Commit d007a00b authored by Thierry Reding's avatar Thierry Reding

Merge branch 'for-4.13/core' into for-next

parents 2ea659a9 93c292ef
======================================
Pulse Width Modulation (PWM) interface Pulse Width Modulation (PWM) interface
======================================
This provides an overview about the Linux PWM interface This provides an overview about the Linux PWM interface
...@@ -16,7 +18,7 @@ Users of the legacy PWM API use unique IDs to refer to PWM devices. ...@@ -16,7 +18,7 @@ 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 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 should instead register a static mapping that can be used to match PWM
consumers to providers, as given in the following example: consumers to providers, as given in the following example::
static struct pwm_lookup board_pwm_lookup[] = { static struct pwm_lookup board_pwm_lookup[] = {
PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL, PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL,
...@@ -40,9 +42,9 @@ New users should use the pwm_get() function and pass to it the consumer ...@@ -40,9 +42,9 @@ 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. Managed device or a consumer name. pwm_put() is used to free the PWM device. Managed
variants of these functions, devm_pwm_get() and devm_pwm_put(), also exist. variants of these functions, devm_pwm_get() and devm_pwm_put(), also exist.
After being requested, a PWM has to be configured using: After being requested, a PWM has to be configured using::
int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state); int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
This API controls both the PWM period/duty_cycle config and the This API controls both the PWM period/duty_cycle config and the
enable/disable state. enable/disable state.
...@@ -72,11 +74,14 @@ interface is provided to use the PWMs from userspace. It is exposed at ...@@ -72,11 +74,14 @@ interface is provided to use the PWMs from userspace. It is exposed at
pwmchipN, where N is the base of the PWM chip. Inside the directory you pwmchipN, where N is the base of the PWM chip. Inside the directory you
will find: will find:
npwm - The number of PWM channels this chip supports (read-only). npwm
The number of PWM channels this chip supports (read-only).
export - Exports a PWM channel for use with sysfs (write-only). export
Exports a PWM channel for use with sysfs (write-only).
unexport - Unexports a PWM channel from sysfs (write-only). unexport
Unexports a PWM channel from sysfs (write-only).
The PWM channels are numbered using a per-chip index from 0 to npwm-1. The PWM channels are numbered using a per-chip index from 0 to npwm-1.
...@@ -84,21 +89,26 @@ When a PWM channel is exported a pwmX directory will be created in the ...@@ -84,21 +89,26 @@ When a PWM channel is exported a pwmX directory will be created in the
pwmchipN directory it is associated with, where X is the number of the pwmchipN directory it is associated with, where X is the number of the
channel that was exported. The following properties will then be available: channel that was exported. The following properties will then be available:
period - The total period of the PWM signal (read/write). period
Value is in nanoseconds and is the sum of the active and inactive The total period of the PWM signal (read/write).
time of the PWM. Value is in nanoseconds and is the sum of the active and inactive
time of the PWM.
duty_cycle - The active time of the PWM signal (read/write). duty_cycle
Value is in nanoseconds and must be less than the period. The active time of the PWM signal (read/write).
Value is in nanoseconds and must be less than the period.
polarity - Changes the polarity of the PWM signal (read/write). polarity
Writes to this property only work if the PWM chip supports changing Changes the polarity of the PWM signal (read/write).
the polarity. The polarity can only be changed if the PWM is not Writes to this property only work if the PWM chip supports changing
enabled. Value is the string "normal" or "inversed". the polarity. The polarity can only be changed if the PWM is not
enabled. Value is the string "normal" or "inversed".
enable - Enable/disable the PWM signal (read/write). enable
0 - disabled Enable/disable the PWM signal (read/write).
1 - enabled
- 0 - disabled
- 1 - enabled
Implementing a PWM driver Implementing a PWM driver
------------------------- -------------------------
......
...@@ -678,7 +678,9 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id) ...@@ -678,7 +678,9 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
pc = of_node_to_pwmchip(args.np); pc = of_node_to_pwmchip(args.np);
if (IS_ERR(pc)) { if (IS_ERR(pc)) {
pr_err("%s(): PWM chip not found\n", __func__); if (PTR_ERR(pc) != -EPROBE_DEFER)
pr_err("%s(): PWM chip not found\n", __func__);
pwm = ERR_CAST(pc); pwm = ERR_CAST(pc);
goto put; goto put;
} }
......
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