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 <[email protected]> Acked-by: Arnd Bergmann <[email protected]> --- Changes in v6: - don't override error code in of_pwm_simple_xlate() - no longer export of_pwm_request(), only pwm_get() should be used - do a reverse lookup of the index into the "pwms" property by matching the con_id parameter to the "pwm-names" property Changes in v5: - use IS_ENABLED(CONFIG_OF) along with the compiler's DCE instead of empty implementations of of_pwmchip_add() and of_pwmchip_remove() in the !OF case - remove OF_PWM Kconfig symbol and make OF support code conditional on the OF symbol only - use "pwms" and "pwm-names" fixed property names - remove redundant check in of_pwm_simple_xlate() - use pwm_request_from_chip() instead of pwm_request_from_device() - integrate OF support with pwm_get() from new patch 4 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 | 57 ++++++++++ drivers/pwm/core.c | 151 ++++++++++++++++++++++++- include/linux/pwm.h | 6 + 3 files changed, 212 insertions(+), 2 deletions(-) create mode 100644 Documentation/devicetree/bindings/pwm/pwm.txt diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt new file mode 100644 index 0000000..73ec962 --- /dev/null +++ b/Documentation/devicetree/bindings/pwm/pwm.txt @@ -0,0 +1,57 @@ +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 "pwms". The exact meaning of each pwms +property must be documented in the device tree binding for each device. +An optional property "pwm-names" may contain a list of strings to label +each of the PWM devices listed in the "pwms" property. If no "pwm-names" +property is given, the name of the user node will be used as fallback. + +Drivers for devices that use more than a single PWM device can use the +"pwm-names" property to map the name of the PWM device requested by the +pwm_get() call to an index into the list given by the "pwms" property. + +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-names = "backlight"; + }; + +pwm-specifier typically encodes the chip-relative PWM number and the PWM +period in nanoseconds. Note that in the example above, specifying the +"pwm-names" is redundant because the name "backlight" would be used as +fallback anyway. + +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@7000a000 { + compatible = "nvidia,tegra20-pwm"; + reg = <0x7000a000 0x100>; + #pwm-cells = <2>; + }; diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c index 402e466..e5ab7cd 100644 --- a/drivers/pwm/core.c +++ b/drivers/pwm/core.c @@ -129,6 +129,45 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label) return 0; } +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[0] >= pc->npwm) + return ERR_PTR(-EINVAL); + + pwm = pwm_request_from_chip(pc, args->args[0], NULL); + if (IS_ERR(pwm)) + return pwm; + + 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); +} + /** * pwm_set_chip_data() - set private chip data for a PWM * @pwm: PWM device @@ -197,6 +236,9 @@ int pwmchip_add(struct pwm_chip *chip) INIT_LIST_HEAD(&chip->list); list_add(&chip->list, &pwm_chips); + if (IS_ENABLED(CONFIG_OF)) + of_pwmchip_add(chip); + out: mutex_unlock(&pwm_lock); return ret; @@ -227,6 +269,10 @@ int pwmchip_remove(struct pwm_chip *chip) } list_del_init(&chip->list); + + if (IS_ENABLED(CONFIG_OF)) + of_pwmchip_remove(chip); + free_pwms(chip); out: @@ -352,6 +398,102 @@ void pwm_disable(struct pwm_device *pwm) } EXPORT_SYMBOL_GPL(pwm_disable); +#ifdef CONFIG_OF +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); +} + +/** + * of_pwm_request() - request a PWM via the PWM framework + * @np: device node to get the PWM from + * @con_id: consumer name + * + * Returns the PWM device parsed from the phandle and index specified in the + * "pwms" property of a device tree node or a negative error-code on failure. + * Values parsed from the device tree are stored in the returned PWM device + * object. + * + * If con_id is NULL, the first PWM device listed in the "pwms" property will + * be requested. Otherwise the "pwm-names" property is used to do a reverse + * lookup of the PWM index. This also means that the "pwm-names" property + * becomes mandatory for devices that look up the PWM device via the con_id + * parameter. + */ +static struct pwm_device *of_pwm_request(struct device_node *np, + const char *con_id) +{ + struct pwm_device *pwm = NULL; + struct of_phandle_args args; + struct pwm_chip *pc; + int index = 0; + int err; + + if (con_id) { + index = of_property_match_string(np, "pwm-names", con_id); + if (index < 0) + return ERR_PTR(index); + } + + err = of_parse_phandle_with_args(np, "pwms", "#pwm-cells", index, + &args); + if (err) { + pr_debug("%s(): can't parse \"pwms\" property\n", __func__); + 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; + + /* + * If a consumer name was not given, try to look it up from the + * "pwm-names" property if it exists. Otherwise use the name of + * the user device node. + */ + if (!con_id) { + err = of_property_read_string_index(np, "pwm-names", index, + &con_id); + if (err < 0) + con_id = np->name; + } + + pwm->label = con_id; + +put: + of_node_put(args.np); + + return pwm; +} +EXPORT_SYMBOL(of_pwm_request); +#endif + /** * pwm_add_table() - register PWM device consumers * @table: array of consumers to register @@ -374,8 +516,9 @@ void __init pwm_add_table(struct pwm_lookup *table, size_t num) * @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()). + * Lookup is first attempted using DT. If the device was not instantiated from + * a device tree, a PWM chip and a relative index is looked up 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. @@ -390,6 +533,10 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id) unsigned int index; unsigned int match; + /* look up via DT first */ + if (dev && dev->of_node) + return of_pwm_request(dev->of_node, con_id); + /* * We look up the provider in the static table typically provided by * board setup code. We first try to lookup the consumer device by diff --git a/include/linux/pwm.h b/include/linux/pwm.h index 2947a4f..21d076c 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; struct seq_file; @@ -105,6 +107,10 @@ struct pwm_chip { unsigned int npwm; struct pwm_device *pwms; + + struct pwm_device * (*of_xlate)(struct pwm_chip *pc, + const struct of_phandle_args *args); + unsigned int of_pwm_n_cells; }; int pwm_set_chip_data(struct pwm_device *pwm, void *data); -- 1.7.9.6 _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
