drivers/w1/masters/w1-gpio.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * w1-gpio - GPIO w1 bus master driver
   4  *
   5  * Copyright (C) 2007 Ville Syrjala <syrjala@sci.fi>
   6  */
   7
   8 #include <linux/delay.h>
   9 #include <linux/device.h>
  10 #include <linux/err.h>
  11 #include <linux/gpio/consumer.h>
  12 #include <linux/mod_devicetable.h>
  13 #include <linux/module.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/property.h>
  16 #include <linux/types.h>
  17
  18 #include <linux/w1.h>
  19
  20 struct w1_gpio_ddata {
  21         struct gpio_desc *gpiod;
  22         struct gpio_desc *pullup_gpiod;
  23         unsigned int pullup_duration;
  24 };
  25
  26 static u8 w1_gpio_set_pullup(void *data, int delay)
  27 {
  28         struct w1_gpio_ddata *ddata = data;
  29
  30         if (delay) {
  31                 ddata->pullup_duration = delay;
  32         } else {
  33                 if (ddata->pullup_duration) {
  34                         /*
  35                          * This will OVERRIDE open drain emulation and force-pull
  36                          * the line high for some time.
  37                          */
  38                         gpiod_set_raw_value(ddata->gpiod, 1);
  39                         msleep(ddata->pullup_duration);
  40                         /*
  41                          * This will simply set the line as input since we are doing
  42                          * open drain emulation in the GPIO library.
  43                          */
  44                         gpiod_set_value(ddata->gpiod, 1);
  45                 }
  46                 ddata->pullup_duration = 0;
  47         }
  48
  49         return 0;
  50 }
  51
  52 static void w1_gpio_write_bit(void *data, u8 bit)
  53 {
  54         struct w1_gpio_ddata *ddata = data;
  55
  56         gpiod_set_value(ddata->gpiod, bit);
  57 }
  58
  59 static u8 w1_gpio_read_bit(void *data)
  60 {
  61         struct w1_gpio_ddata *ddata = data;
  62
  63         return gpiod_get_value(ddata->gpiod) ? 1 : 0;
  64 }
  65
  66 static int w1_gpio_probe(struct platform_device *pdev)
  67 {
  68         struct w1_bus_master *master;
  69         struct w1_gpio_ddata *ddata;
  70         struct device *dev = &pdev->dev;
  71         /* Enforce open drain mode by default */
  72         enum gpiod_flags gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
  73         int err;
  74
  75         ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
  76         if (!ddata)
  77                 return -ENOMEM;
  78
  79         /*
  80          * This parameter means that something else than the gpiolib has
  81          * already set the line into open drain mode, so we should just
  82          * driver it high/low like we are in full control of the line and
  83          * open drain will happen transparently.
  84          */
  85         if (device_property_present(dev, "linux,open-drain"))
  86                 gflags = GPIOD_OUT_LOW;
  87
  88         master = devm_kzalloc(dev, sizeof(*master), GFP_KERNEL);
  89         if (!master)
  90                 return -ENOMEM;
  91
  92         ddata->gpiod = devm_gpiod_get_index(dev, NULL, 0, gflags);
  93         if (IS_ERR(ddata->gpiod))
  94                 return dev_err_probe(dev, PTR_ERR(ddata->gpiod), "gpio_request (pin) failed\n");
  95
  96         ddata->pullup_gpiod =
  97                 devm_gpiod_get_index_optional(dev, NULL, 1, GPIOD_OUT_LOW);
  98         if (IS_ERR(ddata->pullup_gpiod))
  99                 return dev_err_probe(dev, PTR_ERR(ddata->pullup_gpiod),
 100                                      "gpio_request (ext_pullup_enable_pin) failed\n");
 101
 102         master->data = ddata;
 103         master->read_bit = w1_gpio_read_bit;
 104         gpiod_direction_output(ddata->gpiod, 1);
 105         master->write_bit = w1_gpio_write_bit;
 106
 107         /*
 108          * If we are using open drain emulation from the GPIO library,
 109          * we need to use this pullup function that hammers the line
 110          * high using a raw accessor to provide pull-up for the w1
 111          * line.
 112          */
 113         if (gflags == GPIOD_OUT_LOW_OPEN_DRAIN)
 114                 master->set_pullup = w1_gpio_set_pullup;
 115
 116         err = w1_add_master_device(master);
 117         if (err)
 118                 return dev_err_probe(dev, err, "w1_add_master device failed\n");
 119
 120         gpiod_set_value(ddata->pullup_gpiod, 1);
 121
 122         platform_set_drvdata(pdev, master);
 123
 124         return 0;
 125 }
 126
 127 static void w1_gpio_remove(struct platform_device *pdev)
 128 {
 129         struct w1_bus_master *master = platform_get_drvdata(pdev);
 130         struct w1_gpio_ddata *ddata = master->data;
 131
 132         gpiod_set_value(ddata->pullup_gpiod, 0);
 133
 134         w1_remove_master_device(master);
 135 }
 136
 137 static const struct of_device_id w1_gpio_dt_ids[] = {
 138         { .compatible = "w1-gpio" },
 139         {}
 140 };
 141 MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
 142
 143 static struct platform_driver w1_gpio_driver = {
 144         .driver = {
 145                 .name   = "w1-gpio",
 146                 .of_match_table = w1_gpio_dt_ids,
 147         },
 148         .probe = w1_gpio_probe,
 149         .remove_new = w1_gpio_remove,
 150 };
 151
 152 module_platform_driver(w1_gpio_driver);
 153
 154 MODULE_DESCRIPTION("GPIO w1 bus master driver");
 155 MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
 156 MODULE_LICENSE("GPL");