linux/drivers/pwm/pwm-cros-ec.c
Thierry Reding 1db37f9561 pwm: cros-ec: Cache duty cycle value
The ChromeOS embedded controller doesn't differentiate between disabled
and duty cycle being 0. In order not to potentially confuse consumers,
cache the duty cycle and return the cached value instead of the real
value when the PWM is disabled.

Tested-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2019-12-09 10:05:42 +01:00

308 lines
7.1 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Expose a PWM controlled by the ChromeOS EC to the host processor.
*
* Copyright (C) 2016 Google, Inc.
*/
#include <linux/module.h>
#include <linux/platform_data/cros_ec_commands.h>
#include <linux/platform_data/cros_ec_proto.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
/**
* struct cros_ec_pwm_device - Driver data for EC PWM
*
* @dev: Device node
* @ec: Pointer to EC device
* @chip: PWM controller chip
*/
struct cros_ec_pwm_device {
struct device *dev;
struct cros_ec_device *ec;
struct pwm_chip chip;
};
/**
* struct cros_ec_pwm - per-PWM driver data
* @duty_cycle: cached duty cycle
*/
struct cros_ec_pwm {
u16 duty_cycle;
};
static inline struct cros_ec_pwm_device *pwm_to_cros_ec_pwm(struct pwm_chip *c)
{
return container_of(c, struct cros_ec_pwm_device, chip);
}
static int cros_ec_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct cros_ec_pwm *channel;
channel = kzalloc(sizeof(*channel), GFP_KERNEL);
if (!channel)
return -ENOMEM;
pwm_set_chip_data(pwm, channel);
return 0;
}
static void cros_ec_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
kfree(channel);
}
static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
{
struct {
struct cros_ec_command msg;
struct ec_params_pwm_set_duty params;
} __packed buf;
struct ec_params_pwm_set_duty *params = &buf.params;
struct cros_ec_command *msg = &buf.msg;
memset(&buf, 0, sizeof(buf));
msg->version = 0;
msg->command = EC_CMD_PWM_SET_DUTY;
msg->insize = 0;
msg->outsize = sizeof(*params);
params->duty = duty;
params->pwm_type = EC_PWM_TYPE_GENERIC;
params->index = index;
return cros_ec_cmd_xfer_status(ec, msg);
}
static int __cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index,
u32 *result)
{
struct {
struct cros_ec_command msg;
union {
struct ec_params_pwm_get_duty params;
struct ec_response_pwm_get_duty resp;
};
} __packed buf;
struct ec_params_pwm_get_duty *params = &buf.params;
struct ec_response_pwm_get_duty *resp = &buf.resp;
struct cros_ec_command *msg = &buf.msg;
int ret;
memset(&buf, 0, sizeof(buf));
msg->version = 0;
msg->command = EC_CMD_PWM_GET_DUTY;
msg->insize = sizeof(*resp);
msg->outsize = sizeof(*params);
params->pwm_type = EC_PWM_TYPE_GENERIC;
params->index = index;
ret = cros_ec_cmd_xfer_status(ec, msg);
if (result)
*result = msg->result;
if (ret < 0)
return ret;
return resp->duty;
}
static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
{
return __cros_ec_pwm_get_duty(ec, index, NULL);
}
static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
u16 duty_cycle;
int ret;
/* The EC won't let us change the period */
if (state->period != EC_PWM_MAX_DUTY)
return -EINVAL;
/*
* EC doesn't separate the concept of duty cycle and enabled, but
* kernel does. Translate.
*/
duty_cycle = state->enabled ? state->duty_cycle : 0;
ret = cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
if (ret < 0)
return ret;
channel->duty_cycle = state->duty_cycle;
return 0;
}
static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state)
{
struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
int ret;
ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
if (ret < 0) {
dev_err(chip->dev, "error getting initial duty: %d\n", ret);
return;
}
state->enabled = (ret > 0);
state->period = EC_PWM_MAX_DUTY;
/*
* Note that "disabled" and "duty cycle == 0" are treated the same. If
* the cached duty cycle is not zero, used the cached duty cycle. This
* ensures that the configured duty cycle is kept across a disable and
* enable operation and avoids potentially confusing consumers.
*
* For the case of the initial hardware readout, channel->duty_cycle
* will be 0 and the actual duty cycle read from the EC is used.
*/
if (ret == 0 && channel->duty_cycle > 0)
state->duty_cycle = channel->duty_cycle;
else
state->duty_cycle = ret;
}
static struct pwm_device *
cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
{
struct pwm_device *pwm;
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;
/* The EC won't let us change the period */
pwm->args.period = EC_PWM_MAX_DUTY;
return pwm;
}
static const struct pwm_ops cros_ec_pwm_ops = {
.request = cros_ec_pwm_request,
.free = cros_ec_pwm_free,
.get_state = cros_ec_pwm_get_state,
.apply = cros_ec_pwm_apply,
.owner = THIS_MODULE,
};
static int cros_ec_num_pwms(struct cros_ec_device *ec)
{
int i, ret;
/* The index field is only 8 bits */
for (i = 0; i <= U8_MAX; i++) {
u32 result = 0;
ret = __cros_ec_pwm_get_duty(ec, i, &result);
/* We want to parse EC protocol errors */
if (ret < 0 && !(ret == -EPROTO && result))
return ret;
/*
* We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
* responses; everything else is treated as an error.
*/
if (result == EC_RES_INVALID_COMMAND)
return -ENODEV;
else if (result == EC_RES_INVALID_PARAM)
return i;
else if (result)
return -EPROTO;
}
return U8_MAX;
}
static int cros_ec_pwm_probe(struct platform_device *pdev)
{
struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
struct device *dev = &pdev->dev;
struct cros_ec_pwm_device *ec_pwm;
struct pwm_chip *chip;
int ret;
if (!ec) {
dev_err(dev, "no parent EC device\n");
return -EINVAL;
}
ec_pwm = devm_kzalloc(dev, sizeof(*ec_pwm), GFP_KERNEL);
if (!ec_pwm)
return -ENOMEM;
chip = &ec_pwm->chip;
ec_pwm->ec = ec;
/* PWM chip */
chip->dev = dev;
chip->ops = &cros_ec_pwm_ops;
chip->of_xlate = cros_ec_pwm_xlate;
chip->of_pwm_n_cells = 1;
chip->base = -1;
ret = cros_ec_num_pwms(ec);
if (ret < 0) {
dev_err(dev, "Couldn't find PWMs: %d\n", ret);
return ret;
}
chip->npwm = ret;
dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
ret = pwmchip_add(chip);
if (ret < 0) {
dev_err(dev, "cannot register PWM: %d\n", ret);
return ret;
}
platform_set_drvdata(pdev, ec_pwm);
return ret;
}
static int cros_ec_pwm_remove(struct platform_device *dev)
{
struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
struct pwm_chip *chip = &ec_pwm->chip;
return pwmchip_remove(chip);
}
#ifdef CONFIG_OF
static const struct of_device_id cros_ec_pwm_of_match[] = {
{ .compatible = "google,cros-ec-pwm" },
{},
};
MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
#endif
static struct platform_driver cros_ec_pwm_driver = {
.probe = cros_ec_pwm_probe,
.remove = cros_ec_pwm_remove,
.driver = {
.name = "cros-ec-pwm",
.of_match_table = of_match_ptr(cros_ec_pwm_of_match),
},
};
module_platform_driver(cros_ec_pwm_driver);
MODULE_ALIAS("platform:cros-ec-pwm");
MODULE_DESCRIPTION("ChromeOS EC PWM driver");
MODULE_LICENSE("GPL v2");