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
28 struct raspberrypi_pwm {
29 struct rpi_firmware *firmware;
30 struct pwm_chip chip;
31 unsigned int duty_cycle;
32 };
33
34 struct raspberrypi_pwm_prop {
35 __le32 reg;
36 __le32 val;
37 __le32 ret;
38 } __packed;
39
40 static inline
raspberrypi_pwm_from_chip(struct pwm_chip * chip)41 struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
42 {
43 return container_of(chip, struct raspberrypi_pwm, chip);
44 }
45
raspberrypi_pwm_set_property(struct rpi_firmware * firmware,u32 reg,u32 val)46 static 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
raspberrypi_pwm_get_property(struct rpi_firmware * firmware,u32 reg,u32 * val)65 static 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
raspberrypi_pwm_get_state(struct pwm_chip * chip,struct pwm_device * pwm,struct pwm_state * state)85 static 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
raspberrypi_pwm_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)98 static 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
133 static 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
raspberrypi_pwm_probe(struct platform_device * pdev)139 static 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 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, &rpipwm->chip);
177 }
178
179 static const struct of_device_id raspberrypi_pwm_of_match[] = {
180 { .compatible = "raspberrypi,firmware-poe-pwm", },
181 { }
182 };
183 MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
184
185 static 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 };
192 module_platform_driver(raspberrypi_pwm_driver);
193
194 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
195 MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
196 MODULE_LICENSE("GPL v2");
197