From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: [PATCH v6 01/17] pwm: Add PWM framework support Date: Tue, 10 Apr 2012 17:06:24 +0200 Message-ID: <1334070400-25013-2-git-send-email-thierry.reding@avionic-design.de> References: <1334070400-25013-1-git-send-email-thierry.reding@avionic-design.de> Return-path: In-Reply-To: <1334070400-25013-1-git-send-email-thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Cc: Sascha Hauer , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Arnd Bergmann , Matthias Kaehlcke , Kurt Van Dijck , Rob Herring , Grant Likely , Colin Cross , Olof Johansson , Stephen Warren , Richard Purdie , Mark Brown , Mitch Bradley , Mike Frysinger , Eric Miao , Lars-Peter Clausen , Ryan Mallon , Shawn Guo , Bernhard Walle List-Id: linux-tegra@vger.kernel.org From: Sascha Hauer This patch adds framework support for PWM (pulse width modulation) devices. The is a barebone PWM API already in the kernel under include/linux/pwm.h, but it does not allow for multiple drivers as each of them implements the pwm_*() functions. There are other PWM framework patches around from Bill Gatliff. Unlike his framework this one does not change the existing API for PWMs so that this framework can act as a drop in replacement for the existing API. Why another framework? Several people argue that there should not be another framework for PWMs but they should be integrated into one of the existing frameworks like led or hwmon. Unlike these frameworks the PWM framework is agnostic to the purpose of the PWM. In fact, a PWM can drive a LED, but this makes the LED framework a user of a PWM, like already done in leds-pwm.c. The gpio framework also is not suitable for PWMs. Every gpio could be turned into a PWM using timer based toggling, but on the other hand not every PWM hardware device can be turned into a gpio due to the lack of hardware capabilities. This patch does not try to improve the PWM API yet, this could be done in subsequent patches. [thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org: fixup typos, kerneldoc comments] Signed-off-by: Sascha Hauer Acked-by: Kurt Van Dijck Reviewed-by: Arnd Bergmann Reviewed-by: Matthias Kaehlcke Reviewed-by: Mark Brown Reviewed-by: Shawn Guo Signed-off-by: Thierry Reding --- Changes in v6: - some editorial cleanups Changes in v5: - minor cleanups and typo fixes - add some kerneldoc comments Documentation/pwm.txt | 54 ++++++++++++ MAINTAINERS | 6 ++ drivers/Kconfig | 2 + drivers/Makefile | 1 + drivers/pwm/Kconfig | 12 +++ drivers/pwm/Makefile | 1 + drivers/pwm/core.c | 227 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/pwm.h | 38 +++++++++ 8 files changed, 341 insertions(+) create mode 100644 Documentation/pwm.txt create mode 100644 drivers/pwm/Kconfig create mode 100644 drivers/pwm/Makefile create mode 100644 drivers/pwm/core.c diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt new file mode 100644 index 0000000..03e39d1 --- /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 6454433..275db57 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5420,6 +5420,12 @@ S: Maintained F: Documentation/video4linux/README.pvrusb2 F: drivers/media/video/pvrusb2/ +PWM core +M: Sascha Hauer +L: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org +S: Maintained +F: drivers/pwm/ + PXA2xx/PXA3xx SUPPORT M: Eric Miao M: Russell King diff --git a/drivers/Kconfig b/drivers/Kconfig index b3ae9e5..ec094b5 100644 --- a/drivers/Kconfig +++ b/drivers/Kconfig @@ -142,4 +142,6 @@ source "drivers/devfreq/Kconfig" source "drivers/modem_shm/Kconfig" +source "drivers/pwm/Kconfig" + endmenu diff --git a/drivers/Makefile b/drivers/Makefile index 4855a1a..52fe956 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-$(CONFIG_RAPIDIO) += rapidio/ diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig new file mode 100644 index 0000000..93c1052 --- /dev/null +++ b/drivers/pwm/Kconfig @@ -0,0 +1,12 @@ +menuconfig PWM + bool "PWM Support" + help + This enables PWM support through the generic PWM framework. + You only need to enable this, if you also want to enable + one or more of the PWM drivers below. + + If unsure, say N. + +if PWM + +endif diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile new file mode 100644 index 0000000..3469c3d --- /dev/null +++ b/drivers/pwm/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_PWM) += core.o diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c new file mode 100644 index 0000000..0b8a38e --- /dev/null +++ b/drivers/pwm/core.c @@ -0,0 +1,227 @@ +/* + * Generic pwmlib implementation + * + * Copyright (C) 2011 Sascha Hauer + * + * 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 +#include +#include +#include +#include +#include +#include + +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 7c77575..1f308a1 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 */ -- 1.7.9.6 From mboxrd@z Thu Jan 1 00:00:00 1970 From: thierry.reding@avionic-design.de (Thierry Reding) Date: Tue, 10 Apr 2012 17:06:24 +0200 Subject: [PATCH v6 01/17] pwm: Add PWM framework support In-Reply-To: <1334070400-25013-1-git-send-email-thierry.reding@avionic-design.de> References: <1334070400-25013-1-git-send-email-thierry.reding@avionic-design.de> Message-ID: <1334070400-25013-2-git-send-email-thierry.reding@avionic-design.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Sascha Hauer This patch adds framework support for PWM (pulse width modulation) devices. The is a barebone PWM API already in the kernel under include/linux/pwm.h, but it does not allow for multiple drivers as each of them implements the pwm_*() functions. There are other PWM framework patches around from Bill Gatliff. Unlike his framework this one does not change the existing API for PWMs so that this framework can act as a drop in replacement for the existing API. Why another framework? Several people argue that there should not be another framework for PWMs but they should be integrated into one of the existing frameworks like led or hwmon. Unlike these frameworks the PWM framework is agnostic to the purpose of the PWM. In fact, a PWM can drive a LED, but this makes the LED framework a user of a PWM, like already done in leds-pwm.c. The gpio framework also is not suitable for PWMs. Every gpio could be turned into a PWM using timer based toggling, but on the other hand not every PWM hardware device can be turned into a gpio due to the lack of hardware capabilities. This patch does not try to improve the PWM API yet, this could be done in subsequent patches. [thierry.reding at avionic-design.de: fixup typos, kerneldoc comments] Signed-off-by: Sascha Hauer Acked-by: Kurt Van Dijck Reviewed-by: Arnd Bergmann Reviewed-by: Matthias Kaehlcke Reviewed-by: Mark Brown Reviewed-by: Shawn Guo Signed-off-by: Thierry Reding --- Changes in v6: - some editorial cleanups Changes in v5: - minor cleanups and typo fixes - add some kerneldoc comments Documentation/pwm.txt | 54 ++++++++++++ MAINTAINERS | 6 ++ drivers/Kconfig | 2 + drivers/Makefile | 1 + drivers/pwm/Kconfig | 12 +++ drivers/pwm/Makefile | 1 + drivers/pwm/core.c | 227 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/pwm.h | 38 +++++++++ 8 files changed, 341 insertions(+) create mode 100644 Documentation/pwm.txt create mode 100644 drivers/pwm/Kconfig create mode 100644 drivers/pwm/Makefile create mode 100644 drivers/pwm/core.c diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt new file mode 100644 index 0000000..03e39d1 --- /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 6454433..275db57 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -5420,6 +5420,12 @@ S: Maintained F: Documentation/video4linux/README.pvrusb2 F: drivers/media/video/pvrusb2/ +PWM core +M: Sascha Hauer +L: linux-kernel at vger.kernel.org +S: Maintained +F: drivers/pwm/ + PXA2xx/PXA3xx SUPPORT M: Eric Miao M: Russell King diff --git a/drivers/Kconfig b/drivers/Kconfig index b3ae9e5..ec094b5 100644 --- a/drivers/Kconfig +++ b/drivers/Kconfig @@ -142,4 +142,6 @@ source "drivers/devfreq/Kconfig" source "drivers/modem_shm/Kconfig" +source "drivers/pwm/Kconfig" + endmenu diff --git a/drivers/Makefile b/drivers/Makefile index 4855a1a..52fe956 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-$(CONFIG_RAPIDIO) += rapidio/ diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig new file mode 100644 index 0000000..93c1052 --- /dev/null +++ b/drivers/pwm/Kconfig @@ -0,0 +1,12 @@ +menuconfig PWM + bool "PWM Support" + help + This enables PWM support through the generic PWM framework. + You only need to enable this, if you also want to enable + one or more of the PWM drivers below. + + If unsure, say N. + +if PWM + +endif diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile new file mode 100644 index 0000000..3469c3d --- /dev/null +++ b/drivers/pwm/Makefile @@ -0,0 +1 @@ +obj-$(CONFIG_PWM) += core.o diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c new file mode 100644 index 0000000..0b8a38e --- /dev/null +++ b/drivers/pwm/core.c @@ -0,0 +1,227 @@ +/* + * Generic pwmlib implementation + * + * Copyright (C) 2011 Sascha Hauer + * + * 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 +#include +#include +#include +#include +#include +#include + +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 7c77575..1f308a1 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 */ -- 1.7.9.6