include/asm-generic/gpio.h

   1 /*
   2  * Copyright (c) 2011 The Chromium OS Authors.
   3  * Copyright (c) 2011, NVIDIA Corp. All rights reserved.
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  */
   6
   7 #ifndef _ASM_GENERIC_GPIO_H_
   8 #define _ASM_GENERIC_GPIO_H_
   9
  10 /*
  11  * Generic GPIO API for U-Boot
  12  *
  13  * GPIOs are numbered from 0 to GPIO_COUNT-1 which value is defined
  14  * by the SOC/architecture.
  15  *
  16  * Each GPIO can be an input or output. If an input then its value can
  17  * be read as 0 or 1. If an output then its value can be set to 0 or 1.
  18  * If you try to write an input then the value is undefined. If you try
  19  * to read an output, barring something very unusual,  you will get
  20  * back the value of the output that you previously set.
  21  *
  22  * In some cases the operation may fail, for example if the GPIO number
  23  * is out of range, or the GPIO is not available because its pin is
  24  * being used by another function. In that case, functions may return
  25  * an error value of -1.
  26  */
  27
  28 /**
  29  * Request a gpio. This should be called before any of the other functions
  30  * are used on this gpio.
  31  *
  32  * @param gp    GPIO number
  33  * @param label User label for this GPIO
  34  * @return 0 if ok, -1 on error
  35  */
  36 int gpio_request(unsigned gpio, const char *label);
  37
  38 /**
  39  * Stop using the GPIO.  This function should not alter pin configuration.
  40  *
  41  * @param gpio  GPIO number
  42  * @return 0 if ok, -1 on error
  43  */
  44 int gpio_free(unsigned gpio);
  45
  46 /**
  47  * Make a GPIO an input.
  48  *
  49  * @param gpio  GPIO number
  50  * @return 0 if ok, -1 on error
  51  */
  52 int gpio_direction_input(unsigned gpio);
  53
  54 /**
  55  * Make a GPIO an output, and set its value.
  56  *
  57  * @param gpio  GPIO number
  58  * @param value GPIO value (0 for low or 1 for high)
  59  * @return 0 if ok, -1 on error
  60  */
  61 int gpio_direction_output(unsigned gpio, int value);
  62
  63 /**
  64  * Get a GPIO's value. This will work whether the GPIO is an input
  65  * or an output.
  66  *
  67  * @param gpio  GPIO number
  68  * @return 0 if low, 1 if high, -1 on error
  69  */
  70 int gpio_get_value(unsigned gpio);
  71
  72 /**
  73  * Set an output GPIO's value. The GPIO must already be an output or
  74  * this function may have no effect.
  75  *
  76  * @param gpio  GPIO number
  77  * @param value GPIO value (0 for low or 1 for high)
  78  * @return 0 if ok, -1 on error
  79  */
  80 int gpio_set_value(unsigned gpio, int value);
  81
  82 /* State of a GPIO, as reported by get_state() */
  83 enum {
  84         GPIOF_INPUT = 0,
  85         GPIOF_OUTPUT,
  86         GPIOF_UNKNOWN,
  87 };
  88
  89 struct udevice;
  90
  91 /**
  92  * struct struct dm_gpio_ops - Driver model GPIO operations
  93  *
  94  * Refer to functions above for description. These function largely copy
  95  * the old API.
  96  *
  97  * This is trying to be close to Linux GPIO API. Once the U-Boot uses the
  98  * new DM GPIO API, this should be really easy to flip over to the Linux
  99  * GPIO API-alike interface.
 100  *
 101  * Akso it would be useful to standardise additional functions like
 102  * pullup, slew rate and drive strength.
 103  *
 104  * gpio_request)( and gpio_free() are optional - if NULL then they will
 105  * not be called.
 106  *
 107  * Note that @offset is the offset from the base GPIO of the device. So
 108  * offset 0 is the device's first GPIO and offset o-1 is the last GPIO,
 109  * where o is the number of GPIO lines controlled by the device. A device
 110  * is typically used to control a single bank of GPIOs. Within complex
 111  * SoCs there may be many banks and therefore many devices all referring
 112  * to the different IO addresses within the SoC.
 113  *
 114  * The uclass combines all GPIO devices togther to provide a consistent
 115  * numbering from 0 to n-1, where n is the number of GPIOs in total across
 116  * all devices. Be careful not to confuse offset with gpio in the parameters.
 117  */
 118 struct dm_gpio_ops {
 119         int (*request)(struct udevice *dev, unsigned offset, const char *label);
 120         int (*free)(struct udevice *dev, unsigned offset);
 121         int (*direction_input)(struct udevice *dev, unsigned offset);
 122         int (*direction_output)(struct udevice *dev, unsigned offset,
 123                                 int value);
 124         int (*get_value)(struct udevice *dev, unsigned offset);
 125         int (*set_value)(struct udevice *dev, unsigned offset, int value);
 126         int (*get_function)(struct udevice *dev, unsigned offset);
 127         int (*get_state)(struct udevice *dev, unsigned offset, char *state,
 128                          int maxlen);
 129 };
 130
 131 /**
 132  * struct gpio_dev_priv - information about a device used by the uclass
 133  *
 134  * The uclass combines all active GPIO devices into a unified numbering
 135  * scheme. To do this it maintains some private information aobut each
 136  * device.
 137  *
 138  * To implement driver model support in your GPIO driver, add a probe
 139  * handler, and set @gpio_count and @bank_name correctly in that handler.
 140  * This tells the uclass the name of the GPIO bank and the number of GPIOs
 141  * it contains.
 142  *
 143  * @bank_name: Name of the GPIO device (e.g 'a' means GPIOs will be called
 144  * 'A0', 'A1', etc.
 145  * @gpio_count: Number of GPIOs in this device
 146  * @gpio_base: Base GPIO number for this device. For the first active device
 147  * this will be 0; the numbering for others will follow sequentially so that
 148  * @gpio_base for device 1 will equal the number of GPIOs in device 0.
 149  */
 150 struct gpio_dev_priv {
 151         const char *bank_name;
 152         unsigned gpio_count;
 153         unsigned gpio_base;
 154 };
 155
 156 /* Access the GPIO operations for a device */
 157 #define gpio_get_ops(dev)       ((struct dm_gpio_ops *)(dev)->driver->ops)
 158
 159 /**
 160  * gpio_get_bank_info - Return information about a GPIO bank/device
 161  *
 162  * This looks up a device and returns both its GPIO base name and the number
 163  * of GPIOs it controls.
 164  *
 165  * @dev: Device to look up
 166  * @offset_count: Returns number of GPIOs within this bank
 167  * @return bank name of this device
 168  */
 169 const char *gpio_get_bank_info(struct udevice *dev, int *offset_count);
 170
 171 /**
 172  * gpio_lookup_name - Look up a GPIO name and return its details
 173  *
 174  * This is used to convert a named GPIO into a device, offset and GPIO
 175  * number.
 176  *
 177  * @name: GPIO name to look up
 178  * @devp: Returns pointer to device which contains this GPIO
 179  * @offsetp: Returns the offset number within this device
 180  * @gpiop: Returns the absolute GPIO number, numbered from 0
 181  */
 182 int gpio_lookup_name(const char *name, struct udevice **devp,
 183                      unsigned int *offsetp, unsigned int *gpiop);
 184
 185 #endif  /* _ASM_GENERIC_GPIO_H_ */