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Subject[PATCH v3 1/4] clk: add DT clock binding support
Date
From: Grant Likely <grant.likely@secretlab.ca>

Based on work 1st by Ben Herrenschmidt and Jeremy Kerr, then by Grant
Likely, this patch adds support to clk_get to allow drivers to retrieve
clock data from the device tree.

Platforms scan for clocks in DT with of_clk_init and a match table, and
the register a provider through of_clk_add_provider. The provider's
clk_src_get function will be called when a device references the
provider's OF node for a clock reference.

v5 (Rob Herring):
- Move from drivers/of into common clock subsystem
- Squashed "dt/clock: add a simple provider get function" and
"dt/clock: add function to get parent clock name"
- Rebase to 3.4-rc1
- Drop CONFIG_OF_CLOCK and just use CONFIG_OF
- Add missing EXPORT_SYMBOL to various functions
- s/clock-output-name/clock-output-names/
- Define that fixed-clock binding is a single output

v4 (Rob Herring):
- Rework for common clk subsystem
- Add of_clk_get_parent_name function

v3: - Clarified documentation

v2: - fixed errant ';' causing compile error
- Editorial fixes from Shawn Guo
- merged in adding lookup to clkdev
- changed property names to match established convention. After
working with the binding a bit it really made more sense to follow the
lead of 'reg', 'gpios' and 'interrupts' by making the input simply
'clocks' & 'clock-names' instead of 'clock-input-*', and to only use
clock-output* for the producer nodes. (Sorry Shawn, this will mean
you need to change some code, but it should be trivial)
- Add ability to inherit clocks from parent nodes by using an empty
'clock-ranges' property. Useful for busses. I could use some feedback
on the new property name, 'clock-ranges' doesn't feel right to me.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Reviewed-by: Shawn Guo <shawn.guo@freescale.com>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Mike Turquette <mturquette@ti.com>
---
.../devicetree/bindings/clock/clock-bindings.txt | 117 ++++++++++++++++
.../devicetree/bindings/clock/fixed-clock.txt | 21 +++
drivers/clk/clk.c | 140 ++++++++++++++++++++
drivers/clk/clkdev.c | 77 +++++++++++
include/linux/clk-provider.h | 14 ++
include/linux/clk.h | 19 +++
6 files changed, 388 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/clock-bindings.txt
create mode 100644 Documentation/devicetree/bindings/clock/fixed-clock.txt
diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
new file mode 100644
index 0000000..eb65d41
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
@@ -0,0 +1,117 @@
+This binding is a work-in-progress, and are based on some experimental
+work by benh[1].
+
+Sources of clock signal can be represented by any node in the device
+tree. Those nodes are designated as clock providers. Clock consumer
+nodes use a phandle and clock specifier pair to connect clock provider
+outputs to clock inputs. Similar to the gpio specifiers, a clock
+specifier is an array of one more more cells identifying the clock
+output on a device. The length of a clock specifier is defined by the
+value of a #clock-cells property in the clock provider node.
+
+[1] http://patchwork.ozlabs.org/patch/31551/
+
+==Clock providers==
+
+Required properties:
+#clock-cells: Number of cells in a clock specifier; Typically 0 for nodes
+ with a single clock output and 1 for nodes with multiple
+ clock outputs.
+
+Optional properties:
+clock-output-names: Recommended to be a list of strings of clock output signal
+ names indexed by the first cell in the clock specifier.
+ However, the meaning of clock-output-names is domain
+ specific to the clock provider, and is only provided to
+ encourage using the same meaning for the majority of clock
+ providers. This format may not work for clock providers
+ using a complex clock specifier format. In those cases it
+ is recommended to omit this property and create a binding
+ specific names property.
+
+ Clock consumer nodes must never directly reference
+ the provider's clock-output-names property.
+
+For example:
+
+ oscillator {
+ #clock-cells = <1>;
+ clock-output-names = "ckil", "ckih";
+ };
+
+- this node defines a device with two clock outputs, the first named
+ "ckil" and the second named "ckih". Consumer nodes always reference
+ clocks by index. The names should reflect the clock output signal
+ names for the device.
+
+==Clock consumers==
+
+Required properties:
+clocks: List of phandle and clock specifier pairs, one pair
+ for each clock input to the device. Note: if the
+ clock provider specifies '0' for #clock-cells, then
+ only the phandle portion of the pair will appear.
+
+Optional properties:
+clock-names: List of clock input name strings sorted in the same
+ order as the clocks property. Consumers drivers
+ will use clock-names to match clock input names
+ with clocks specifiers.
+clock-ranges: Empty property indicating that child nodes can inherit named
+ clocks from this node. Useful for bus nodes to provide a
+ clock to their children.
+
+For example:
+
+ device {
+ clocks = <&osc 1>, <&ref 0>;
+ clock-names = "baud", "register";
+ };
+
+
+This represents a device with two clock inputs, named "baud" and "register".
+The baud clock is connected to output 1 of the &osc device, and the register
+clock is connected to output 0 of the &ref.
+
+==Example==
+
+ /* external oscillator */
+ osc: oscillator {
+ compatible = "fixed-clock";
+ #clock-cells = <1>;
+ clock-frequency = <32678>;
+ clock-output-names = "osc";
+ };
+
+ /* phase-locked-loop device, generates a higher frequency clock
+ * from the external oscillator reference */
+ pll: pll@4c000 {
+ compatible = "vendor,some-pll-interface"
+ #clock-cells = <1>;
+ clocks = <&osc 0>;
+ clock-names = "ref";
+ reg = <0x4c000 0x1000>;
+ clock-output-names = "pll", "pll-switched";
+ };
+
+ /* UART, using the low frequency oscillator for the baud clock,
+ * and the high frequency switched PLL output for register
+ * clocking */
+ uart@a000 {
+ compatible = "fsl,imx-uart";
+ reg = <0xa000 0x1000>;
+ interrupts = <33>;
+ clocks = <&osc 0>, <&pll 1>;
+ clock-names = "baud", "register";
+ };
+
+This DT fragment defines three devices: an external oscillator to provide a
+low-frequency reference clock, a PLL device to generate a higher frequency
+clock signal, and a UART.
+
+* The oscillator is fixed-frequency, and provides one clock output, named "osc".
+* The PLL is both a clock provider and a clock consumer. It uses the clock
+ signal generated by the external oscillator, and provides two output signals
+ ("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)
diff --git a/Documentation/devicetree/bindings/clock/fixed-clock.txt b/Documentation/devicetree/bindings/clock/fixed-clock.txt
new file mode 100644
index 0000000..0b1fe78
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/fixed-clock.txt
@@ -0,0 +1,21 @@
+Binding for simple fixed-rate clock sources.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "fixed-clock".
+- #clock-cells : from common clock binding; shall be set to 0.
+- clock-frequency : frequency of clock in Hz. Should be a single cell.
+
+Optional properties:
+- gpios : From common gpio binding; gpio connection to clock enable pin.
+- clock-output-names : From common clock binding.
+
+Example:
+ clock {
+ compatible = "fixed-clock";
+ #clock-cells = <0>;
+ clock-frequency = <1000000000>;
+ };
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 687b00d..456f5fb 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -16,6 +16,7 @@
#include <linux/err.h>
#include <linux/list.h>
#include <linux/slab.h>
+#include <linux/of.h>

static DEFINE_SPINLOCK(enable_lock);
static DEFINE_MUTEX(prepare_lock);
@@ -1544,3 +1545,142 @@ int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
return ret;
}
EXPORT_SYMBOL_GPL(clk_notifier_unregister);
+
+#ifdef CONFIG_OF
+/**
+ * struct of_clk_provider - Clock provider registration structure
+ * @link: Entry in global list of clock providers
+ * @node: Pointer to device tree node of clock provider
+ * @get: Get clock callback. Returns NULL or a struct clk for the
+ * given clock specifier
+ * @data: context pointer to be passed into @get callback
+ */
+struct of_clk_provider {
+ struct list_head link;
+
+ struct device_node *node;
+ struct clk *(*get)(struct of_phandle_args *clkspec, void *data);
+ void *data;
+};
+
+static LIST_HEAD(of_clk_providers);
+static DEFINE_MUTEX(of_clk_lock);
+
+struct clk *of_clk_src_simple_get(struct of_phandle_args *clkspec,
+ void *data)
+{
+ return data;
+}
+EXPORT_SYMBOL_GPL(of_clk_src_simple_get);
+
+/**
+ * of_clk_add_provider() - Register a clock provider for a node
+ * @np: Device node pointer associated with clock provider
+ * @clk_src_get: callback for decoding clock
+ * @data: context pointer for @clk_src_get callback.
+ */
+int of_clk_add_provider(struct device_node *np,
+ struct clk *(*clk_src_get)(struct of_phandle_args *clkspec,
+ void *data),
+ void *data)
+{
+ struct of_clk_provider *cp;
+
+ cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL);
+ if (!cp)
+ return -ENOMEM;
+
+ cp->node = of_node_get(np);
+ cp->data = data;
+ cp->get = clk_src_get;
+
+ mutex_lock(&of_clk_lock);
+ list_add(&cp->link, &of_clk_providers);
+ mutex_unlock(&of_clk_lock);
+ pr_debug("Added clock from %s\n", np->full_name);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(of_clk_add_provider);
+
+/**
+ * of_clk_del_provider() - Remove a previously registered clock provider
+ * @np: Device node pointer associated with clock provider
+ */
+void of_clk_del_provider(struct device_node *np)
+{
+ struct of_clk_provider *cp;
+
+ mutex_lock(&of_clk_lock);
+ list_for_each_entry(cp, &of_clk_providers, link) {
+ if (cp->node == np) {
+ list_del(&cp->link);
+ of_node_put(cp->node);
+ kfree(cp);
+ break;
+ }
+ }
+ mutex_unlock(&of_clk_lock);
+}
+EXPORT_SYMBOL_GPL(of_clk_del_provider);
+
+struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec)
+{
+ struct of_clk_provider *provider;
+ struct clk *clk = NULL;
+
+ /* Check if we have such a provider in our array */
+ mutex_lock(&of_clk_lock);
+ list_for_each_entry(provider, &of_clk_providers, link) {
+ if (provider->node == clkspec->np)
+ clk = provider->get(clkspec, provider->data);
+ if (clk)
+ break;
+ }
+ mutex_unlock(&of_clk_lock);
+
+ return clk;
+}
+
+const char *of_clk_get_parent_name(struct device_node *np, int index)
+{
+ struct of_phandle_args clkspec;
+ const char *clk_name;
+ int rc;
+
+ if (index < 0)
+ return NULL;
+
+ rc = of_parse_phandle_with_args(np, "clocks", "#clock-cells", index,
+ &clkspec);
+ if (rc)
+ return NULL;
+
+ if (of_property_read_string_index(clkspec.np, "clock-output-names",
+ clkspec.args_count ? clkspec.args[0] : 0,
+ &clk_name) < 0)
+ clk_name = clkspec.np->name;
+
+ of_node_put(clkspec.np);
+ return clk_name;
+}
+EXPORT_SYMBOL_GPL(of_clk_get_parent_name);
+
+/**
+ * of_clk_init() - Scan and init clock providers from the DT
+ * @matches: array of compatible values and init functions for providers.
+ *
+ * This function scans the device tree for matching clock providers and
+ * calls their initialization functions
+ */
+void __init of_clk_init(const struct of_device_id *matches)
+{
+ struct device_node *np;
+
+ for_each_matching_node(np, matches) {
+ const struct of_device_id *match = of_match_node(matches, np);
+ of_clk_init_cb_t clk_init_cb = match->data;
+ clk_init_cb(np);
+ }
+}
+#endif
diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
index c535cf8..b387435 100644
--- a/drivers/clk/clkdev.c
+++ b/drivers/clk/clkdev.c
@@ -19,10 +19,80 @@
#include <linux/mutex.h>
#include <linux/clk.h>
#include <linux/clkdev.h>
+#include <linux/of.h>

static LIST_HEAD(clocks);
static DEFINE_MUTEX(clocks_mutex);

+#ifdef CONFIG_OF
+struct clk *of_clk_get(struct device_node *np, int index)
+{
+ struct of_phandle_args clkspec;
+ struct clk *clk;
+ int rc;
+
+ if (index < 0)
+ return NULL;
+
+ rc = of_parse_phandle_with_args(np, "clocks", "#clock-cells", index,
+ &clkspec);
+ if (rc)
+ return NULL;
+
+ clk = of_clk_get_from_provider(&clkspec);
+ of_node_put(clkspec.np);
+ return clk;
+}
+EXPORT_SYMBOL(of_clk_get);
+
+/**
+ * of_clk_get_by_name() - Parse and lookup a clock referenced by a device node
+ * @np: pointer to clock consumer node
+ * @name: name of consumer's clock input, or NULL for the first clock reference
+ *
+ * This function parses the clocks and clock-names properties,
+ * and uses them to look up the struct clk from the registered list of clock
+ * providers.
+ */
+struct clk *of_clk_get_by_name(struct device_node *np, const char *name)
+{
+ struct clk *clk = NULL;
+
+ /* Walk up the tree of devices looking for a clock that matches */
+ while (np) {
+ int index = 0;
+
+ /*
+ * For named clocks, first look up the name in the
+ * "clock-names" property. If it cannot be found, then
+ * index will be an error code, and of_clk_get() will fail.
+ */
+ if (name)
+ index = of_property_match_string(np, "clock-names", name);
+ clk = of_clk_get(np, index);
+ if (clk)
+ break;
+ else if (name && index >= 0) {
+ pr_err("ERROR: could not get clock %s:%s(%i)\n",
+ np->full_name, name ? name : "", index);
+ return NULL;
+ }
+
+ /*
+ * No matching clock found on this node. If the parent node
+ * has a "clock-ranges" property, then we can try one of its
+ * clocks.
+ */
+ np = np->parent;
+ if (np && !of_get_property(np, "clock-ranges", NULL))
+ break;
+ }
+
+ return clk;
+}
+EXPORT_SYMBOL(of_clk_get_by_name);
+#endif
+
/*
* Find the correct struct clk for the device and connection ID.
* We do slightly fuzzy matching here:
@@ -83,6 +153,13 @@ EXPORT_SYMBOL(clk_get_sys);
struct clk *clk_get(struct device *dev, const char *con_id)
{
const char *dev_id = dev ? dev_name(dev) : NULL;
+ struct clk *clk;
+
+ if (dev) {
+ clk = of_clk_get_by_name(dev->of_node, con_id);
+ if (clk && __clk_get(clk))
+ return clk;
+ }

return clk_get_sys(dev_id, con_id);
}
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 4a0b483..acfef45 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -334,5 +334,19 @@ void __clk_unprepare(struct clk *clk);
void __clk_reparent(struct clk *clk, struct clk *new_parent);
unsigned long __clk_round_rate(struct clk *clk, unsigned long rate);

+struct of_device_id;
+
+typedef void (*of_clk_init_cb_t)(struct device_node *);
+
+int of_clk_add_provider(struct device_node *np,
+ struct clk *(*clk_src_get)(struct of_phandle_args *args,
+ void *data),
+ void *data);
+void of_clk_del_provider(struct device_node *np);
+struct clk *of_clk_src_simple_get(struct of_phandle_args *clkspec,
+ void *data);
+const char *of_clk_get_parent_name(struct device_node *np, int index);
+void of_clk_init(const struct of_device_id *matches);
+
#endif /* CONFIG_COMMON_CLK */
#endif /* CLK_PROVIDER_H */
diff --git a/include/linux/clk.h b/include/linux/clk.h
index ad5c43e..8b70342 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -310,4 +310,23 @@ struct clk *clk_get_sys(const char *dev_id, const char *con_id);
int clk_add_alias(const char *alias, const char *alias_dev_name, char *id,
struct device *dev);

+struct device_node;
+struct of_phandle_args;
+
+#ifdef CONFIG_OF
+struct clk *of_clk_get(struct device_node *np, int index);
+struct clk *of_clk_get_by_name(struct device_node *np, const char *name);
+struct clk *of_clk_get_from_provider(struct of_phandle_args *clkspec);
+#else
+static inline struct clk *of_clk_get(struct device_node *np, int index)
+{
+ return NULL;
+}
+static inline struct clk *of_clk_get_by_name(struct device_node *np,
+ const char *name)
+{
+ return NULL;
+}
+#endif
+
#endif
--
1.7.9.5


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