drivers/pwm/pwm-raspberrypi-poe.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2021 Nicolas Saenz Julienne <[email protected]>
   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         unsigned int duty_cycle;
  31 };
  32
  33 struct raspberrypi_pwm_prop {
  34         __le32 reg;
  35         __le32 val;
  36         __le32 ret;
  37 } __packed;
  38
  39 static inline
  40 struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
  41 {
  42         return pwmchip_get_drvdata(chip);
  43 }
  44
  45 static 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
  64 static 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
  84 static 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
  99 static 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
 134 static const struct pwm_ops raspberrypi_pwm_ops = {
 135         .get_state = raspberrypi_pwm_get_state,
 136         .apply = raspberrypi_pwm_apply,
 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 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
 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 <[email protected]>");
 195 MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
 196 MODULE_LICENSE("GPL v2");