diff options
| -rw-r--r-- | Documentation/pwm.txt | 27 | ||||
| -rw-r--r-- | drivers/pwm/core.c | 169 | ||||
| -rw-r--r-- | include/linux/pwm.h | 22 |
3 files changed, 199 insertions, 19 deletions
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt index 48f598acdd16..554290ebab94 100644 --- a/Documentation/pwm.txt +++ b/Documentation/pwm.txt @@ -12,14 +12,33 @@ 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. +Users of the legacy PWM API use unique IDs to refer to PWM devices. + +Instead of referring to a PWM device via its unique ID, board setup code +should instead register a static mapping that can be used to match PWM +consumers to providers, as given in the following example: + + static struct pwm_lookup board_pwm_lookup[] = { + PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL), + }; + + static void __init board_init(void) + { + ... + pwm_add_table(board_pwm_lookup, ARRAY_SIZE(board_pwm_lookup)); + ... + } 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 +Legacy users can request a PWM device using pwm_request() and free it +after usage with pwm_free(). + +New users should use the pwm_get() function and pass to it the consumer +device or a consumer name. pwm_put() is used to free the PWM device. + +After being requested a PWM has to be configured using: int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns); diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index aadc1d797449..a2af599e61ae 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -32,6 +32,8 @@ #define MAX_PWMS 1024 +static DEFINE_MUTEX(pwm_lookup_lock); +static LIST_HEAD(pwm_lookup_list); static DEFINE_MUTEX(pwm_lock); static LIST_HEAD(pwm_chips); static DECLARE_BITMAP(allocated_pwms, MAX_PWMS); @@ -80,6 +82,29 @@ static void free_pwms(struct pwm_chip *chip) chip->pwms = NULL; } +static struct pwm_chip *pwmchip_find_by_name(const char *name) +{ + struct pwm_chip *chip; + + if (!name) + return NULL; + + mutex_lock(&pwm_lock); + + list_for_each_entry(chip, &pwm_chips, list) { + const char *chip_name = dev_name(chip->dev); + + if (chip_name && strcmp(chip_name, name) == 0) { + mutex_unlock(&pwm_lock); + return chip; + } + } + + mutex_unlock(&pwm_lock); + + return NULL; +} + static int pwm_device_request(struct pwm_device *pwm, const char *label) { int err; @@ -218,6 +243,8 @@ EXPORT_SYMBOL_GPL(pwmchip_remove); * pwm_request() - request a PWM device * @pwm_id: global PWM device index * @label: PWM device label + * + * This function is deprecated, use pwm_get() instead. */ struct pwm_device *pwm_request(int pwm, const char *label) { @@ -281,24 +308,12 @@ EXPORT_SYMBOL_GPL(pwm_request_from_chip); /** * pwm_free() - free a PWM device * @pwm: PWM device + * + * This function is deprecated, use pwm_put() instead. */ void pwm_free(struct pwm_device *pwm) { - mutex_lock(&pwm_lock); - - if (!test_and_clear_bit(PWMF_REQUESTED, &pwm->flags)) { - pr_warning("PWM device already freed\n"); - goto out; - } - - if (pwm->chip->ops->free) - pwm->chip->ops->free(pwm->chip, pwm); - - pwm->label = NULL; - - module_put(pwm->chip->ops->owner); -out: - mutex_unlock(&pwm_lock); + pwm_put(pwm); } EXPORT_SYMBOL_GPL(pwm_free); @@ -341,6 +356,130 @@ void pwm_disable(struct pwm_device *pwm) } EXPORT_SYMBOL_GPL(pwm_disable); +/** + * pwm_add_table() - register PWM device consumers + * @table: array of consumers to register + * @num: number of consumers in table + */ +void __init pwm_add_table(struct pwm_lookup *table, size_t num) +{ + mutex_lock(&pwm_lookup_lock); + + while (num--) { + list_add_tail(&table->list, &pwm_lookup_list); + table++; + } + + mutex_unlock(&pwm_lookup_lock); +} + +/** + * pwm_get() - look up and request a PWM device + * @dev: device for PWM consumer + * @con_id: consumer name + * + * Look up a PWM chip and a relative index 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. + */ +struct pwm_device *pwm_get(struct device *dev, const char *con_id) +{ + struct pwm_device *pwm = ERR_PTR(-EPROBE_DEFER); + const char *dev_id = dev ? dev_name(dev): NULL; + struct pwm_chip *chip = NULL; + unsigned int best = 0; + struct pwm_lookup *p; + unsigned int index; + unsigned int match; + + /* + * We look up the provider in the static table typically provided by + * board setup code. We first try to lookup the consumer device by + * name. If the consumer device was passed in as NULL or if no match + * was found, we try to find the consumer by directly looking it up + * by name. + * + * If a match is found, the provider PWM chip is looked up by name + * and a PWM device is requested using the PWM device per-chip index. + * + * The lookup algorithm was shamelessly taken from the clock + * framework: + * + * We do slightly fuzzy matching here: + * An entry with a NULL ID is assumed to be a wildcard. + * If an entry has a device ID, it must match + * If an entry has a connection ID, it must match + * Then we take the most specific entry - with the following order + * of precedence: dev+con > dev only > con only. + */ + mutex_lock(&pwm_lookup_lock); + + list_for_each_entry(p, &pwm_lookup_list, list) { + match = 0; + + if (p->dev_id) { + if (!dev_id || strcmp(p->dev_id, dev_id)) + continue; + + match += 2; + } + + if (p->con_id) { + if (!con_id || strcmp(p->con_id, con_id)) + continue; + + match += 1; + } + + if (match > best) { + chip = pwmchip_find_by_name(p->provider); + index = p->index; + + if (match != 3) + best = match; + else + break; + } + } + + if (chip) + pwm = pwm_request_from_chip(chip, index, con_id ?: dev_id); + + mutex_unlock(&pwm_lookup_lock); + + return pwm; +} +EXPORT_SYMBOL_GPL(pwm_get); + +/** + * pwm_put() - release a PWM device + * @pwm: PWM device + */ +void pwm_put(struct pwm_device *pwm) +{ + if (!pwm) + return; + + mutex_lock(&pwm_lock); + + if (!test_and_clear_bit(PWMF_REQUESTED, &pwm->flags)) { + pr_warning("PWM device already freed\n"); + goto out; + } + + if (pwm->chip->ops->free) + pwm->chip->ops->free(pwm->chip, pwm); + + pwm->label = NULL; + + module_put(pwm->chip->ops->owner); +out: + mutex_unlock(&pwm_lock); +} +EXPORT_SYMBOL_GPL(pwm_put); + #ifdef CONFIG_DEBUG_FS static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s) { diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 047cd5351a3b..2947a4fea6ad 100644 --- a/include/linux/pwm.h +++ b/include/linux/pwm.h @@ -115,6 +115,28 @@ int pwmchip_remove(struct pwm_chip *chip); struct pwm_device *pwm_request_from_chip(struct pwm_chip *chip, unsigned int index, const char *label); + +struct pwm_device *pwm_get(struct device *dev, const char *consumer); +void pwm_put(struct pwm_device *pwm); + +struct pwm_lookup { + struct list_head list; + const char *provider; + unsigned int index; + const char *dev_id; + const char *con_id; +}; + +#define PWM_LOOKUP(_provider, _index, _dev_id, _con_id) \ + { \ + .provider = _provider, \ + .index = _index, \ + .dev_id = _dev_id, \ + .con_id = _con_id, \ + } + +void pwm_add_table(struct pwm_lookup *table, size_t num); + #endif #endif /* __LINUX_PWM_H */ |