[PATCH v5 05/16] pwm: Add device tree support
Thierry Reding
thierry.reding at avionic-design.de
Wed Mar 28 10:33:47 EDT 2012
This patch adds helpers to support device tree bindings for the generic
PWM API. Device tree binding documentation for PWM controllers is also
provided.
Signed-off-by: Thierry Reding <thierry.reding at avionic-design.de>
---
Changes in v5:
- use IS_ENABLED(CONFIG_OF) along with the compiler's DCE instead of
empty implementations of of_pwmchip_add() and of_pwmchip_remove() in
the !OF case
- remove OF_PWM Kconfig symbol and make OF support code conditional on
the OF symbol only
- use "pwms" and "pwm-names" fixed property names
- remove redundant check in of_pwm_simple_xlate()
- use pwm_request_from_chip() instead of pwm_request_from_device()
- integrate OF support with pwm_get() from new patch 4
Changes in v4:
- add OF-specific code removed from patch 2
- make of_node_to_pwmchip() and of_pwm_simple_xlate() static
- rename of_get_named_pwm() to of_pwm_request(), return a struct
pwm_device, get rid of the now unused spec parameter and use the
device_node.name field as the PWM's name
- return a requested struct pwm_device from pwm_chip.of_xlate and
drop the now unused spec parameter
- move OF support code into drivers/pwm/core.c
- used deferred probing if a PWM chip is not available yet
Changes in v2:
- add device tree binding documentation
- add of_xlate to parse controller-specific PWM-specifier
Documentation/devicetree/bindings/pwm/pwm.txt | 53 ++++++++++
drivers/pwm/core.c | 135 ++++++++++++++++++++++++-
include/linux/of_pwm.h | 34 +++++++
include/linux/pwm.h | 6 ++
4 files changed, 226 insertions(+), 2 deletions(-)
create mode 100644 Documentation/devicetree/bindings/pwm/pwm.txt
create mode 100644 include/linux/of_pwm.h
diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt
new file mode 100644
index 0000000..bf2addc
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm.txt
@@ -0,0 +1,53 @@
+Specifying PWM information for devices
+======================================
+
+1) PWM user nodes
+-----------------
+
+PWM users should specify a list of PWM devices that they want to use
+with a property containing a 'pwm-list':
+
+ pwm-list ::= <single-pwm> [pwm-list]
+ single-pwm ::= <pwm-phandle> <pwm-specifier>
+ pwm-phandle : phandle to PWM controller node
+ pwm-specifier : array of #pwm-cells specifying the given PWM
+ (controller specific)
+
+PWM properties should be named "pwms". The exact meaning of each pwms
+property must be documented in the device tree binding for each device.
+An optional property "pwm-names" may contain a list of strings to label
+each of the PWM devices listed in the "pwms" property. If no "pwm-names"
+property is given, the name of the user node will be used as fallback.
+
+The following example could be used to describe a PWM-based backlight
+device:
+
+ pwm: pwm {
+ #pwm-cells = <2>;
+ };
+
+ [...]
+
+ bl: backlight {
+ pwms = <&pwm 0 5000000>;
+ pwm-names = "backlight";
+ };
+
+pwm-specifier typically encodes the chip-relative PWM number and the PWM
+period in nanoseconds. Note that in the example above, specifying the
+"pwm-names" is redundant because the name "backlight" would be used as
+fallback anyway.
+
+2) PWM controller nodes
+-----------------------
+
+PWM controller nodes must specify the number of cells used for the
+specifier using the '#pwm-cells' property.
+
+An example PWM controller might look like this:
+
+ pwm: pwm at 7000a000 {
+ compatible = "nvidia,tegra20-pwm";
+ reg = <0x7000a000 0x100>;
+ #pwm-cells = <2>;
+ };
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 77961e0..c22dd9a 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -20,6 +20,7 @@
*/
#include <linux/module.h>
+#include <linux/of_pwm.h>
#include <linux/pwm.h>
#include <linux/radix-tree.h>
#include <linux/list.h>
@@ -129,6 +130,45 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
return 0;
}
+static struct pwm_device *of_pwm_simple_xlate(struct pwm_chip *pc,
+ const struct of_phandle_args *args)
+{
+ struct pwm_device *pwm;
+
+ if (pc->of_pwm_n_cells < 2)
+ return ERR_PTR(-EINVAL);
+
+ if (args->args[0] >= pc->npwm)
+ return ERR_PTR(-EINVAL);
+
+ pwm = pwm_request_from_chip(pc, args->args[0], NULL);
+ if (IS_ERR(pwm))
+ return ERR_PTR(-ENODEV);
+
+ pwm_set_period(pwm, args->args[1]);
+
+ return pwm;
+}
+
+void of_pwmchip_add(struct pwm_chip *chip)
+{
+ if (!chip->dev || !chip->dev->of_node)
+ return;
+
+ if (!chip->of_xlate) {
+ chip->of_xlate = of_pwm_simple_xlate;
+ chip->of_pwm_n_cells = 2;
+ }
+
+ of_node_get(chip->dev->of_node);
+}
+
+void of_pwmchip_remove(struct pwm_chip *chip)
+{
+ if (chip->dev && chip->dev->of_node)
+ of_node_put(chip->dev->of_node);
+}
+
/**
* pwm_set_chip_data() - set private chip data for a PWM
* @pwm: PWM device
@@ -197,6 +237,9 @@ int pwmchip_add(struct pwm_chip *chip)
INIT_LIST_HEAD(&chip->list);
list_add(&chip->list, &pwm_chips);
+ if (IS_ENABLED(CONFIG_OF))
+ of_pwmchip_add(chip);
+
out:
mutex_unlock(&pwm_lock);
return ret;
@@ -227,6 +270,10 @@ int pwmchip_remove(struct pwm_chip *chip)
}
list_del_init(&chip->list);
+
+ if (IS_ENABLED(CONFIG_OF))
+ of_pwmchip_remove(chip);
+
free_pwms(chip);
out:
@@ -352,6 +399,85 @@ void pwm_disable(struct pwm_device *pwm)
}
EXPORT_SYMBOL_GPL(pwm_disable);
+#ifdef CONFIG_OF
+static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
+{
+ struct pwm_chip *chip;
+
+ mutex_lock(&pwm_lock);
+
+ list_for_each_entry(chip, &pwm_chips, list)
+ if (chip->dev && chip->dev->of_node == np) {
+ mutex_unlock(&pwm_lock);
+ return chip;
+ }
+
+ mutex_unlock(&pwm_lock);
+
+ return ERR_PTR(-EPROBE_DEFER);
+}
+
+/**
+ * of_pwm_request() - request a PWM via the PWM framework
+ * @np: device node to get the PWM from
+ * @index: index of the PWM
+ *
+ * Returns the PWM device parsed from the phandle and index specified in the
+ * "pwms" property of a device tree node or a negative error-code on failure.
+ * Values parsed from the device tree are stored in the returned PWM device
+ * object.
+ */
+struct pwm_device *of_pwm_request(struct device_node *np, int index)
+{
+ struct pwm_device *pwm = NULL;
+ struct of_phandle_args args;
+ struct pwm_chip *pc;
+ int err;
+
+ err = of_parse_phandle_with_args(np, "pwms", "#pwm-cells", index,
+ &args);
+ if (err) {
+ pr_debug("%s(): can't parse \"pwms\" property\n", __func__);
+ return ERR_PTR(err);
+ }
+
+ pc = of_node_to_pwmchip(args.np);
+ if (IS_ERR(pc)) {
+ pr_debug("%s(): PWM chip not found\n", __func__);
+ pwm = ERR_CAST(pc);
+ goto put;
+ }
+
+ if (args.args_count != pc->of_pwm_n_cells) {
+ pr_debug("%s: wrong #pwm-cells for %s\n", np->full_name,
+ args.np->full_name);
+ pwm = ERR_PTR(-EINVAL);
+ goto put;
+ }
+
+ pwm = pc->of_xlate(pc, &args);
+ if (IS_ERR(pwm))
+ goto put;
+
+ err = of_property_read_string_index(np, "pwm-names", index,
+ &pwm->label);
+ if (err < 0) {
+ /*
+ * Fallback to name of user node if the name cannot be parsed
+ * from the "pwm-names" property (e.g. the property doesn't
+ * exist or an error occurred).
+ */
+ pwm->label = np->name;
+ }
+
+put:
+ of_node_put(args.np);
+
+ return pwm;
+}
+EXPORT_SYMBOL(of_pwm_request);
+#endif
+
/**
* pwm_add_table() - register PWM device consumers
* @table: array of consumers to register
@@ -380,8 +506,9 @@ void __init pwm_add_table(struct pwm_lookup *table, size_t num)
* @provider: name of provider PWM chip
* @index: per-chip index of PWM to request
*
- * Look up a PWM chip and a relative index via a table supplied by board setup
- * code (see pwm_add_table()).
+ * Lookup is first attempted using DT. If the device was not instantiated from
+ * a device tree, a PWM chip and a relative index is looked up via a table
+ * supplied by board setup code (see pwm_add_table()).
*
* Once a PWM chip has been found the specified PWM device will be requested
* and is ready to be used.
@@ -394,6 +521,10 @@ struct pwm_device *pwm_get(struct device *dev, const char *consumer)
struct pwm_lookup *p;
unsigned int index;
+ /* look up via DT first */
+ if (dev && dev->of_node)
+ return of_pwm_request(dev->of_node, 0);
+
/*
* We look up the provider in the static table typically provided by
* board setup code. We first try to lookup the consumer device by
diff --git a/include/linux/of_pwm.h b/include/linux/of_pwm.h
new file mode 100644
index 0000000..8c4ed9f
--- /dev/null
+++ b/include/linux/of_pwm.h
@@ -0,0 +1,34 @@
+/*
+ * OF helpers for the PWM API
+ *
+ * Copyright (c) 2011-2012 Avionic Design GmbH
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef __LINUX_OF_PWM_H
+#define __LINUX_OF_PWM_H
+
+#include <linux/err.h>
+#include <linux/pwm.h>
+
+struct device_node;
+
+#ifdef CONFIG_OF
+
+struct pwm_device *of_pwm_request(struct device_node *np, int index);
+
+#else
+
+static inline struct pwm_device *of_pwm_request(struct device_node *np,
+ int index)
+{
+ return ERR_PTR(-ENOSYS);
+}
+
+#endif /* CONFIG_OF */
+
+#endif /* __LINUX_OF_PWM_H */
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index a32d2b7..e19c92a 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -1,6 +1,8 @@
#ifndef __LINUX_PWM_H
#define __LINUX_PWM_H
+#include <linux/of.h>
+
struct pwm_device;
struct seq_file;
@@ -105,6 +107,10 @@ struct pwm_chip {
unsigned int npwm;
struct pwm_device *pwms;
+
+ struct pwm_device * (*of_xlate)(struct pwm_chip *pc,
+ const struct of_phandle_args *args);
+ unsigned int of_pwm_n_cells;
};
int pwm_set_chip_data(struct pwm_device *pwm, void *data);
--
1.7.9.4
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