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BACKPORT: FROMLIST: pwm: Add support for different PWM output types

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Normally, PWM channels have fixed output until software requests to
change their settings. There are some PWM devices whose outputs can be
changed autonomously according to a predefined pattern programmed in
hardware.

Add support for such devices by adding a new pwm_output_type enum type
to identify these two different PWM types and adding helper functions to
read the PWM output type supported by a PWM.

Bug: 140290585
Link: https://lore.kernel.org/lkml/1568415464-20267-1-git-send-email-gurus@codeaurora.org/
Change-Id: Ie8d61975057c51258e5bde9451ce96be4acdf98b
Signed-off-by: Fenglin Wu <fenglinw@codeaurora.org>
[gurus@codeaurora.org: removed output_pattern, changed output_type sysfs
param to read-only, reworded commit message]
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
This commit is contained in:
Fenglin Wu 2017-12-04 09:56:51 +08:00 committed by Todd Kjos
parent 4233dfd7c0
commit 106a4b85e0
3 changed files with 74 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
drivers/pwm/core.c
View File

@ -282,6 +282,7 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
pwm->pwm = chip->base + i;
pwm->hwpwm = i;
pwm->state.polarity = polarity;
pwm->state.output_type = PWM_OUTPUT_FIXED;
if (chip->ops->get_state)
chip->ops->get_state(chip, pwm, &pwm->state);

25
drivers/pwm/sysfs.c
View File

@ -215,11 +215,35 @@ static ssize_t capture_show(struct device *child,
return sprintf(buf, "%u %u\n", result.period, result.duty_cycle);
}
static ssize_t output_type_show(struct device *child,
struct device_attribute *attr,
char *buf)
{
const struct pwm_device *pwm = child_to_pwm_device(child);
const char *output_type = "unknown";
struct pwm_state state;
pwm_get_state(pwm, &state);
switch (state.output_type) {
case PWM_OUTPUT_FIXED:
output_type = "fixed";
break;
case PWM_OUTPUT_MODULATED:
output_type = "modulated";
break;
default:
break;
}
return snprintf(buf, PAGE_SIZE, "%s\n", output_type);
}
static DEVICE_ATTR_RW(period);
static DEVICE_ATTR_RW(duty_cycle);
static DEVICE_ATTR_RW(enable);
static DEVICE_ATTR_RW(polarity);
static DEVICE_ATTR_RO(capture);
static DEVICE_ATTR_RO(output_type);
static struct attribute *pwm_attrs[] = {
&dev_attr_period.attr,
@ -227,6 +251,7 @@ static struct attribute *pwm_attrs[] = {
&dev_attr_enable.attr,
&dev_attr_polarity.attr,
&dev_attr_capture.attr,
&dev_attr_output_type.attr,
NULL
};
ATTRIBUTE_GROUPS(pwm);

48
include/linux/pwm.h
View File

@ -48,6 +48,17 @@ enum {
PWMF_EXPORTED = 1 << 1,
};
/**
* enum pwm_output_type - output type of the PWM signal
* @PWM_OUTPUT_FIXED: PWM output is fixed until a change request
* @PWM_OUTPUT_MODULATED: PWM output is modulated in hardware
* autonomously with a predefined pattern
*/
enum pwm_output_type {
PWM_OUTPUT_FIXED = 1 << 0,
PWM_OUTPUT_MODULATED = 1 << 1,
};
/*
* struct pwm_state - state of a PWM channel
* @period: PWM period (in nanoseconds)
@ -59,6 +70,7 @@ struct pwm_state {
unsigned int period;
unsigned int duty_cycle;
enum pwm_polarity polarity;
enum pwm_output_type output_type;
bool enabled;
};
@ -144,6 +156,16 @@ static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
return state.polarity;
}
static inline enum pwm_output_type pwm_get_output_type(
const struct pwm_device *pwm)
{
struct pwm_state state;
pwm_get_state(pwm, &state);
return state.output_type;
}
static inline void pwm_get_args(const struct pwm_device *pwm,
struct pwm_args *args)
{
@ -250,6 +272,7 @@ pwm_set_relative_duty_cycle(struct pwm_state *state, unsigned int duty_cycle,
* @get_state: get the current PWM state. This function is only
* called once per PWM device when the PWM chip is
* registered.
* @get_output_type_supported: get the supported output type of this PWM
* @owner: helps prevent removal of modules exporting active PWMs
* @config: configure duty cycles and period length for this PWM
* @set_polarity: configure the polarity of this PWM
@ -265,6 +288,8 @@ struct pwm_ops {
const struct pwm_state *state);
void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state);
int (*get_output_type_supported)(struct pwm_chip *chip,
struct pwm_device *pwm);
struct module *owner;
/* Only used by legacy drivers */
@ -319,6 +344,24 @@ void pwm_free(struct pwm_device *pwm);
int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state);
int pwm_adjust_config(struct pwm_device *pwm);
/**
* pwm_get_output_type_supported() - obtain output type of a PWM device.
* @pwm: PWM device
*
* Returns: output type supported by the PWM device
*/
static inline int pwm_get_output_type_supported(struct pwm_device *pwm)
{
if (!pwm)
return -EINVAL;
if (pwm->chip->ops->get_output_type_supported)
return pwm->chip->ops->get_output_type_supported(pwm->chip,
pwm);
return PWM_OUTPUT_FIXED;
}
/**
* pwm_config() - change a PWM device configuration
* @pwm: PWM device
@ -437,6 +480,11 @@ static inline int pwm_adjust_config(struct pwm_device *pwm)
return -ENOTSUPP;
}
static inline int pwm_get_output_type_supported(struct pwm_device *pwm)
{
return -EINVAL;
}
static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
int period_ns)
{