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
41 struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
42 {
43 	return container_of(chip, struct raspberrypi_pwm, chip);
44 }
45 
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 
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 
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 
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 
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.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
167 
168 	ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
169 					   &rpipwm->duty_cycle);
170 	if (ret) {
171 		dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));
172 		return ret;
173 	}
174 
175 	return devm_pwmchip_add(dev, &rpipwm->chip);
176 }
177 
178 static const struct of_device_id raspberrypi_pwm_of_match[] = {
179 	{ .compatible = "raspberrypi,firmware-poe-pwm", },
180 	{ }
181 };
182 MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
183 
184 static struct platform_driver raspberrypi_pwm_driver = {
185 	.driver = {
186 		.name = "raspberrypi-poe-pwm",
187 		.of_match_table = raspberrypi_pwm_of_match,
188 	},
189 	.probe = raspberrypi_pwm_probe,
190 };
191 module_platform_driver(raspberrypi_pwm_driver);
192 
193 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
194 MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
195 MODULE_LICENSE("GPL v2");
196