8 files changed, 341 insertions, 0 deletions

diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
new file mode 100644
index 00000000000..03e39d14591
--- /dev/null
+++ b/Documentation/pwm.txt
@@ -0,0 +1,54 @@
+Pulse Width Modulation (PWM) interface
+
+This provides an overview about the Linux PWM interface
+
+PWMs are commonly used for controlling LEDs, fans or vibrators in
+cell phones. PWMs with a fixed purpose have no need implementing
+the Linux PWM API (although they could). However, PWMs are often
+found as discrete devices on SoCs which have no fixed purpose. It's
+up to the board designer to connect them to LEDs or fans. To provide
+this kind of flexibility the generic PWM API exists.
+
+Identifying PWMs
+----------------
+
+Users of the legacy PWM API use unique IDs to refer to PWM devices. One
+goal of the new PWM framework is to get rid of this global namespace.
+
+Using PWMs
+----------
+
+A PWM can be requested using pwm_request() and freed after usage with
+pwm_free(). After being requested a PWM has to be configured using
+
+int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
+
+To start/stop toggling the PWM output use pwm_enable()/pwm_disable().
+
+Implementing a PWM driver
+-------------------------
+
+Currently there are two ways to implement pwm drivers. Traditionally
+there only has been the barebone API meaning that each driver has
+to implement the pwm_*() functions itself. This means that it's impossible
+to have multiple PWM drivers in the system. For this reason it's mandatory
+for new drivers to use the generic PWM framework.
+A new PWM device can be added using pwmchip_add() and removed again with
+pwmchip_remove(). pwmchip_add() takes a filled in struct pwm_chip as
+argument which provides the ops and the pwm id to the framework.
+
+Locking
+-------
+
+The PWM core list manipulations are protected by a mutex, so pwm_request()
+and pwm_free() may not be called from an atomic context. Currently the
+PWM core does not enforce any locking to pwm_enable(), pwm_disable() and
+pwm_config(), so the calling context is currently driver specific. This
+is an issue derived from the former barebone API and should be fixed soon.
+
+Helpers
+-------
+
+Currently a PWM can only be configured with period_ns and duty_ns. For several
+use cases freq_hz and duty_percent might be better. Instead of calculating
+this in your driver please consider adding appropriate helpers to the framework.
diff --git a/MAINTAINERS b/MAINTAINERS
index 14bc7071f9d..67d6cb70cb7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5487,6 +5487,12 @@ S:	Maintained
 F:      Documentation/video4linux/README.pvrusb2
 F:      drivers/media/video/pvrusb2/
 
+PWM core
+M:      Sascha Hauer <s.hauer@pengutronix.de>
+L:      linux-kernel@vger.kernel.org
+S:      Maintained
+F:      drivers/pwm/
+
 PXA2xx/PXA3xx SUPPORT
 M:      Eric Miao <eric.y.miao@gmail.com>
 M:      Russell King <linux@arm.linux.org.uk>
diff --git a/drivers/Kconfig b/drivers/Kconfig
index bfc918633fd..805c432c943 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -148,4 +148,6 @@ source "drivers/iio/Kconfig"
 
 source "drivers/vme/Kconfig"
 
+source "drivers/pwm/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 2ba29ffef2c..bd36f09f224 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -8,6 +8,7 @@
 # GPIO must come after pinctrl as gpios may need to mux pins etc
 obj-y                           += pinctrl/
 obj-y                           += gpio/
+obj-y                           += pwm/
 obj-$(CONFIG_PCI)               += pci/
 obj-$(CONFIG_PARISC)            += parisc/
 obj-$(CONFIG_RAPIDIO)           += rapidio/
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
new file mode 100644
index 00000000000..93c1052291a
--- /dev/null
+++ b/drivers/pwm/Kconfig
@@ -0,0 +1,12 @@
+menuconfig PWM
+        bool "PWM Support"
+        help
+          This enables PWM support through the generic PWM framework.
+          You only need to enable this, if you also want to enable
+          one or more of the PWM drivers below.
+
+          If unsure, say N.
+
+if PWM
+
+endif
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
new file mode 100644
index 00000000000..3469c3d28b7
--- /dev/null
+++ b/drivers/pwm/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_PWM)               += core.o
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
new file mode 100644
index 00000000000..0b8a38eca23
--- /dev/null
+++ b/drivers/pwm/core.c
@@ -0,0 +1,227 @@
+/*
+ * 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;
+        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;
+}
+
+/**
+ * pwmchip_add() - register a new PWM chip
+ * @chip: the PWM chip to add
+ */
+int pwmchip_add(struct pwm_chip *chip)
+{
+        struct pwm_device *pwm;
+        int ret = 0;
+
+        pwm = kzalloc(sizeof(*pwm), GFP_KERNEL);
+        if (!pwm)
+                return -ENOMEM;
+
+        pwm->chip = chip;
+
+        mutex_lock(&pwm_lock);
+
+        if (chip->pwm_id >= 0 && _find_pwm(chip->pwm_id)) {
+                ret = -EBUSY;
+                goto out;
+        }
+
+        list_add_tail(&pwm->node, &pwm_list);
+out:
+        mutex_unlock(&pwm_lock);
+
+        if (ret)
+                kfree(pwm);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(pwmchip_add);
+
+/**
+ * pwmchip_remove() - remove a PWM chip
+ * @chip: the PWM chip to remove
+ *
+ * Removes a PWM chip. This function may return busy if the PWM chip provides
+ * a PWM device that 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);
+
+        kfree(pwm);
+out:
+        mutex_unlock(&pwm_lock);
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(pwmchip_remove);
+
+/**
+ * pwm_request() - request a PWM device
+ * @pwm_id: global PWM device index
+ * @label: PWM device label
+ */
+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->ops->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->ops->owner);
+out:
+        mutex_unlock(&pwm_lock);
+
+        return pwm;
+}
+EXPORT_SYMBOL_GPL(pwm_request);
+
+/**
+ * pwm_free() - free a PWM device
+ * @pwm: 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->ops->owner);
+out:
+        mutex_unlock(&pwm_lock);
+}
+EXPORT_SYMBOL_GPL(pwm_free);
+
+/**
+ * pwm_config() - change a PWM device configuration
+ * @pwm: PWM device
+ * @duty_ns: "on" time (in nanoseconds)
+ * @period_ns: duration (in nanoseconds) of one cycle
+ */
+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
+ * @pwm: PWM device
+ */
+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
+ * @pwm: PWM device
+ */
+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 7c775751392..1f308a13105 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_PWM
+struct pwm_chip;
+
+/**
+ * struct pwm_ops - PWM controller 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
+ * @owner: helps prevent removal of modules exporting active PWMs
+ */
+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 module           *owner;
+};
+
+/**
+ * struct pwm_chip - abstract a PWM
+ * @pwm_id: global PWM device index
+ * @label: PWM device label
+ * @ops: controller operations
+ */
+struct pwm_chip {
+        int                     pwm_id;
+        const char              *label;
+        struct pwm_ops          *ops;
+};
+
+int pwmchip_add(struct pwm_chip *chip);
+int pwmchip_remove(struct pwm_chip *chip);
+#endif
+
 #endif /* __LINUX_PWM_H */