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(fw: firmware, tag: RPI_FIRMWARE_SET_POE_HAT_VAL,
55 data: &msg, len: 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(fw: firmware, tag: RPI_FIRMWARE_GET_POE_HAT_VAL,
73 data: &msg, len: 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(firmware: rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
122 val: 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(node: 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(dev: &pdev->dev, firmware_node);
155 of_node_put(node: firmware_node);
156 if (!firmware)
157 return dev_err_probe(dev, err: -EPROBE_DEFER,
158 fmt: "Failed to get firmware handle\n");
159
160 chip = devm_pwmchip_alloc(parent: &pdev->dev, RASPBERRYPI_FIRMWARE_PWM_NUM,
161 sizeof_priv: sizeof(*rpipwm));
162 if (IS_ERR(ptr: chip))
163 return PTR_ERR(ptr: 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(firmware: rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
170 val: &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

source code of linux/drivers/pwm/pwm-raspberrypi-poe.c