[PATCH 1/2] pwmlib: add pwm support

Sascha Hauer
2011-01-28T12:21:43Z

The barebone pwm API is present in the kernel for longer.
This patch adds pwmlib support to support dynamically registered
pwms. Porions of this code are inspired by the gpiolib support.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
drivers/Kconfig | 2 +
drivers/Makefile | 1 +
drivers/pwm/Kconfig | 11 +++
drivers/pwm/Makefile | 1 +
drivers/pwm/pwmlib.c | 246 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/pwm.h | 38 ++++++++
6 files changed, 299 insertions(+), 0 deletions(-)
create mode 100644 drivers/pwm/Kconfig
create mode 100644 drivers/pwm/Makefile
create mode 100644 drivers/pwm/pwmlib.c

diff --git a/drivers/Kconfig b/drivers/Kconfig
index 9bfb71f..bb332a6 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -117,4 +117,6 @@ source "drivers/staging/Kconfig"
source "drivers/platform/Kconfig"

source "drivers/clk/Kconfig"
+
+source "drivers/pwm/Kconfig"
endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 7eb35f4..8cd30a5 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -6,6 +6,7 @@
#

obj-y += gpio/
+obj-y += pwm/
obj-$(CONFIG_PCI) += pci/
obj-$(CONFIG_PARISC) += parisc/
obj-$(CONFIG_RAPIDIO) += rapidio/
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
new file mode 100644
index 0000000..04ddbfd
--- /dev/null
+++ b/drivers/pwm/Kconfig
@@ -0,0 +1,11 @@
+menuconfig PWMLIB
+ bool "PWM Support"
+ help
+ This enables PWM support through the generic PWM library.
+ You only need to enable this, if you also want to enable
+ one or more of the PWM drivers below.
+
+ If unsure, say N.
+
+if PWMLIB
+endif
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
new file mode 100644
index 0000000..389c049
--- /dev/null
+++ b/drivers/pwm/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_PWMLIB) += pwmlib.o
diff --git a/drivers/pwm/pwmlib.c b/drivers/pwm/pwmlib.c
new file mode 100644
index 0000000..0d6c4cc
--- /dev/null
+++ b/drivers/pwm/pwmlib.c
@@ -0,0 +1,246 @@
+/*
+ * Generic pwmlib implementation
+ *
+ * Copyright (C) 2011 Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * 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, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; see the file COPYING. If not, write to
+ * the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include <linux/module.h>
+#include <linux/pwm.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+
+struct pwm_device {
+ struct pwm_chip *chip;
+ const char *label;
+ int enabled;
+ unsigned long flags;
+#define FLAG_REQUESTED 0
+#define FLAG_ENABLED 1
+ struct list_head node;
+};
+
+static LIST_HEAD(pwm_list);
+
+static DEFINE_MUTEX(pwm_lock);
+
+static struct pwm_device *find_pwm(int pwm_id)
+{
+ struct pwm_device *pwm;
+
+ list_for_each_entry(pwm, &pwm_list, node) {
+ if (pwm->chip->pwm_id == pwm_id)
+ return pwm;
+ }
+
+ return NULL;
+}
+
+/*
+ * The next pwm id to assign. We do not bother to fill gaps which
+ * occur during dynamic registering/deregistering of pwms, but
+ * instead assign a uniq id to each new pwm.
+ */
+static int next_pwm_id;
+
+/**
+ * pwmchip_reserve() - reserve range of pwms to use with platform code only
+ * @npwms: number of pwms to reserve
+ * Context: platform init
+ *
+ * Maybe called only once. It reserves the first pwm_ids for platform use so
+ * that they can refer to pwm_ids during compile time.
+ */
+int __init pwmchip_reserve(int npwms)
+{
+ if (next_pwm_id)
+ return -EBUSY;
+
+ next_pwm_id = npwms;
+
+ return 0;
+}
+
+/**
+ * pwmchip_add() - register a new pwm
+ * @chip: the pwm
+ *
+ * register a new pwm. pwm->pwm_id must be initialized. if pwm_id < 0 then
+ * a dynamically assigned id will be used, otherwise the id specified,
+ */
+int pwmchip_add(struct pwm_chip *chip)
+{
+ struct pwm_device *pwm;
+ int ret = 0;
+
+ mutex_lock(&pwm_lock);
+
+ if (chip->pwm_id >= 0 && find_pwm(chip->pwm_id)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ pwm = kzalloc(sizeof(*pwm), GFP_KERNEL);
+ if (!pwm) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ pwm->chip = chip;
+
+ if (chip->pwm_id < 0)
+ chip->pwm_id = next_pwm_id++;
+
+ list_add_tail(&pwm->node, &pwm_list);
+out:
+ mutex_unlock(&pwm_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(pwmchip_add);
+
+/**
+ * pwmchip_remove() - remove a pwm
+ * @chip: the pwm
+ *
+ * remove a pwm. This function may return busy if the pwm is still requested.
+ */
+int pwmchip_remove(struct pwm_chip *chip)
+{
+ struct pwm_device *pwm;
+ int ret = 0;
+
+ mutex_lock(&pwm_lock);
+
+ pwm = find_pwm(chip->pwm_id);
+ if (!pwm) {
+ ret = -ENOENT;
+ goto out;
+ }
+
+ if (test_bit(FLAG_REQUESTED, &pwm->flags)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
+ list_del(&pwm->node);
+out:
+ mutex_unlock(&pwm_lock);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(pwmchip_remove);
+
+/*
+ * pwm_request - request a PWM device
+ */
+struct pwm_device *pwm_request(int pwm_id, const char *label)
+{
+ struct pwm_device *pwm;
+ int ret;
+
+ mutex_lock(&pwm_lock);
+
+ pwm = find_pwm(pwm_id);
+ if (!pwm) {
+ pwm = ERR_PTR(-ENOENT);
+ goto out;
+ }
+
+ if (test_bit(FLAG_REQUESTED, &pwm->flags)) {
+ pwm = ERR_PTR(-EBUSY);
+ goto out;
+ }
+
+ if (!try_module_get(pwm->chip->owner)) {
+ pwm = ERR_PTR(-ENODEV);
+ goto out;
+ }
+
+ if (pwm->chip->ops->request) {
+ ret = pwm->chip->ops->request(pwm->chip);
+ if (ret) {
+ pwm = ERR_PTR(ret);
+ goto out_put;
+ }
+ }
+
+ pwm->label = label;
+ set_bit(FLAG_REQUESTED, &pwm->flags);
+
+ goto out;
+
+out_put:
+ module_put(pwm->chip->owner);
+out:
+ mutex_unlock(&pwm_lock);
+
+ return pwm;
+}
+EXPORT_SYMBOL_GPL(pwm_request);
+
+/*
+ * pwm_free - free a PWM device
+ */
+void pwm_free(struct pwm_device *pwm)
+{
+ mutex_lock(&pwm_lock);
+
+ if (!test_and_clear_bit(FLAG_REQUESTED, &pwm->flags)) {
+ pr_warning("PWM device already freed\n");
+ goto out;
+ }
+
+ pwm->label = NULL;
+
+ module_put(pwm->chip->owner);
+out:
+ mutex_unlock(&pwm_lock);
+}
+EXPORT_SYMBOL_GPL(pwm_free);
+
+/*
+ * pwm_config - change a PWM device configuration
+ */
+int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
+{
+ return pwm->chip->ops->config(pwm->chip, duty_ns, period_ns);
+}
+EXPORT_SYMBOL_GPL(pwm_config);
+
+/*
+ * pwm_enable - start a PWM output toggling
+ */
+int pwm_enable(struct pwm_device *pwm)
+{
+ if (!test_and_set_bit(FLAG_ENABLED, &pwm->flags))
+ return pwm->chip->ops->enable(pwm->chip);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pwm_enable);
+
+/*
+ * pwm_disable - stop a PWM output toggling
+ */
+void pwm_disable(struct pwm_device *pwm)
+{
+ if (test_and_clear_bit(FLAG_ENABLED, &pwm->flags))
+ pwm->chip->ops->disable(pwm->chip);
+}
+EXPORT_SYMBOL_GPL(pwm_disable);
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 7c77575..e3e2139 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -28,4 +28,42 @@ int pwm_enable(struct pwm_device *pwm);
*/
void pwm_disable(struct pwm_device *pwm);

+#ifdef CONFIG_PWMLIB
+struct pwm_chip;
+
+/**
+ * struct pwm_ops - PWM operations
+ * @request: optional hook for requesting a PWM
+ * @free: optional hook for freeing a PWM
+ * @config: configure duty cycles and period length for this PWM
+ * @enable: enable PWM output toggling
+ * @disable: disable PWM output toggling
+ */
+struct pwm_ops {
+ int (*request)(struct pwm_chip *chip);
+ void (*free)(struct pwm_chip *chip);
+ int (*config)(struct pwm_chip *chip, int duty_ns,
+ int period_ns);
+ int (*enable)(struct pwm_chip *chip);
+ void (*disable)(struct pwm_chip *chip);
+};
+
+/**
+ * struct pwm_chip - abstract a PWM
+ * @label: for diagnostics
+ * @owner: helps prevent removal of modules exporting active PWMs
+ * @ops: The callbacks for this PWM
+ */
+struct pwm_chip {
+ int pwm_id;
+ const char *label;
+ struct module *owner;
+ struct pwm_ops *ops;
+};
+
+int __must_check pwmchip_reserve(int npwms);
+int pwmchip_add(struct pwm_chip *chip);
+int pwmchip_remove(struct pwm_chip *chip);
+#endif
+
#endif /* __LINUX_PWM_H */
--
1.7.2.3