Commit 1f0d3bb0 authored by Brian Norris's avatar Brian Norris Committed by Thierry Reding

pwm: Add ChromeOS EC PWM driver

Use the new ChromeOS EC EC_CMD_PWM_{GET,SET}_DUTY commands to control
one or more PWMs attached to the Embedded Controller. Because the EC
allows us to modify the duty cycle (as a percentage, where U16_MAX is
100%) but not the period, we assign the period a fixed value of
EC_PWM_MAX_DUTY and reject all attempts to change it.

This driver supports only device tree at the moment, because that
provides a very flexible way of describing the relationship between PWMs
and their consumer devices (e.g., backlight). On a non-DT system, we'll
probably want to use the non-GENERIC addressing (i.e., we'll need to
make special device instances that will use EC_PWM_TYPE_KB_LIGHT or
EC_PWM_TYPE_DISPLAY_LIGHT), as well as the relatively inflexible
pwm_lookup infrastructure for matching devices. Defer that work for now.
Signed-off-by: 's avatarBrian Norris <briannorris@chromium.org>
Signed-off-by: 's avatarThierry Reding <thierry.reding@gmail.com>
parent 9e60f50b
......@@ -147,6 +147,13 @@ config PWM_CRC
Generic PWM framework driver for Crystalcove (CRC) PMIC based PWM
control.
config PWM_CROS_EC
tristate "ChromeOS EC PWM driver"
depends on MFD_CROS_EC
help
PWM driver for exposing a PWM attached to the ChromeOS Embedded
Controller.
config PWM_EP93XX
tristate "Cirrus Logic EP93xx PWM support"
depends on ARCH_EP93XX
......
......@@ -12,6 +12,7 @@ obj-$(CONFIG_PWM_BFIN) += pwm-bfin.o
obj-$(CONFIG_PWM_BRCMSTB) += pwm-brcmstb.o
obj-$(CONFIG_PWM_CLPS711X) += pwm-clps711x.o
obj-$(CONFIG_PWM_CRC) += pwm-crc.o
obj-$(CONFIG_PWM_CROS_EC) += pwm-cros-ec.o
obj-$(CONFIG_PWM_EP93XX) += pwm-ep93xx.o
obj-$(CONFIG_PWM_FSL_FTM) += pwm-fsl-ftm.o
obj-$(CONFIG_PWM_IMG) += pwm-img.o
......
/*
* Copyright (C) 2016 Google, Inc
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2, as published by
* the Free Software Foundation.
*
* Expose a PWM controlled by the ChromeOS EC to the host processor.
*/
#include <linux/module.h>
#include <linux/mfd/cros_ec.h>
#include <linux/mfd/cros_ec_commands.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;
};
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_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
{
struct {
struct cros_ec_command msg;
struct ec_params_pwm_set_duty params;
} 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;
};
} 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(*params);
msg->outsize = sizeof(*resp);
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,
struct pwm_state *state)
{
struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
int duty_cycle;
/* 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;
return cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
}
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);
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 */
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 = {
.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");
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