1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright 2021 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
  4 * For more information on Raspberry Pi's PoE hat see:
  5 * https://www.raspberrypi.org/products/poe-hat/
  6 *
  7 * Limitations:
  8 *  - No disable bit, so a disabled PWM is simulated by duty_cycle 0
  9 *  - Only normal polarity
 10 *  - Fixed 12.5 kHz period
 11 *
 12 * The current period is completed when HW is reconfigured.
 13 */
 14
 15#include <linux/module.h>
 16#include <linux/of.h>
 17#include <linux/platform_device.h>
 18#include <linux/pwm.h>
 19
 20#include <soc/bcm2835/raspberrypi-firmware.h>
 21#include <dt-bindings/pwm/raspberrypi,firmware-poe-pwm.h>
 22
 23#define RPI_PWM_MAX_DUTY		255
 24#define RPI_PWM_PERIOD_NS		80000 /* 12.5 kHz */
 25
 26#define RPI_PWM_CUR_DUTY_REG		0x0
 27
 28struct raspberrypi_pwm {
 29	struct rpi_firmware *firmware;
 30	struct pwm_chip chip;
 31	unsigned int duty_cycle;
 32};
 33
 34struct raspberrypi_pwm_prop {
 35	__le32 reg;
 36	__le32 val;
 37	__le32 ret;
 38} __packed;
 39
 40static inline
 41struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
 42{
 43	return container_of(chip, struct raspberrypi_pwm, chip);
 44}
 45
 46static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,
 47					u32 reg, u32 val)
 48{
 49	struct raspberrypi_pwm_prop msg = {
 50		.reg = cpu_to_le32(reg),
 51		.val = cpu_to_le32(val),
 52	};
 53	int ret;
 54
 55	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
 56				    &msg, sizeof(msg));
 57	if (ret)
 58		return ret;
 59	if (msg.ret)
 60		return -EIO;
 61
 62	return 0;
 63}
 64
 65static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,
 66					u32 reg, u32 *val)
 67{
 68	struct raspberrypi_pwm_prop msg = {
 69		.reg = reg
 70	};
 71	int ret;
 72
 73	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
 74				    &msg, sizeof(msg));
 75	if (ret)
 76		return ret;
 77	if (msg.ret)
 78		return -EIO;
 79
 80	*val = le32_to_cpu(msg.val);
 81
 82	return 0;
 83}
 84
 85static void raspberrypi_pwm_get_state(struct pwm_chip *chip,
 86				      struct pwm_device *pwm,
 87				      struct pwm_state *state)
 88{
 89	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
 90
 91	state->period = RPI_PWM_PERIOD_NS;
 92	state->duty_cycle = DIV_ROUND_UP(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
 93					 RPI_PWM_MAX_DUTY);
 94	state->enabled = !!(rpipwm->duty_cycle);
 95	state->polarity = PWM_POLARITY_NORMAL;
 96}
 97
 98static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 99				 const struct pwm_state *state)
100{
101	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
102	unsigned int duty_cycle;
103	int ret;
104
105	if (state->period < RPI_PWM_PERIOD_NS ||
106	    state->polarity != PWM_POLARITY_NORMAL)
107		return -EINVAL;
108
109	if (!state->enabled)
110		duty_cycle = 0;
111	else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
112		duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
113						RPI_PWM_PERIOD_NS);
114	else
115		duty_cycle = RPI_PWM_MAX_DUTY;
116
117	if (duty_cycle == rpipwm->duty_cycle)
118		return 0;
119
120	ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
121					   duty_cycle);
122	if (ret) {
123		dev_err(chip->dev, "Failed to set duty cycle: %pe\n",
124			ERR_PTR(ret));
125		return ret;
126	}
127
128	rpipwm->duty_cycle = duty_cycle;
129
130	return 0;
131}
132
133static const struct pwm_ops raspberrypi_pwm_ops = {
134	.get_state = raspberrypi_pwm_get_state,
135	.apply = raspberrypi_pwm_apply,
136	.owner = THIS_MODULE,
137};
138
139static int raspberrypi_pwm_probe(struct platform_device *pdev)
140{
141	struct device_node *firmware_node;
142	struct device *dev = &pdev->dev;
143	struct rpi_firmware *firmware;
144	struct raspberrypi_pwm *rpipwm;
145	int ret;
146
147	firmware_node = of_get_parent(dev->of_node);
148	if (!firmware_node) {
149		dev_err(dev, "Missing firmware node\n");
150		return -ENOENT;
151	}
152
153	firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
154	of_node_put(firmware_node);
155	if (!firmware)
156		return dev_err_probe(dev, -EPROBE_DEFER,
157				     "Failed to get firmware handle\n");
158
159	rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);
160	if (!rpipwm)
161		return -ENOMEM;
162
163	rpipwm->firmware = firmware;
164	rpipwm->chip.dev = dev;
165	rpipwm->chip.ops = &raspberrypi_pwm_ops;
166	rpipwm->chip.base = -1;
167	rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
168
169	platform_set_drvdata(pdev, rpipwm);
170
171	ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
172					   &rpipwm->duty_cycle);
173	if (ret) {
174		dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));
175		return ret;
176	}
177
178	return pwmchip_add(&rpipwm->chip);
179}
180
181static int raspberrypi_pwm_remove(struct platform_device *pdev)
182{
183	struct raspberrypi_pwm *rpipwm = platform_get_drvdata(pdev);
184
185	return pwmchip_remove(&rpipwm->chip);
186}
187
188static const struct of_device_id raspberrypi_pwm_of_match[] = {
189	{ .compatible = "raspberrypi,firmware-poe-pwm", },
190	{ }
191};
192MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
193
194static struct platform_driver raspberrypi_pwm_driver = {
195	.driver = {
196		.name = "raspberrypi-poe-pwm",
197		.of_match_table = raspberrypi_pwm_of_match,
198	},
199	.probe = raspberrypi_pwm_probe,
200	.remove = raspberrypi_pwm_remove,
201};
202module_platform_driver(raspberrypi_pwm_driver);
203
204MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
205MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
206MODULE_LICENSE("GPL v2");