drivers/w1/masters/w1-gpio.c

   1 /*
   2  * w1-gpio - GPIO w1 bus master driver
   3  *
   4  * Copyright (C) 2007 Ville Syrjala <syrjala@sci.fi>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2
   8  * as published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/init.h>
  12 #include <linux/module.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/slab.h>
  15 #include <linux/w1-gpio.h>
  16 #include <linux/gpio/consumer.h>
  17 #include <linux/of_platform.h>
  18 #include <linux/err.h>
  19 #include <linux/of.h>
  20 #include <linux/delay.h>
  21
  22 #include <linux/w1.h>
  23
  24 static u8 w1_gpio_set_pullup(void *data, int delay)
  25 {
  26         struct w1_gpio_platform_data *pdata = data;
  27
  28         if (delay) {
  29                 pdata->pullup_duration = delay;
  30         } else {
  31                 if (pdata->pullup_duration) {
  32                         /*
  33                          * This will OVERRIDE open drain emulation and force-pull
  34                          * the line high for some time.
  35                          */
  36                         gpiod_set_raw_value(pdata->gpiod, 1);
  37                         msleep(pdata->pullup_duration);
  38                         /*
  39                          * This will simply set the line as input since we are doing
  40                          * open drain emulation in the GPIO library.
  41                          */
  42                         gpiod_set_value(pdata->gpiod, 1);
  43                 }
  44                 pdata->pullup_duration = 0;
  45         }
  46
  47         return 0;
  48 }
  49
  50 static void w1_gpio_write_bit(void *data, u8 bit)
  51 {
  52         struct w1_gpio_platform_data *pdata = data;
  53
  54         gpiod_set_value(pdata->gpiod, bit);
  55 }
  56
  57 static u8 w1_gpio_read_bit(void *data)
  58 {
  59         struct w1_gpio_platform_data *pdata = data;
  60
  61         return gpiod_get_value(pdata->gpiod) ? 1 : 0;
  62 }
  63
  64 #if defined(CONFIG_OF)
  65 static const struct of_device_id w1_gpio_dt_ids[] = {
  66         { .compatible = "w1-gpio" },
  67         {}
  68 };
  69 MODULE_DEVICE_TABLE(of, w1_gpio_dt_ids);
  70 #endif
  71
  72 static int w1_gpio_probe(struct platform_device *pdev)
  73 {
  74         struct w1_bus_master *master;
  75         struct w1_gpio_platform_data *pdata;
  76         struct device *dev = &pdev->dev;
  77         struct device_node *np = dev->of_node;
  78         /* Enforce open drain mode by default */
  79         enum gpiod_flags gflags = GPIOD_OUT_LOW_OPEN_DRAIN;
  80         int err;
  81
  82         if (of_have_populated_dt()) {
  83                 pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
  84                 if (!pdata)
  85                         return -ENOMEM;
  86
  87                 /*
  88                  * This parameter means that something else than the gpiolib has
  89                  * already set the line into open drain mode, so we should just
  90                  * driver it high/low like we are in full control of the line and
  91                  * open drain will happen transparently.
  92                  */
  93                 if (of_get_property(np, "linux,open-drain", NULL))
  94                         gflags = GPIOD_OUT_LOW;
  95
  96                 pdev->dev.platform_data = pdata;
  97         }
  98         pdata = dev_get_platdata(dev);
  99
 100         if (!pdata) {
 101                 dev_err(dev, "No configuration data\n");
 102                 return -ENXIO;
 103         }
 104
 105         master = devm_kzalloc(dev, sizeof(struct w1_bus_master),
 106                         GFP_KERNEL);
 107         if (!master) {
 108                 dev_err(dev, "Out of memory\n");
 109                 return -ENOMEM;
 110         }
 111
 112         pdata->gpiod = devm_gpiod_get_index(dev, NULL, 0, gflags);
 113         if (IS_ERR(pdata->gpiod)) {
 114                 dev_err(dev, "gpio_request (pin) failed\n");
 115                 return PTR_ERR(pdata->gpiod);
 116         }
 117
 118         pdata->pullup_gpiod =
 119                 devm_gpiod_get_index_optional(dev, NULL, 1, GPIOD_OUT_LOW);
 120         if (IS_ERR(pdata->pullup_gpiod)) {
 121                 dev_err(dev, "gpio_request_one "
 122                         "(ext_pullup_enable_pin) failed\n");
 123                 return PTR_ERR(pdata->pullup_gpiod);
 124         }
 125
 126         master->data = pdata;
 127         master->read_bit = w1_gpio_read_bit;
 128         gpiod_direction_output(pdata->gpiod, 1);
 129         master->write_bit = w1_gpio_write_bit;
 130
 131         /*
 132          * If we are using open drain emulation from the GPIO library,
 133          * we need to use this pullup function that hammers the line
 134          * high using a raw accessor to provide pull-up for the w1
 135          * line.
 136          */
 137         if (gflags == GPIOD_OUT_LOW_OPEN_DRAIN)
 138                 master->set_pullup = w1_gpio_set_pullup;
 139
 140         err = w1_add_master_device(master);
 141         if (err) {
 142                 dev_err(dev, "w1_add_master device failed\n");
 143                 return err;
 144         }
 145
 146         if (pdata->enable_external_pullup)
 147                 pdata->enable_external_pullup(1);
 148
 149         if (pdata->pullup_gpiod)
 150                 gpiod_set_value(pdata->pullup_gpiod, 1);
 151
 152         platform_set_drvdata(pdev, master);
 153
 154         return 0;
 155 }
 156
 157 static int w1_gpio_remove(struct platform_device *pdev)
 158 {
 159         struct w1_bus_master *master = platform_get_drvdata(pdev);
 160         struct w1_gpio_platform_data *pdata = dev_get_platdata(&pdev->dev);
 161
 162         if (pdata->enable_external_pullup)
 163                 pdata->enable_external_pullup(0);
 164
 165         if (pdata->pullup_gpiod)
 166                 gpiod_set_value(pdata->pullup_gpiod, 0);
 167
 168         w1_remove_master_device(master);
 169
 170         return 0;
 171 }
 172
 173 static int __maybe_unused w1_gpio_suspend(struct device *dev)
 174 {
 175         struct w1_gpio_platform_data *pdata = dev_get_platdata(dev);
 176
 177         if (pdata->enable_external_pullup)
 178                 pdata->enable_external_pullup(0);
 179
 180         return 0;
 181 }
 182
 183 static int __maybe_unused w1_gpio_resume(struct device *dev)
 184 {
 185         struct w1_gpio_platform_data *pdata = dev_get_platdata(dev);
 186
 187         if (pdata->enable_external_pullup)
 188                 pdata->enable_external_pullup(1);
 189
 190         return 0;
 191 }
 192
 193 static SIMPLE_DEV_PM_OPS(w1_gpio_pm_ops, w1_gpio_suspend, w1_gpio_resume);
 194
 195 static struct platform_driver w1_gpio_driver = {
 196         .driver = {
 197                 .name   = "w1-gpio",
 198                 .pm     = &w1_gpio_pm_ops,
 199                 .of_match_table = of_match_ptr(w1_gpio_dt_ids),
 200         },
 201         .probe = w1_gpio_probe,
 202         .remove = w1_gpio_remove,
 203 };
 204
 205 module_platform_driver(w1_gpio_driver);
 206
 207 MODULE_DESCRIPTION("GPIO w1 bus master driver");
 208 MODULE_AUTHOR("Ville Syrjala <syrjala@sci.fi>");
 209 MODULE_LICENSE("GPL");