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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2021 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
* For more information on Raspberry Pi's PoE hat see:
* https://www.raspberrypi.org/products/poe-hat/
*
* Limitations:
* - No disable bit, so a disabled PWM is simulated by duty_cycle 0
* - Only normal polarity
* - Fixed 12.5 kHz period
*
* The current period is completed when HW is reconfigured.
*/
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <soc/bcm2835/raspberrypi-firmware.h>
#include <dt-bindings/pwm/raspberrypi,firmware-poe-pwm.h>
#define RPI_PWM_MAX_DUTY 255
#define RPI_PWM_PERIOD_NS 80000 /* 12.5 kHz */
#define RPI_PWM_CUR_DUTY_REG 0x0
struct raspberrypi_pwm {
struct rpi_firmware *firmware;
struct pwm_chip chip;
unsigned int duty_cycle;
};
struct raspberrypi_pwm_prop {
__le32 reg;
__le32 val;
__le32 ret;
} __packed;
static inline
struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
{
return container_of(chip, struct raspberrypi_pwm, chip);
}
static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,
u32 reg, u32 val)
{
struct raspberrypi_pwm_prop msg = {
.reg = cpu_to_le32(reg),
.val = cpu_to_le32(val),
};
int ret;
ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
&msg, sizeof(msg));
if (ret)
return ret;
if (msg.ret)
return -EIO;
return 0;
}
static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,
u32 reg, u32 *val)
{
struct raspberrypi_pwm_prop msg = {
.reg = cpu_to_le32(reg),
};
int ret;
ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
&msg, sizeof(msg));
if (ret)
return ret;
if (msg.ret)
return -EIO;
*val = le32_to_cpu(msg.val);
return 0;
}
static void raspberrypi_pwm_get_state(struct pwm_chip *chip,
struct pwm_device *pwm,
struct pwm_state *state)
{
struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
state->period = RPI_PWM_PERIOD_NS;
state->duty_cycle = DIV_ROUND_UP(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
RPI_PWM_MAX_DUTY);
state->enabled = !!(rpipwm->duty_cycle);
state->polarity = PWM_POLARITY_NORMAL;
}
static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
unsigned int duty_cycle;
int ret;
if (state->period < RPI_PWM_PERIOD_NS ||
state->polarity != PWM_POLARITY_NORMAL)
return -EINVAL;
if (!state->enabled)
duty_cycle = 0;
else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
RPI_PWM_PERIOD_NS);
else
duty_cycle = RPI_PWM_MAX_DUTY;
if (duty_cycle == rpipwm->duty_cycle)
return 0;
ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
duty_cycle);
if (ret) {
dev_err(chip->dev, "Failed to set duty cycle: %pe\n",
ERR_PTR(ret));
return ret;
}
rpipwm->duty_cycle = duty_cycle;
return 0;
}
static const struct pwm_ops raspberrypi_pwm_ops = {
.get_state = raspberrypi_pwm_get_state,
.apply = raspberrypi_pwm_apply,
.owner = THIS_MODULE,
};
static int raspberrypi_pwm_probe(struct platform_device *pdev)
{
struct device_node *firmware_node;
struct device *dev = &pdev->dev;
struct rpi_firmware *firmware;
struct raspberrypi_pwm *rpipwm;
int ret;
firmware_node = of_get_parent(dev->of_node);
if (!firmware_node) {
dev_err(dev, "Missing firmware node\n");
return -ENOENT;
}
firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
of_node_put(firmware_node);
if (!firmware)
return dev_err_probe(dev, -EPROBE_DEFER,
"Failed to get firmware handle\n");
rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);
if (!rpipwm)
return -ENOMEM;
rpipwm->firmware = firmware;
rpipwm->chip.dev = dev;
rpipwm->chip.ops = &raspberrypi_pwm_ops;
rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
&rpipwm->duty_cycle);
if (ret) {
dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));
return ret;
}
return devm_pwmchip_add(dev, &rpipwm->chip);
}
static const struct of_device_id raspberrypi_pwm_of_match[] = {
{ .compatible = "raspberrypi,firmware-poe-pwm", },
{ }
};
MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
static struct platform_driver raspberrypi_pwm_driver = {
.driver = {
.name = "raspberrypi-poe-pwm",
.of_match_table = raspberrypi_pwm_of_match,
},
.probe = raspberrypi_pwm_probe,
};
module_platform_driver(raspberrypi_pwm_driver);
MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
MODULE_LICENSE("GPL v2");
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