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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: Brian Norris <briannorris@chromium.org> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
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‎drivers/pwm/Kconfig

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@@ -147,6 +147,13 @@ config PWM_CRC
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Generic PWM framework driver for Crystalcove (CRC) PMIC based PWM
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control.
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config PWM_CROS_EC
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tristate "ChromeOS EC PWM driver"
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depends on MFD_CROS_EC
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help
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PWM driver for exposing a PWM attached to the ChromeOS Embedded
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Controller.
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config PWM_EP93XX
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tristate "Cirrus Logic EP93xx PWM support"
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depends on ARCH_EP93XX

‎drivers/pwm/Makefile

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@@ -12,6 +12,7 @@ obj-$(CONFIG_PWM_BFIN) += pwm-bfin.o
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obj-$(CONFIG_PWM_BRCMSTB) += pwm-brcmstb.o
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obj-$(CONFIG_PWM_CLPS711X) += pwm-clps711x.o
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obj-$(CONFIG_PWM_CRC) += pwm-crc.o
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obj-$(CONFIG_PWM_CROS_EC) += pwm-cros-ec.o
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obj-$(CONFIG_PWM_EP93XX) += pwm-ep93xx.o
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obj-$(CONFIG_PWM_FSL_FTM) += pwm-fsl-ftm.o
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obj-$(CONFIG_PWM_IMG) += pwm-img.o

‎drivers/pwm/pwm-cros-ec.c

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/*
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* Copyright (C) 2016 Google, Inc
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2, as published by
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* the Free Software Foundation.
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*
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* Expose a PWM controlled by the ChromeOS EC to the host processor.
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*/
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#include <linux/module.h>
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#include <linux/mfd/cros_ec.h>
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#include <linux/mfd/cros_ec_commands.h>
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#include <linux/platform_device.h>
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#include <linux/pwm.h>
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#include <linux/slab.h>
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/**
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* struct cros_ec_pwm_device - Driver data for EC PWM
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*
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* @dev: Device node
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* @ec: Pointer to EC device
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* @chip: PWM controller chip
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*/
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struct cros_ec_pwm_device {
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struct device *dev;
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struct cros_ec_device *ec;
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struct pwm_chip chip;
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};
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static inline struct cros_ec_pwm_device *pwm_to_cros_ec_pwm(struct pwm_chip *c)
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{
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return container_of(c, struct cros_ec_pwm_device, chip);
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}
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static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
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{
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struct {
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struct cros_ec_command msg;
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struct ec_params_pwm_set_duty params;
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} buf;
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struct ec_params_pwm_set_duty *params = &buf.params;
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struct cros_ec_command *msg = &buf.msg;
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memset(&buf, 0, sizeof(buf));
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msg->version = 0;
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msg->command = EC_CMD_PWM_SET_DUTY;
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msg->insize = 0;
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msg->outsize = sizeof(*params);
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params->duty = duty;
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params->pwm_type = EC_PWM_TYPE_GENERIC;
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params->index = index;
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return cros_ec_cmd_xfer_status(ec, msg);
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}
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static int __cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index,
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u32 *result)
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{
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struct {
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struct cros_ec_command msg;
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union {
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struct ec_params_pwm_get_duty params;
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struct ec_response_pwm_get_duty resp;
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};
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} buf;
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struct ec_params_pwm_get_duty *params = &buf.params;
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struct ec_response_pwm_get_duty *resp = &buf.resp;
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struct cros_ec_command *msg = &buf.msg;
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int ret;
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memset(&buf, 0, sizeof(buf));
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msg->version = 0;
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msg->command = EC_CMD_PWM_GET_DUTY;
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msg->insize = sizeof(*params);
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msg->outsize = sizeof(*resp);
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params->pwm_type = EC_PWM_TYPE_GENERIC;
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params->index = index;
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ret = cros_ec_cmd_xfer_status(ec, msg);
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if (result)
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*result = msg->result;
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if (ret < 0)
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return ret;
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return resp->duty;
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}
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static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, u8 index)
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{
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return __cros_ec_pwm_get_duty(ec, index, NULL);
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}
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static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
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struct pwm_state *state)
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{
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struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
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int duty_cycle;
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/* The EC won't let us change the period */
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if (state->period != EC_PWM_MAX_DUTY)
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return -EINVAL;
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/*
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* EC doesn't separate the concept of duty cycle and enabled, but
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* kernel does. Translate.
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*/
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duty_cycle = state->enabled ? state->duty_cycle : 0;
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return cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
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}
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static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
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struct pwm_state *state)
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{
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struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
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int ret;
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ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
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if (ret < 0) {
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dev_err(chip->dev, "error getting initial duty: %d\n", ret);
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return;
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}
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state->enabled = (ret > 0);
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state->period = EC_PWM_MAX_DUTY;
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/* Note that "disabled" and "duty cycle == 0" are treated the same */
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state->duty_cycle = ret;
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}
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static struct pwm_device *
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cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
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{
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struct pwm_device *pwm;
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if (args->args[0] >= pc->npwm)
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return ERR_PTR(-EINVAL);
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pwm = pwm_request_from_chip(pc, args->args[0], NULL);
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if (IS_ERR(pwm))
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return pwm;
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/* The EC won't let us change the period */
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pwm->args.period = EC_PWM_MAX_DUTY;
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return pwm;
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}
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static const struct pwm_ops cros_ec_pwm_ops = {
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.get_state = cros_ec_pwm_get_state,
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.apply = cros_ec_pwm_apply,
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.owner = THIS_MODULE,
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};
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static int cros_ec_num_pwms(struct cros_ec_device *ec)
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{
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int i, ret;
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/* The index field is only 8 bits */
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for (i = 0; i <= U8_MAX; i++) {
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u32 result = 0;
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ret = __cros_ec_pwm_get_duty(ec, i, &result);
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/* We want to parse EC protocol errors */
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if (ret < 0 && !(ret == -EPROTO && result))
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return ret;
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/*
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* We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
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* responses; everything else is treated as an error.
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*/
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if (result == EC_RES_INVALID_COMMAND)
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return -ENODEV;
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else if (result == EC_RES_INVALID_PARAM)
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return i;
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else if (result)
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return -EPROTO;
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}
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return U8_MAX;
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}
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static int cros_ec_pwm_probe(struct platform_device *pdev)
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{
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struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
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struct device *dev = &pdev->dev;
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struct cros_ec_pwm_device *ec_pwm;
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struct pwm_chip *chip;
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int ret;
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if (!ec) {
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dev_err(dev, "no parent EC device\n");
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return -EINVAL;
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}
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ec_pwm = devm_kzalloc(dev, sizeof(*ec_pwm), GFP_KERNEL);
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if (!ec_pwm)
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return -ENOMEM;
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chip = &ec_pwm->chip;
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ec_pwm->ec = ec;
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/* PWM chip */
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chip->dev = dev;
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chip->ops = &cros_ec_pwm_ops;
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chip->of_xlate = cros_ec_pwm_xlate;
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chip->of_pwm_n_cells = 1;
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chip->base = -1;
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ret = cros_ec_num_pwms(ec);
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if (ret < 0) {
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dev_err(dev, "Couldn't find PWMs: %d\n", ret);
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return ret;
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}
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chip->npwm = ret;
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dev_dbg(dev, "Probed %u PWMs\n", chip->npwm);
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ret = pwmchip_add(chip);
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if (ret < 0) {
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dev_err(dev, "cannot register PWM: %d\n", ret);
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return ret;
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}
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platform_set_drvdata(pdev, ec_pwm);
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return ret;
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}
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static int cros_ec_pwm_remove(struct platform_device *dev)
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{
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struct cros_ec_pwm_device *ec_pwm = platform_get_drvdata(dev);
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struct pwm_chip *chip = &ec_pwm->chip;
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return pwmchip_remove(chip);
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}
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#ifdef CONFIG_OF
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static const struct of_device_id cros_ec_pwm_of_match[] = {
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{ .compatible = "google,cros-ec-pwm" },
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{},
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};
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MODULE_DEVICE_TABLE(of, cros_ec_pwm_of_match);
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#endif
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static struct platform_driver cros_ec_pwm_driver = {
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.probe = cros_ec_pwm_probe,
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.remove = cros_ec_pwm_remove,
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.driver = {
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.name = "cros-ec-pwm",
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.of_match_table = of_match_ptr(cros_ec_pwm_of_match),
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},
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};
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module_platform_driver(cros_ec_pwm_driver);
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MODULE_ALIAS("platform:cros-ec-pwm");
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MODULE_DESCRIPTION("ChromeOS EC PWM driver");
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MODULE_LICENSE("GPL v2");

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