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 = cpu_to_le32(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"); 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