drivers/pwm/pwm-raspberrypi-poe.c

   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");