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    Subject[PATCH RFC v5 2/2] clk: Add handling of clk parent and rate assigned from DT
    Date
    This patch adds a helper function to configure clock parents and
    rates as specified in clock-parents, clock-rates DT properties
    for a consumer device and a call to it before driver is bound to
    a device.

    Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
    ---
    Changes since v4:
    - added note explaining how to skip setting parent and rate
    of a clock,
    - moved of_clk_dev_init() calls to the platform bus,
    - added missing call to of_node_put(),
    - dropped debug traces.

    Changes since v3:
    - added detailed description of the assigned-clocks subnode,
    - added missing 'static inline' to the function stub definition,
    - clk-conf.c is now excluded when CONFIG_OF is not set,
    - s/of_clk_device_setup/of_clk_device_init.

    Changes since v2:
    - edited in clock-bindings.txt, added note about 'assigned-clocks'
    subnode which may be used to specify "global" clocks configuration
    at a clock provider node,
    - moved of_clk_device_setup() function declaration from clk-provider.h
    to clk-conf.h so required function stubs are available when
    CONFIG_COMMON_CLK is not enabled,

    Changes since v1:
    - the helper function to parse and set assigned clock parents and
    rates made public so it is available to clock providers to call
    directly;
    - dropped the platform bus notification and call of_clk_device_setup()
    is is now called from the driver core, rather than from the
    notification callback;
    - s/of_clk_get_list_entry/of_clk_get_by_property.
    ---
    .../devicetree/bindings/clock/clock-bindings.txt | 44 ++++++++++
    drivers/base/platform.c | 5 ++
    drivers/clk/Makefile | 3 +
    drivers/clk/clk-conf.c | 85 ++++++++++++++++++++
    drivers/clk/clk.c | 12 ++-
    include/linux/clk/clk-conf.h | 19 +++++
    6 files changed, 167 insertions(+), 1 deletion(-)
    create mode 100644 drivers/clk/clk-conf.c
    create mode 100644 include/linux/clk/clk-conf.h

    diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
    index 700e7aa..93513fc 100644
    --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
    +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
    @@ -132,3 +132,47 @@ clock signal, and a UART.
    ("pll" and "pll-switched").
    * The UART has its baud clock connected the external oscillator and its
    register clock connected to the PLL clock (the "pll-switched" signal)
    +
    +==Assigned clock parents and rates==
    +
    +Some platforms require static initial configuration of parts of the clocks
    +controller. Such a configuration can be specified in a clock consumer node
    +through clock-parents and clock-rates DT properties. The former should
    +contain a list of parent clocks in form of phandle and clock specifier pairs,
    +the latter the list of assigned clock frequency values (one cell each).
    +To skip setting parent or rate of a clock its corresponding entry should be
    +set to 0, or can be omitted if it is not followed by any non-zero entry.
    +
    + uart@a000 {
    + compatible = "fsl,imx-uart";
    + reg = <0xa000 0x1000>;
    + ...
    + clocks = <&clkcon 0>, <&clkcon 3>;
    + clock-names = "baud", "mux";
    +
    + clock-parents = <0>, <&pll 1>;
    + clock-rates = <460800>;
    + };
    +
    +In this example the pll is set as parent of "mux" clock and frequency of "baud"
    +clock is specified as 460800 Hz.
    +
    +Configuring a clock's parent and rate through the device node that uses
    +the clock can be done only for clocks that have a single user. Specifying
    +conflicting parent or rate configuration in multiple consumer nodes for
    +a shared clock is forbidden.
    +
    +Configuration of common clocks, which affect multiple consumer devices
    +can be specified in a dedicated 'assigned-clocks' subnode of a clock
    +provider node, e.g.:
    +
    + clkcon {
    + ...
    + #clock-cells = <1>;
    +
    + assigned-clocks {
    + clocks = <&clkcon 16>, <&clkcon 17>;
    + clock-parents = <0>, <&clkcon 1>;
    + clock-rates = <200000>;
    + };
    + };
    diff --git a/drivers/base/platform.c b/drivers/base/platform.c
    index e714709..4b95322 100644
    --- a/drivers/base/platform.c
    +++ b/drivers/base/platform.c
    @@ -22,6 +22,7 @@
    #include <linux/pm_runtime.h>
    #include <linux/idr.h>
    #include <linux/acpi.h>
    +#include <linux/clk/clk-conf.h>

    #include "base.h"
    #include "power/power.h"
    @@ -481,6 +482,10 @@ static int platform_drv_probe(struct device *_dev)
    struct platform_device *dev = to_platform_device(_dev);
    int ret;

    + ret = of_clk_dev_init(_dev->of_node);
    + if (ret < 0)
    + return ret;
    +
    acpi_dev_pm_attach(_dev, true);

    ret = drv->probe(dev);
    diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
    index 5f8a287..45598f7 100644
    --- a/drivers/clk/Makefile
    +++ b/drivers/clk/Makefile
    @@ -8,6 +8,9 @@ obj-$(CONFIG_COMMON_CLK) += clk-fixed-rate.o
    obj-$(CONFIG_COMMON_CLK) += clk-gate.o
    obj-$(CONFIG_COMMON_CLK) += clk-mux.o
    obj-$(CONFIG_COMMON_CLK) += clk-composite.o
    +ifeq ($(CONFIG_OF), y)
    +obj-$(CONFIG_COMMON_CLK) += clk-conf.o
    +endif

    # hardware specific clock types
    # please keep this section sorted lexicographically by file/directory path name
    diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
    new file mode 100644
    index 0000000..c0d4096
    --- /dev/null
    +++ b/drivers/clk/clk-conf.c
    @@ -0,0 +1,85 @@
    +/*
    + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
    + * Sylwester Nawrocki <s.nawrocki@samsung.com>
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License version 2 as
    + * published by the Free Software Foundation.
    + */
    +
    +#include <linux/clk.h>
    +#include <linux/clk-provider.h>
    +#include <linux/device.h>
    +#include <linux/of.h>
    +#include <linux/printk.h>
    +
    +/**
    + * of_clk_dev_init() - parse and set clk configuration assigned to a device
    + * @node: device node to apply the configuration for
    + *
    + * This function parses 'clock-parents' and 'clock-rates' properties and sets
    + * any specified clock parents and rates.
    + */
    +int of_clk_dev_init(struct device_node *node)
    +{
    + struct property *prop;
    + const __be32 *cur;
    + int rc, index, num_parents;
    + struct clk *clk, *pclk;
    + u32 rate;
    +
    + if (!node)
    + return 0;
    +
    + num_parents = of_count_phandle_with_args(node, "clock-parents",
    + "#clock-cells");
    + if (num_parents == -EINVAL)
    + pr_err("clk: invalid value of clock-parents property at %s\n",
    + node->full_name);
    +
    + for (index = 0; index < num_parents; index++) {
    + pclk = of_clk_get_by_property(node, "clock-parents", index);
    + if (IS_ERR(pclk)) {
    + /* skip empty (null) phandles */
    + if (PTR_ERR(pclk) == -ENOENT)
    + continue;
    +
    + pr_warn("clk: couldn't get parent clock %d for %s\n",
    + index, node->full_name);
    +
    + return PTR_ERR(pclk);
    + }
    +
    + clk = of_clk_get(node, index);
    + if (IS_ERR(clk)) {
    + pr_warn("clk: couldn't get clock %d for %s\n",
    + index, node->full_name);
    + return PTR_ERR(clk);
    + }
    +
    + rc = clk_set_parent(clk, pclk);
    + if (rc < 0)
    + pr_err("clk: failed to reparent %s to %s: %d\n",
    + __clk_get_name(clk), __clk_get_name(pclk), rc);
    + }
    +
    + index = 0;
    + of_property_for_each_u32(node, "clock-rates", prop, cur, rate) {
    + if (rate) {
    + clk = of_clk_get(node, index);
    + if (IS_ERR(clk)) {
    + pr_warn("clk: couldn't get clock %d for %s\n",
    + index, node->full_name);
    + return PTR_ERR(clk);
    + }
    +
    + rc = clk_set_rate(clk, rate);
    + if (rc < 0)
    + pr_err("clk: couldn't set %s clock rate: %d\n",
    + __clk_get_name(clk), rc);
    + }
    + index++;
    + }
    +
    + return 0;
    +}
    diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
    index dff0373..0d72a4d 100644
    --- a/drivers/clk/clk.c
    +++ b/drivers/clk/clk.c
    @@ -10,6 +10,7 @@
    */

    #include <linux/clk-private.h>
    +#include <linux/clk/clk-conf.h>
    #include <linux/module.h>
    #include <linux/mutex.h>
    #include <linux/spinlock.h>
    @@ -2620,7 +2621,17 @@ void __init of_clk_init(const struct of_device_id *matches)
    list_for_each_entry_safe(clk_provider, next,
    &clk_provider_list, node) {
    if (force || parent_ready(clk_provider->np)) {
    +
    clk_provider->clk_init_cb(clk_provider->np);
    +
    + /* Set any assigned clock parents and rates */
    + np = of_get_child_by_name(clk_provider->np,
    + "assigned-clocks");
    + if (np) {
    + of_clk_dev_init(np);
    + of_node_put(np);
    + }
    +
    list_del(&clk_provider->node);
    kfree(clk_provider);
    is_init_done = true;
    @@ -2635,7 +2646,6 @@ void __init of_clk_init(const struct of_device_id *matches)
    */
    if (!is_init_done)
    force = true;
    -
    }
    }
    #endif
    diff --git a/include/linux/clk/clk-conf.h b/include/linux/clk/clk-conf.h
    new file mode 100644
    index 0000000..afb4228
    --- /dev/null
    +++ b/include/linux/clk/clk-conf.h
    @@ -0,0 +1,19 @@
    +/*
    + * Copyright (C) 2014 Samsung Electronics Co., Ltd.
    + * Sylwester Nawrocki <s.nawrocki@samsung.com>
    + *
    + * This program is free software; you can redistribute it and/or modify
    + * it under the terms of the GNU General Public License version 2 as
    + * published by the Free Software Foundation.
    + */
    +
    +struct device_node;
    +
    +#if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
    +int of_clk_dev_init(struct device_node *node);
    +#else
    +static inline int of_clk_dev_init(struct device_node *node)
    +{
    + return 0;
    +}
    +#endif
    --
    1.7.9.5


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