[PATCH] clk: add specified-rate clock
James Hogan
james.hogan at imgtec.com
Fri May 10 08:44:22 EDT 2013
The frequency of some SoC's external oscillators (for example TZ1090's
XTAL1) are configured by the board using pull-ups/pull-downs of
configuration pins, the logic values of which are automatically latched
on reset and available in an SoC register. Add a generic clock component
and DT bindings to handle this.
It behaves similar to a fixed rate clock (read-only), except it needs
information about a register field (reg, shift, width), and the
clock-frequency is a mapping from register field values to clock
frequencies.
Signed-off-by: James Hogan <james.hogan at imgtec.com>
Cc: Mike Turquette <mturquette at linaro.org>
Cc: Grant Likely <grant.likely at secretlab.ca>
Cc: Rob Herring <rob.herring at calxeda.com>
Cc: Rob Landley <rob at landley.net>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: Linus Walleij <linus.walleij at linaro.org>
Cc: Mark Brown <broonie at opensource.wolfsonmicro.com>
Cc: Lars-Peter Clausen <lars at metafoo.de>
---
.../devicetree/bindings/clock/specified-clock.txt | 39 ++++
drivers/clk/Makefile | 1 +
drivers/clk/clk-specified-rate.c | 201 +++++++++++++++++++++
include/linux/clk-provider.h | 37 ++++
4 files changed, 278 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/specified-clock.txt
create mode 100644 drivers/clk/clk-specified-rate.c
diff --git a/Documentation/devicetree/bindings/clock/specified-clock.txt b/Documentation/devicetree/bindings/clock/specified-clock.txt
new file mode 100644
index 0000000..b36ccf9
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/specified-clock.txt
@@ -0,0 +1,39 @@
+Binding for fixed-rate clock sources with readable configuration.
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : Shall be "specified-clock".
+- #clock-cells : From common clock binding; shall be set to 0.
+- reg : Address of configuration register.
+- shift : Shift of config value field in configuration register.
+- width : Width of config value field in configuration register.
+- clock-frequency : Frequency mapping of clock. Consecutive pairs of cells
+ represent the config value to match and the clock
+ frequency in Hz for that config value.
+
+Optional properties:
+- clock-output-names : From common clock binding.
+
+Example:
+ clock {
+ compatible = "specified-clock";
+ #clock-cells = <0>;
+ reg = <0x02004004 0x4>; /* CR_PERIP_RESET_CFG */
+ shift = <8>; /* FXTAL */
+ width = <4>;
+ clock-frequency =
+ /* FXTAL Frequency */
+ <0 16384000>,
+ <1 19200000>,
+ <2 24000000>,
+ <3 24576000>,
+ <4 26000000>,
+ <5 36000000>,
+ <6 36864000>,
+ <7 38400000>,
+ <8 40000000>;
+ clock-output-names = "xtal1";
+ };
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index e7f7fe9..1343179 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -8,6 +8,7 @@ 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
+obj-$(CONFIG_COMMON_CLK) += clk-specified-rate.o
# SoCs specific
obj-$(CONFIG_ARCH_BCM2835) += clk-bcm2835.o
diff --git a/drivers/clk/clk-specified-rate.c b/drivers/clk/clk-specified-rate.c
new file mode 100644
index 0000000..8f78033
--- /dev/null
+++ b/drivers/clk/clk-specified-rate.c
@@ -0,0 +1,201 @@
+/*
+ * Copyright (C) 2010-2011 Canonical Ltd <jeremy.kerr at canonical.com>
+ * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette at linaro.org>
+ * Copyright (C) 2013 Imagination Technologies Ltd.
+ *
+ * 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.
+ *
+ * Fixed rate clock implementation with rate specified in a register field.
+ * Based on fixed rate clock implementation.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+
+/*
+ * DOC: basic specified-rate clock that cannot gate
+ *
+ * Traits of this clock:
+ * prepare - clk_(un)prepare only ensures parents are prepared
+ * enable - clk_enable only ensures parents are enabled
+ * rate - rate is always a fixed value. No clk_set_rate support
+ * parent - fixed parent. No clk_set_parent support
+ */
+
+#define to_clk_specified_rate(_hw) \
+ container_of(_hw, struct clk_specified_rate, hw)
+
+static unsigned long clk_specified_rate_recalc_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct clk_specified_rate *specified = to_clk_specified_rate(hw);
+ struct clk_specified_rate_entry *entry;
+ u32 val;
+ unsigned int i;
+
+ /* read configuration field */
+ val = readl(specified->reg);
+ val >>= specified->shift;
+ val &= (1 << specified->width) - 1;
+
+ /* match the value in the mapping */
+ for (i = 0; i < specified->num_rates; ++i) {
+ entry = &specified->rates[i];
+ if (val == entry->value)
+ return entry->rate;
+ }
+
+ /* unknown rate! */
+ return 0;
+}
+
+const struct clk_ops clk_specified_rate_ops = {
+ .recalc_rate = clk_specified_rate_recalc_rate,
+};
+EXPORT_SYMBOL_GPL(clk_specified_rate_ops);
+
+/**
+ * clk_register_specified_rate - register specified-rate clock
+ * @dev: device that is registering this clock
+ * @name: name of this clock
+ * @parent_name: name of clock's parent
+ * @flags: framework-specific flags
+ * @reg: config register
+ * @shift: shift into config register of frequency field
+ * @width: width of frequency field in config register
+ * @rates: value->rate mapping entries
+ * @num_rates: number of rates in @rates
+ */
+struct clk *clk_register_specified_rate(struct device *dev, const char *name,
+ const char *parent_name, unsigned long flags,
+ void __iomem *reg, u8 shift, u8 width,
+ struct clk_specified_rate_entry *rates,
+ unsigned long num_rates)
+{
+ struct clk_specified_rate *specified;
+ struct clk *clk;
+ struct clk_init_data init;
+
+ /* allocate specified-rate clock */
+ specified = kzalloc(sizeof(struct clk_specified_rate), GFP_KERNEL);
+ if (!specified) {
+ pr_err("%s(%s): could not allocate specified clk\n",
+ __func__, name);
+ return ERR_PTR(-ENOMEM);
+ }
+
+ init.name = name;
+ init.ops = &clk_specified_rate_ops;
+ init.flags = flags | CLK_IS_BASIC;
+ init.parent_names = (parent_name ? &parent_name : NULL);
+ init.num_parents = (parent_name ? 1 : 0);
+
+ /* struct clk_specified_rate assignments */
+ specified->reg = reg;
+ specified->shift = shift;
+ specified->width = width;
+ specified->rates = rates;
+ specified->num_rates = num_rates;
+ specified->hw.init = &init;
+
+ /* register the clock */
+ clk = clk_register(dev, &specified->hw);
+
+ if (IS_ERR(clk))
+ kfree(specified);
+
+ return clk;
+}
+
+#ifdef CONFIG_OF
+/**
+ * of_specified_clk_setup() - Setup function for specified fixed rate clock
+ */
+void __init of_specified_clk_setup(struct device_node *node)
+{
+ struct clk *clk;
+ const char *clk_name = node->name;
+ u32 shift, width, rate;
+ void __iomem *reg;
+ int len, num_rates, i;
+ struct property *prop;
+ struct clk_specified_rate_entry *rates;
+ const __be32 *p;
+
+ of_property_read_string(node, "clock-output-names", &clk_name);
+
+ if (of_property_read_u32(node, "shift", &shift)) {
+ pr_err("%s(%s): could not read shift property\n",
+ __func__, clk_name);
+ return;
+ }
+
+ if (of_property_read_u32(node, "width", &width)) {
+ pr_err("%s(%s): could not read width property\n",
+ __func__, clk_name);
+ return;
+ }
+
+ reg = of_iomap(node, 0);
+ if (!reg) {
+ pr_err("%s(%s): of_iomap failed\n",
+ __func__, clk_name);
+ return;
+ }
+
+ /* check clock-frequency exists */
+ prop = of_find_property(node, "clock-frequency", &len);
+ if (!prop) {
+ pr_err("%s(%s): could not find clock-frequency property\n",
+ __func__, clk_name);
+ goto err_iounmap;
+ }
+
+ if (len & (sizeof(u32)*2 - 1)) {
+ pr_err("%s(%s): clock-frequency has invalid size of %d bytes\n",
+ __func__, clk_name, len);
+ goto err_iounmap;
+ }
+ num_rates = len / (sizeof(*rates)*2);
+
+ rates = kzalloc(sizeof(*rates)*num_rates, GFP_KERNEL);
+ if (!rates) {
+ pr_err("%s(%s): could not allocate %d rate mapping entries\n",
+ __func__, clk_name, num_rates);
+ goto err_iounmap;
+ }
+
+ /* extract rate mapping */
+ for (i = 0, p = of_prop_next_u32(prop, NULL, &rates[0].value);
+ p;
+ ++i, p = of_prop_next_u32(prop, p, &rates[i].value)) {
+ p = of_prop_next_u32(prop, p, &rate);
+ rates[i].rate = rate;
+ pr_debug("%s(%s): map %u -> %lu Hz\n",
+ __func__, clk_name, rates[i].value, rates[i].rate);
+ }
+
+ clk = clk_register_specified_rate(NULL, clk_name, NULL, CLK_IS_ROOT,
+ reg, shift, width, rates, num_rates);
+ if (IS_ERR(clk))
+ goto err_kfree;
+
+ of_clk_add_provider(node, of_clk_src_simple_get, clk);
+
+ return;
+
+err_kfree:
+ kfree(rates);
+err_iounmap:
+ iounmap(reg);
+}
+EXPORT_SYMBOL_GPL(of_specified_clk_setup);
+CLK_OF_DECLARE(specified_clk, "specified-clock", of_specified_clk_setup);
+#endif
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 1186098..218a406 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -196,6 +196,43 @@ struct clk *clk_register_fixed_rate(struct device *dev, const char *name,
void of_fixed_clk_setup(struct device_node *np);
/**
+ * struct clk_specified_rate_entry - a single possible specified rate
+ * @value: value to match in config register
+ * @rate: rate to use when config register matches @value
+ */
+struct clk_specified_rate_entry {
+ u32 value;
+ unsigned long rate;
+};
+
+/**
+ * struct clk_specified_rate - specified-rate clock
+ * @hw: handle between common and hardware-specific interfaces
+ * @reg: register containing rate specifier field
+ * @shift: shift to rate specifier field
+ * @width: width of rate specifier field
+ * @rates: mapping of specified frequencies
+ * @num_rates: number of rates in array
+ */
+struct clk_specified_rate {
+ struct clk_hw hw;
+ void __iomem *reg;
+ u8 shift;
+ u8 width;
+ struct clk_specified_rate_entry *rates;
+ unsigned int num_rates;
+};
+
+extern const struct clk_ops clk_specified_rate_ops;
+struct clk *clk_register_specified_rate(struct device *dev, const char *name,
+ const char *parent_names, unsigned long flags,
+ void __iomem *reg, u8 shift, u8 width,
+ struct clk_specified_rate_entry *rates,
+ unsigned long num_rates);
+
+void of_specified_clk_setup(struct device_node *np);
+
+/**
* struct clk_gate - gating clock
*
* @hw: handle between common and hardware-specific interfaces
--
1.8.1.2
More information about the linux-arm-kernel
mailing list