[PATCH v4 03/10] pwm: Add device tree support
Thierry Reding
thierry.reding at avionic-design.de
Wed Mar 14 11:56:26 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 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 | 48 ++++++++++
drivers/of/Kconfig | 6 ++
drivers/pwm/core.c | 127 +++++++++++++++++++++++++
include/linux/of_pwm.h | 36 +++++++
include/linux/pwm.h | 8 ++
5 files changed, 225 insertions(+)
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..9421fe7
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm.txt
@@ -0,0 +1,48 @@
+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 "[<name>-]pwms". Exact meaning of each
+pwms property must be documented in the device tree binding for each
+device.
+
+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-specifier typically encodes the chip-relative PWM number and the PWM
+period in nanoseconds.
+
+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/of/Kconfig b/drivers/of/Kconfig
index 6ea51dc..d47b8ee 100644
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -57,6 +57,12 @@ config OF_GPIO
help
OpenFirmware GPIO accessors
+config OF_PWM
+ def_bool y
+ depends on PWM
+ help
+ OpenFirmware PWM accessors
+
config OF_I2C
def_tristate I2C
depends on I2C && !SPARC
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 74dd295..c600606 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>
@@ -121,6 +122,75 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
return 0;
}
+#ifdef CONFIG_OF_PWM
+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);
+}
+
+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_count < pc->of_pwm_n_cells)
+ return ERR_PTR(-EINVAL);
+
+ if (args->args[0] >= pc->npwm)
+ return ERR_PTR(-EINVAL);
+
+ pwm = pwm_request_from_device(pc->dev, 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);
+}
+#else
+static inline void of_pwmchip_add(struct pwm_chip *pc)
+{
+}
+
+static inline void of_pwmchip_remove(struct pwm_chip *pc)
+{
+}
+#endif /* CONFIG_OF_PWM */
+
/**
* pwm_set_chip_data - set private chip data for a PWM
* @pwm: PWM device
@@ -184,6 +254,7 @@ int pwmchip_add(struct pwm_chip *chip)
INIT_LIST_HEAD(&chip->list);
list_add(&chip->list, &pwm_chips);
+ of_pwmchip_add(chip);
out:
mutex_unlock(&pwm_lock);
@@ -215,6 +286,7 @@ int pwmchip_remove(struct pwm_chip *chip)
}
list_del_init(&chip->list);
+ of_pwmchip_remove(chip);
free_pwms(chip);
out:
@@ -364,6 +436,61 @@ void pwm_disable(struct pwm_device *pwm)
}
EXPORT_SYMBOL_GPL(pwm_disable);
+#ifdef CONFIG_OF
+/**
+ * of_pwm_request() - request a PWM via the PWM framework
+ * @np: device node to get the PWM from
+ * @propname: property name containing PWM specifier(s)
+ * @index: index of the PWM
+ *
+ * Returns the PWM device parsed from the phandle specified in the given
+ * property of a device tree node or NULL 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,
+ const char *propname, 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, propname, "#pwm-cells", index,
+ &args);
+ if (err) {
+ pr_debug("%s(): can't parse property \"%s\"\n", __func__,
+ propname);
+ 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;
+
+ pwm->label = np->name;
+
+put:
+ of_node_put(args.np);
+
+ return pwm;
+}
+EXPORT_SYMBOL(of_pwm_request);
+#endif
+
#ifdef CONFIG_DEBUG_FS
static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
{
diff --git a/include/linux/of_pwm.h b/include/linux/of_pwm.h
new file mode 100644
index 0000000..a3a3da7
--- /dev/null
+++ b/include/linux/of_pwm.h
@@ -0,0 +1,36 @@
+/*
+ * 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_PWM
+
+struct pwm_device *of_pwm_request(struct device_node *np,
+ const char *propname, int index);
+
+#else
+
+static inline struct pwm_device *of_pwm_request(struct device_node *np,
+ const char *propname,
+ int index);
+{
+ return ERR_PTR(-ENOSYS);
+}
+
+#endif /* CONFIG_OF_PWM */
+
+#endif /* __LINUX_OF_PWM_H */
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 7261911..7b42336 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;
/*
@@ -102,6 +104,12 @@ struct pwm_chip {
unsigned int npwm;
struct pwm_device *pwms;
+
+#ifdef CONFIG_OF_PWM
+ struct pwm_device * (*of_xlate)(struct pwm_chip *pc,
+ const struct of_phandle_args *args);
+ unsigned int of_pwm_n_cells;
+#endif
};
int pwm_set_chip_data(struct pwm_device *pwm, void *data);
--
1.7.9.4
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