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	unsigned int duty_cycle;
31};
32
33struct raspberrypi_pwm_prop {
34	__le32 reg;
35	__le32 val;
36	__le32 ret;
37} __packed;
38
39static inline
40struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
41{
42	return pwmchip_get_drvdata(chip);
43}
44
45static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,
46					u32 reg, u32 val)
47{
48	struct raspberrypi_pwm_prop msg = {
49		.reg = cpu_to_le32(reg),
50		.val = cpu_to_le32(val),
51	};
52	int ret;
53
54	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
55				    &msg, sizeof(msg));
56	if (ret)
57		return ret;
58	if (msg.ret)
59		return -EIO;
60
61	return 0;
62}
63
64static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,
65					u32 reg, u32 *val)
66{
67	struct raspberrypi_pwm_prop msg = {
68		.reg = cpu_to_le32(reg),
69	};
70	int ret;
71
72	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
73				    &msg, sizeof(msg));
74	if (ret)
75		return ret;
76	if (msg.ret)
77		return -EIO;
78
79	*val = le32_to_cpu(msg.val);
80
81	return 0;
82}
83
84static int raspberrypi_pwm_get_state(struct pwm_chip *chip,
85				     struct pwm_device *pwm,
86				     struct pwm_state *state)
87{
88	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
89
90	state->period = RPI_PWM_PERIOD_NS;
91	state->duty_cycle = DIV_ROUND_UP(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
92					 RPI_PWM_MAX_DUTY);
93	state->enabled = !!(rpipwm->duty_cycle);
94	state->polarity = PWM_POLARITY_NORMAL;
95
96	return 0;
97}
98
99static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
100				 const struct pwm_state *state)
101{
102	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
103	unsigned int duty_cycle;
104	int ret;
105
106	if (state->period < RPI_PWM_PERIOD_NS ||
107	    state->polarity != PWM_POLARITY_NORMAL)
108		return -EINVAL;
109
110	if (!state->enabled)
111		duty_cycle = 0;
112	else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
113		duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
114						RPI_PWM_PERIOD_NS);
115	else
116		duty_cycle = RPI_PWM_MAX_DUTY;
117
118	if (duty_cycle == rpipwm->duty_cycle)
119		return 0;
120
121	ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
122					   duty_cycle);
123	if (ret) {
124		dev_err(pwmchip_parent(chip), "Failed to set duty cycle: %pe\n",
125			ERR_PTR(ret));
126		return ret;
127	}
128
129	rpipwm->duty_cycle = duty_cycle;
130
131	return 0;
132}
133
134static const struct pwm_ops raspberrypi_pwm_ops = {
135	.get_state = raspberrypi_pwm_get_state,
136	.apply = raspberrypi_pwm_apply,
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 pwm_chip *chip;
145	struct raspberrypi_pwm *rpipwm;
146	int ret;
147
148	firmware_node = of_get_parent(dev->of_node);
149	if (!firmware_node) {
150		dev_err(dev, "Missing firmware node\n");
151		return -ENOENT;
152	}
153
154	firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
155	of_node_put(firmware_node);
156	if (!firmware)
157		return dev_err_probe(dev, -EPROBE_DEFER,
158				     "Failed to get firmware handle\n");
159
160	chip = devm_pwmchip_alloc(&pdev->dev, RASPBERRYPI_FIRMWARE_PWM_NUM,
161				  sizeof(*rpipwm));
162	if (IS_ERR(chip))
163		return PTR_ERR(chip);
164	rpipwm = raspberrypi_pwm_from_chip(chip);
165
166	rpipwm->firmware = firmware;
167	chip->ops = &raspberrypi_pwm_ops;
168
169	ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
170					   &rpipwm->duty_cycle);
171	if (ret) {
172		dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));
173		return ret;
174	}
175
176	return devm_pwmchip_add(dev, chip);
177}
178
179static const struct of_device_id raspberrypi_pwm_of_match[] = {
180	{ .compatible = "raspberrypi,firmware-poe-pwm", },
181	{ }
182};
183MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
184
185static struct platform_driver raspberrypi_pwm_driver = {
186	.driver = {
187		.name = "raspberrypi-poe-pwm",
188		.of_match_table = raspberrypi_pwm_of_match,
189	},
190	.probe = raspberrypi_pwm_probe,
191};
192module_platform_driver(raspberrypi_pwm_driver);
193
194MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
195MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
196MODULE_LICENSE("GPL v2");
197