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

From: Sylwester Nawrocki
Date: Mon May 19 2014 - 13:26:20 EST

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@xxxxxxxxxxx>
---
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@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@xxxxxxxxxxx>
+ *
+ * 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@xxxxxxxxxxx>
+ *
+ * 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

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