[PATCH/RFC V6 0/2] clk: Default clk parents and rates assigned in DT

[PATCH/RFC V6 0/2] clk: Default clk parents and rates assigned in DT

[Sylwester Nawrocki]

This patch set adds a DT binding documentation for new 'clock-parents'
and 'clock-rates' DT properties and a helper to parse DT and set the
specified clocks configuration. The helper is now called in the platform
bus before driver probing and by the clock core after registering a clock
provider.

Changes since v5:
 - reverted to the DT binding as sugested by Grant, it should now work
   for both clock suppliers and consumers, similarly as pinctrl hogging;
 - fixed detecting of null phandles (ENOENT error handling);
 - the clocks will now also be attempted to be configured right after
   registering the clock provider, this allows to avoid a call to
   of_clk_set_defaults() in multiple clock provider drivers;
 - dropped of_clk_get_by_property() helper, added of_clk_get_by_clkspec.

Changes since v4:
 - added note explaining how to skip setting parent and rate of a clock,
 - added missing call to of_node_put(),
 - moved of_clk_dev_init() calls to the platform bus,
 - dropped debug traces.

Changes since v3:
 - improved documentation of the DT binding,
 - fixed build errors for !CONFIG_OF, the parsing helpers are only
   compiled in if CONFIG_OF is set.

Changes since v2:
 - code reordering to ensure there is no build errors, the clock
   configuration code moved to a separate file,
 - introduced an 'assigned-clocks' DT node which is supposed to contain
   clocks, clock-parents, clock-rates properties and be child node
   a clock provider node, and a code parsing it called from of_clk_init();
   It's for clocks which are not directly connected to consumer devices.
   An alternative would be to list such assigned clocks in 'clocks'
   property, along with "proper" parent clocks, but then there would
   be phandles in clocks property of a node pointing to itself and it
   would require proper handling in of_clock_init().
   I actually tried it but it looked a bit ugly and chose this time to
   use an extra subnode.

Changes since v1:
 - updated DT binding documentation,
 - dropped the platform bus notifier, the clock setup routine is now
   being called directly from the driver core before a driver probe() call;
   this has an advantage such as all bus types are handled and any errors
   are propagated, so that, for instance a driver probe() can be deferred
   also when resources specified by clock-parents/clock-rates properties
   are not yet available; an alternative would be to let drivers call
   of_clk_device_setup() directly,
 - dropped the patch adding a macro definition for maximum DT property
   name length for now.

This series has been tested on ARM, on Exynos4412 Odroid U3 board.

Sylwester Nawrocki (2):
  clk: Add of_clk_get_by_clkspec() helper
  clk: Add handling of clk parent and rate assigned from DT

 .../devicetree/bindings/clock/clock-bindings.txt   |   32 +++++
 drivers/base/platform.c                            |    5 +
 drivers/clk/Makefile                               |    3 +
 drivers/clk/clk-conf.c                             |  141 ++++++++++++++++++++
 drivers/clk/clk.c                                  |   27 +++-
 drivers/clk/clk.h                                  |    1 +
 drivers/clk/clkdev.c                               |   34 ++++-
 include/linux/clk/clk-conf.h                       |   20 +++
 8 files changed, 253 insertions(+), 10 deletions(-)
 create mode 100644 drivers/clk/clk-conf.c
 create mode 100644 include/linux/clk/clk-conf.h

--
1.7.9.5

[PATCH/RFC V6 1/2] clk: Add of_clk_get_by_clkspec() helper

[Sylwester Nawrocki]

This patch adds of_clk_get_by_clkspec() helper function, which does only
a struct clk lookup from the clock providers. It is used in the subsequent
patch where parsing of a clock from device tree and the lookup from
providers needed to be split.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
---
Changes since v5:
 - dropped of_clk_get_by_property(), added of_clk_get_by_clkspec().

Changes since v4:
 - none.

Changes since v3:
 - added missing 'static inline' to the function stub definition.

Changes since v2:
 - moved the function declaration from drivers/clk/clk.h to
   include/linux/clk.h

Changes since v1:
 - s/of_clk_get_list_entry/of_clk_get_by_property.
---
 drivers/clk/clk.h    |    1 +
 drivers/clk/clkdev.c |   34 +++++++++++++++++++++++++++-------
 2 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/drivers/clk/clk.h b/drivers/clk/clk.h
index 795cc9f..c798138 100644
--- a/drivers/clk/clk.h
+++ b/drivers/clk/clk.h
@@ -10,6 +10,7 @@
  */

 #if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
+struct clk *of_clk_get_by_clkspec(struct of_phandle_args *clkspec);
 struct clk *__of_clk_get_from_provider(struct of_phandle_args *clkspec);
 void of_clk_lock(void);
 void of_clk_unlock(void);
diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c
index a360b2e..f890b90 100644
--- a/drivers/clk/clkdev.c
+++ b/drivers/clk/clkdev.c
@@ -27,6 +27,32 @@ static LIST_HEAD(clocks);
 static DEFINE_MUTEX(clocks_mutex);

 #if defined(CONFIG_OF) && defined(CONFIG_COMMON_CLK)
+
+/**
+ * of_clk_get_by_clkspec() - Lookup a clock form a clock provider
+ * @clkspec: pointer to a clock specifier data structure
+ *
+ * This function looks up a struct clk from the registered list of clock
+ * providers, an input is a clock specifier data structure as returned
+ * from the of_parse_phandle_with_args() function call.
+ */
+struct clk *of_clk_get_by_clkspec(struct of_phandle_args *clkspec)
+{
+	struct clk *clk;
+
+	if (!clkspec)
+		return ERR_PTR(-EINVAL);
+
+	of_clk_lock();
+	clk = __of_clk_get_from_provider(clkspec);
+
+	if (!IS_ERR(clk) && !__clk_get(clk))
+		clk = ERR_PTR(-ENOENT);
+
+	of_clk_unlock();
+	return clk;
+}
+
 struct clk *of_clk_get(struct device_node *np, int index)
 {
 	struct of_phandle_args clkspec;
@@ -41,13 +67,7 @@ struct clk *of_clk_get(struct device_node *np, int index)
 	if (rc)
 		return ERR_PTR(rc);

-	of_clk_lock();
-	clk = __of_clk_get_from_provider(&clkspec);
-
-	if (!IS_ERR(clk) && !__clk_get(clk))
-		clk = ERR_PTR(-ENOENT);
-
-	of_clk_unlock();
+	clk = of_clk_get_by_clkspec(&clkspec);
 	of_node_put(clkspec.np);
 	return clk;
 }
--
1.7.9.5

[PATCH/RFC V6 2/2] clk: Add handling of clk parent and rate assigned from DT

[Sylwester Nawrocki]

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 v5:
 - updated the DT binding description (dropped 'assigned-clocks'
   node);
 - fixed detecting of null phandles (ENOENT error handling);
 - modified of_clk_init() to account for that the clocks property may now
   contain a clock specifier with a phandle that points to our node;

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   |   32 +++++
 drivers/base/platform.c                            |    5 +
 drivers/clk/Makefile                               |    3 +
 drivers/clk/clk-conf.c                             |  141 ++++++++++++++++++++
 drivers/clk/clk.c                                  |   27 +++-
 include/linux/clk/clk-conf.h                       |   20 +++
 6 files changed, 225 insertions(+), 3 deletions(-)
 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..bee649b 100644
--- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
+++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
@@ -132,3 +132,35 @@ 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 default parent clocks
+and clock frequecies. Such a configuration can be specified in a device 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 at 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 consumes
+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 similarly specified in the clock provider node.
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 5b47210..f622733 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -23,6 +23,7 @@
 #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"
@@ -486,6 +487,10 @@ static int platform_drv_probe(struct device *_dev)
 	struct platform_device *dev = to_platform_device(_dev);
 	int ret;

+	ret = of_clk_set_defaults(_dev->of_node, false);
+	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..0bf26d5
--- /dev/null
+++ b/drivers/clk/clk-conf.c
@@ -0,0 +1,141 @@
+/*
+ * 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>
+#include "clk.h"
+
+static int __set_clk_parents(struct device_node *node, bool self_consumer)
+{
+	struct of_phandle_args clkspec;
+	int index, rc, num_parents;
+	struct clk *clk, *pclk;
+
+	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++) {
+		rc = of_parse_phandle_with_args(node, "clock-parents",
+					"#clock-cells",	index, &clkspec);
+		if (rc < 0) {
+			/* skip empty (null) phandles */
+			if (rc == -ENOENT)
+				continue;
+			else
+				return rc;
+		}
+		if (clkspec.np == node && !self_consumer)
+			return 0;
+		pclk = of_clk_get_by_clkspec(&clkspec);
+		if (IS_ERR(pclk)) {
+			pr_warn("clk: couldn't get parent clock %d for %s\n",
+				index, node->full_name);
+			return PTR_ERR(pclk);
+		}
+
+		rc = of_parse_phandle_with_args(node, "clocks",	"#clock-cells",
+						index, &clkspec);
+		if (rc < 0)
+			goto err;
+		if (clkspec.np == node && !self_consumer) {
+			rc = 0;
+			goto err;
+		}
+		clk = of_clk_get_by_clkspec(&clkspec);
+		if (IS_ERR(pclk)) {
+			pr_warn("clk: couldn't get parent clock %d for %s\n",
+				index, node->full_name);
+			rc = PTR_ERR(pclk);
+			goto err;
+		}
+
+		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);
+		clk_put(clk);
+		clk_put(pclk);
+	}
+	return 0;
+err:
+	clk_put(pclk);
+	return rc;
+}
+
+static int __set_clk_rates(struct device_node *node, bool self_consumer)
+{
+	struct of_phandle_args clkspec;
+	struct property	*prop;
+	const __be32 *cur;
+	int rc, index = 0;
+	struct clk *clk;
+	u32 rate;
+
+	of_property_for_each_u32(node, "clock-rates", prop, cur, rate) {
+		if (rate) {
+			rc = of_parse_phandle_with_args(node, "clocks",
+					"#clock-cells",	index, &clkspec);
+			if (rc < 0) {
+				/* skip empty (null) phandles */
+				if (rc == -ENOENT)
+					continue;
+				else
+					return rc;
+			}
+			if (clkspec.np == node && !self_consumer)
+				return 0;
+
+			clk = of_clk_get_by_clkspec(&clkspec);
+			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);
+			clk_put(clk);
+		}
+		index++;
+	}
+	return 0;
+}
+
+/**
+ * of_clk_set_defaults() - parse and set assigned clocks configuration
+ * @node: device node to apply clock settings for
+ * @self_consumer: true to indicate @node may also consume clocks it supplies
+ *
+ * This function parses 'clock-parents' and 'clock-rates' properties and sets
+ * any specified clock parents and rates. The @self_consumer argument should be
+ * set to true if @node may be also a clock supplier of any clock listed in its
+ * 'clocks' or 'clock-parents' properties. Otherwise the functions exits as soon
+ * as it determines the @node is also a supplier of any of the clocks.
+ */
+int of_clk_set_defaults(struct device_node *node, bool self_consumer)
+{
+	int rc;
+
+	if (!node)
+		return 0;
+
+	rc = __set_clk_parents(node, self_consumer);
+	if (rc < 0)
+		return rc;
+
+	return __set_clk_rates(node, self_consumer);
+}
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index dff0373..3a8947d 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>
@@ -2429,6 +2430,7 @@ int of_clk_add_provider(struct device_node *np,
 			void *data)
 {
 	struct of_clk_provider *cp;
+	int ret;

 	cp = kzalloc(sizeof(struct of_clk_provider), GFP_KERNEL);
 	if (!cp)
@@ -2443,7 +2445,11 @@ int of_clk_add_provider(struct device_node *np,
 	mutex_unlock(&of_clk_mutex);
 	pr_debug("Added clock from %s\n", np->full_name);

-	return 0;
+	ret = of_clk_set_defaults(np, true);
+	if (ret < 0)
+		of_clk_del_provider(np);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(of_clk_add_provider);

@@ -2558,10 +2564,23 @@ static LIST_HEAD(clk_provider_list);
  */
 static int parent_ready(struct device_node *np)
 {
+	struct of_phandle_args clkspec;
 	int i = 0;

 	while (true) {
-		struct clk *clk = of_clk_get(np, i);
+		struct clk *clk;
+
+		int rc = of_parse_phandle_with_args(np, "clocks",
+				"#clock-cells", i, &clkspec);
+		if (!rc) {
+			if (clkspec.np == np) {
+				i++;
+				continue;
+			}
+			clk = of_clk_get_by_clkspec(&clkspec);
+		} else {
+			clk = ERR_PTR(rc);
+		}

 		/* this parent is ready we can check the next one */
 		if (!IS_ERR(clk)) {
@@ -2620,7 +2639,10 @@ 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);
+				of_clk_set_defaults(np, true);
+
 				list_del(&clk_provider->node);
 				kfree(clk_provider);
 				is_init_done = true;
@@ -2635,7 +2657,6 @@ 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..0a1f311
--- /dev/null
+++ b/include/linux/clk/clk-conf.h
@@ -0,0 +1,20 @@
+/*
+ * 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_set_defaults(struct device_node *node, bool self_consumer);
+#else
+static inline int of_clk_set_defaults(struct device_node *node,
+				      bool self_consumer)
+{
+	return 0;
+}
+#endif
--
1.7.9.5

[PATCH/RFC V6 2/2] clk: Add handling of clk parent and rate assigned from DT

[Sylwester Nawrocki]

On 19/05/14 19:22, Sylwester Nawrocki wrote:
> @@ -2620,7 +2639,10 @@ 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);
> +				of_clk_set_defaults(np, true);

There is an error in this patch, this line should read:

+				of_clk_set_defaults(clk_provider->np, true);

>  				list_del(&clk_provider->node);
>  				kfree(clk_provider);
>  				is_init_done = true;

[PATCH/RFC V6 2/2] clk: Add handling of clk parent and rate assigned from DT

[Mike Turquette]

Quoting Sylwester Nawrocki (2014-05-19 10:22:51)
> diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> index 700e7aa..bee649b 100644
> --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt
> +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> @@ -132,3 +132,35 @@ 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 default parent clocks
> +and clock frequecies. Such a configuration can be specified in a device node

s/frequecies/frequencies/

> +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 at 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 consumes
> +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 similarly specified in the clock provider node.

Is it worthwhile to show an example of this? I guess the outcome will
depend on whether or not we support "assigned-clocks" property, which I
just revisited in the V5 thread.

Regards,
Mike

[PATCH/RFC V6 2/2] clk: Add handling of clk parent and rate assigned from DT

[Tushar Behera]

On 05/19/2014 10:52 PM, Sylwester Nawrocki wrote:
> 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>

[ ... ]

> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 5b47210..f622733 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -23,6 +23,7 @@
>  #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"
> @@ -486,6 +487,10 @@ static int platform_drv_probe(struct device *_dev)
>  	struct platform_device *dev = to_platform_device(_dev);
>  	int ret;
> 
> +	ret = of_clk_set_defaults(_dev->of_node, false);
> +	if (ret < 0)
> +		return ret;
> +

of_clk_set_defaults() is not getting called when the related driver is
not registered through platform_driver_register().

I came across this issue while testing this patch on peach-pit board with
following dts change. max98090 audio codec driver is registered through
module_i2c_driver().

* arch/arm/boot/dts/exynos5420-peach-pit.dts

&hsi2c_7 {

	status = "okay";

	max98090: codec at 10 {
		compatible = "maxim,max98090";
		reg = <0x10>;
		interrupts = <2 0>;
		interrupt-parent = <&gpx0>;
		pinctrl-names = "default";
		pinctrl-0 = <&max98090_irq>;
+		clocks = <&pmu_system_controller 0>;
+		clock-names = "mclk";
+		clock-parents = <&clock CLK_FIN_PLL>;
+		clock-rates = <24000000>;
	};
};

-- 
Tushar Behera

[PATCH/RFC V6 2/2] clk: Add handling of clk parent and rate assigned from DT

[Sylwester Nawrocki]

On 27/05/14 12:28, Tushar Behera wrote:
> On 05/19/2014 10:52 PM, Sylwester Nawrocki wrote:
>> 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>
> 
> [ ... ]
> 
>> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
>> index 5b47210..f622733 100644
>> --- a/drivers/base/platform.c
>> +++ b/drivers/base/platform.c
>> @@ -23,6 +23,7 @@
>>  #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"
>> @@ -486,6 +487,10 @@ static int platform_drv_probe(struct device *_dev)
>>  	struct platform_device *dev = to_platform_device(_dev);
>>  	int ret;
>>
>> +	ret = of_clk_set_defaults(_dev->of_node, false);
>> +	if (ret < 0)
>> +		return ret;
>> +
> 
> of_clk_set_defaults() is not getting called when the related driver is
> not registered through platform_driver_register().
> 
> I came across this issue while testing this patch on peach-pit board with
> following dts change. max98090 audio codec driver is registered through
> module_i2c_driver().

Yes, that shouldn't be surprising, since now in this RFC the clocks setting
is done only for platform bus devices. Similarly the above call would need to
be added to i2c, amba, spi and maybe other busses.

We just need to be careful to avoid attempting to set up clocks of a clock
provider device before it is probed and actually registers its clocks.

I'm still not sure if we should carry on with this approach or do all the
clocks set up in one place, similarly to disabling unused clocks. I'm afraid
when attempting to set up all clocks at one point in time the clock parent/rate
dependencies may get even more hairy.

The deferred probe mechanism helps to resolve the dependencies when the
clock defaults setting is done before or within a driver probe() call. Either
for clock supplier and consumer nodes or a supplier only.

> * arch/arm/boot/dts/exynos5420-peach-pit.dts
> 
> &hsi2c_7 {
> 
> 	status = "okay";
> 
> 	max98090: codec at 10 {
> 		compatible = "maxim,max98090";
> 		reg = <0x10>;
> 		interrupts = <2 0>;
> 		interrupt-parent = <&gpx0>;
> 		pinctrl-names = "default";
> 		pinctrl-0 = <&max98090_irq>;
> +		clocks = <&pmu_system_controller 0>;
> +		clock-names = "mclk";
> +		clock-parents = <&clock CLK_FIN_PLL>;
> +		clock-rates = <24000000>;
> 	};
> };

--
Regards,
Sylwester