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 #include <linux/regmap.h>
  20
  21 #include <soc/bcm2835/raspberrypi-firmware.h>
  22 #include <dt-bindings/pwm/raspberrypi,firmware-poe-pwm.h>
  23
  24 #define RPI_PWM_MAX_DUTY                255
  25 #define RPI_PWM_PERIOD_NS               80000 /* 12.5 kHz */
  26
  27 #define RPI_PWM_CUR_DUTY_REG            0x0
  28
  29 struct raspberrypi_pwm {
  30         struct rpi_firmware *firmware;
  31
  32         struct regmap *regmap;
  33         u32 offset;
  34
  35         struct pwm_chip chip;
  36         unsigned int duty_cycle;
  37 };
  38
  39 struct raspberrypi_pwm_prop {
  40         __le32 reg;
  41         __le32 val;
  42         __le32 ret;
  43 } __packed;
  44
  45 static inline
  46 struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
  47 {
  48         return container_of(chip, struct raspberrypi_pwm, chip);
  49 }
  50
  51 static int raspberrypi_pwm_set_property(struct raspberrypi_pwm *pwm,
  52                                         u32 reg, u32 val)
  53 {
  54         struct raspberrypi_pwm_prop msg = {
  55                 .reg = cpu_to_le32(reg),
  56                 .val = cpu_to_le32(val),
  57         };
  58         int ret;
  59
  60         if (pwm->firmware) {
  61                 ret = rpi_firmware_property(pwm->firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
  62                                             &msg, sizeof(msg));
  63                 if (!ret && msg.ret)
  64                         ret = -EIO;
  65         } else {
  66                 ret = regmap_write(pwm->regmap, pwm->offset + reg, val);
  67         }
  68
  69         return ret;
  70 }
  71
  72 static int raspberrypi_pwm_get_property(struct raspberrypi_pwm *pwm,
  73                                         u32 reg, u32 *val)
  74 {
  75         struct raspberrypi_pwm_prop msg = {
  76                 .reg = cpu_to_le32(reg),
  77         };
  78         int ret;
  79
  80         if (pwm->firmware) {
  81                 ret = rpi_firmware_property(pwm->firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
  82                                             &msg, sizeof(msg));
  83                 if (!ret && msg.ret)
  84                         ret = -EIO;
  85                 *val = le32_to_cpu(msg.val);
  86         } else {
  87                 ret = regmap_read(pwm->regmap, pwm->offset + reg, val);
  88         }
  89
  90         return ret;
  91 }
  92
  93 static int raspberrypi_pwm_get_state(struct pwm_chip *chip,
  94                                      struct pwm_device *pwm,
  95                                      struct pwm_state *state)
  96 {
  97         struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
  98
  99         state->period = RPI_PWM_PERIOD_NS;
 100         state->duty_cycle = DIV_ROUND_UP(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
 101                                          RPI_PWM_MAX_DUTY);
 102         state->enabled = !!(rpipwm->duty_cycle);
 103         state->polarity = PWM_POLARITY_NORMAL;
 104
 105         return 0;
 106 }
 107
 108 static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 109                                  const struct pwm_state *state)
 110 {
 111         struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
 112         unsigned int duty_cycle;
 113         int ret;
 114
 115         if (state->period < RPI_PWM_PERIOD_NS ||
 116             state->polarity != PWM_POLARITY_NORMAL)
 117                 return -EINVAL;
 118
 119         if (!state->enabled)
 120                 duty_cycle = 0;
 121         else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
 122                 duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
 123                                                 RPI_PWM_PERIOD_NS);
 124         else
 125                 duty_cycle = RPI_PWM_MAX_DUTY;
 126
 127         if (duty_cycle == rpipwm->duty_cycle)
 128                 return 0;
 129
 130         ret = raspberrypi_pwm_set_property(rpipwm, RPI_PWM_CUR_DUTY_REG,
 131                                            duty_cycle);
 132         if (ret) {
 133                 dev_err(chip->dev, "Failed to set duty cycle: %pe\n",
 134                         ERR_PTR(ret));
 135                 return ret;
 136         }
 137
 138         rpipwm->duty_cycle = duty_cycle;
 139
 140         return 0;
 141 }
 142
 143 static const struct pwm_ops raspberrypi_pwm_ops = {
 144         .get_state = raspberrypi_pwm_get_state,
 145         .apply = raspberrypi_pwm_apply,
 146         .owner = THIS_MODULE,
 147 };
 148
 149 static int raspberrypi_pwm_probe(struct platform_device *pdev)
 150 {
 151         struct device_node *firmware_node;
 152         struct device *dev = &pdev->dev;
 153         struct rpi_firmware *firmware;
 154         struct raspberrypi_pwm *rpipwm;
 155         int ret;
 156
 157         rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);
 158         if (!rpipwm)
 159                 return -ENOMEM;
 160
 161         if (pdev->dev.parent)
 162                 rpipwm->regmap = dev_get_regmap(pdev->dev.parent, NULL);
 163
 164         if (rpipwm->regmap) {
 165                 ret = device_property_read_u32(&pdev->dev, "reg", &rpipwm->offset);
 166                 if (ret)
 167                         return -EINVAL;
 168         } else {
 169                 firmware_node = of_get_parent(dev->of_node);
 170
 171                 firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
 172                 of_node_put(firmware_node);
 173                 if (!firmware)
 174                         return dev_err_probe(dev, -EPROBE_DEFER,
 175                                              "Failed to get firmware handle\n");
 176
 177                 rpipwm->firmware = firmware;
 178         }
 179
 180         rpipwm->chip.dev = dev;
 181         rpipwm->chip.ops = &raspberrypi_pwm_ops;
 182         rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
 183
 184         ret = raspberrypi_pwm_get_property(rpipwm, RPI_PWM_CUR_DUTY_REG,
 185                                            &rpipwm->duty_cycle);
 186         if (ret) {
 187                 dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));
 188                 return ret;
 189         }
 190
 191         return devm_pwmchip_add(dev, &rpipwm->chip);
 192 }
 193
 194 static const struct of_device_id raspberrypi_pwm_of_match[] = {
 195         { .compatible = "raspberrypi,firmware-poe-pwm", },
 196         { .compatible = "raspberrypi,poe-pwm", },
 197         { }
 198 };
 199 MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
 200
 201 static struct platform_driver raspberrypi_pwm_driver = {
 202         .driver = {
 203                 .name = "raspberrypi-poe-pwm",
 204                 .of_match_table = raspberrypi_pwm_of_match,
 205         },
 206         .probe = raspberrypi_pwm_probe,
 207 };
 208 module_platform_driver(raspberrypi_pwm_driver);
 209
 210 MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@suse.de>");
 211 MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
 212 MODULE_LICENSE("GPL v2");