> + *   a common lock for a base register and creates the individual
> clk-gates.
> + */
> +void __init of_clock_gating_control_setup(struct device_node *np)
> +{
> +    struct device_node *child;
> +    const char *pclk_name;
> +    void __iomem *base;
> +    spinlock_t *lockp;
> +    unsigned int rnum;
> +    u64 addr;
> +
> +    pclk_name = of_clk_get_parent_name(np, 0);
> +    if (!pclk_name) {
> +        pr_debug("%s: unable to get parent clock for %s\n",
> +            __func__, np->full_name);
> +        return;
> +    }
> +
> +    lockp = kzalloc(sizeof(spinlock_t), GFP_KERNEL);
> +    if (!lockp) {
> +        pr_debug("%s: unable to allocate spinlock for %s\n",
> +             __func__, np->full_name);
> +        return;
> +    }
> +
> +    spin_lock_init(lockp);
> +    base = of_iomap(np, 0);
> +    rnum = sizeof(resource_size_t) * 8;
> +    addr = of_translate_address(np, of_get_property(np, "reg", NULL));
> +
> +    pr_debug("create clock gate control %s\n", np->full_name);
> +
> +    for_each_child_of_node(np, child) {
> +        struct clk *cg;
> +        const char *cg_name;
> +        const char *cg_pclk_name;
> +        u32 propval[2];
> +        unsigned int rbit;
> +
> +        if (of_property_read_u32_array(child, "reg", propval, 2)) {
> +            pr_debug("%s: wrong #reg on %s\n",
> +                 __func__, child->full_name);
> +            continue;
> +        }
> +
> +        rbit = propval[0];
> +        if (rbit >= rnum) {
> +            pr_debug("%s: bit position of %s exceeds resources\n",
> +                 __func__, child->full_name);
> +            continue;
> +        }
> +
> +        cg_pclk_name = of_clk_get_parent_name(child, 0);
> +        if (!pclk_name)
> +            cg_pclk_name = pclk_name;
> +
> +        if (of_property_read_string(child, "clock-output-names",
> +                        &cg_name)) {
> +            unsigned int nlen = 4 + 16 + strlen(child->name);
> +            char *name = kzalloc(nlen+1, GFP_KERNEL);
> +            if (!name)
> +                continue;
> +            snprintf(name, nlen, "%u@%llx.%s", rbit,
> +                 (unsigned long long)addr, child->name);
> +            cg_name = name;
> +        }
> +
> +        pr_debug("  create clock gate: %s\n", cg_name);
> +
> +        cg = clk_register_gate(NULL, cg_name, cg_pclk_name, 0,
> +                       base, rbit, propval[1], lockp);
> +        if (cg)
> +            of_clk_add_provider(child, of_clk_src_simple_get, cg);
> +    }
> +}
> +#endif
> diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
> index b97f61e..499eac2 100644
> --- a/include/linux/clk-provider.h
> +++ b/include/linux/clk-provider.h
> @@ -205,6 +205,8 @@ struct clk *clk_register_gate(struct device *dev,
> const char *name,
>          void __iomem *reg, u8 bit_idx,
>          u8 clk_gate_flags, spinlock_t *lock);
>  +void of_clock_gating_control_setup(struct device_node *np);
> +
>  /**
>   * struct clk_divider - adjustable divider clock
>   *

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/