src/lib/gpio.c

   1 /*
   2  * This file is part of the coreboot project.
   3  *
   4  * Copyright 2014 Google Inc.
   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 as published by
   8  * the Free Software Foundation; version 2 of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <assert.h>
  17 #include <base3.h>
  18 #include <console/console.h>
  19 #include <delay.h>
  20 #include <gpio.h>
  21
  22 int gpio_base2_value(gpio_t gpio[], int num_gpio)
  23 {
  24         int i, result = 0;
  25
  26         for (i = 0; i < num_gpio; i++)
  27                 gpio_input(gpio[i]);
  28
  29         /* Wait until signals become stable */
  30         udelay(10);
  31
  32         for (i = 0; i < num_gpio; i++)
  33                 result |= gpio_get(gpio[i]) << i;
  34
  35         return result;
  36 }
  37
  38 int gpio_base3_value(gpio_t gpio[], int num_gpio)
  39 {
  40         /*
  41          * GPIOs which are tied to stronger external pull up or pull down
  42          * will stay there regardless of the internal pull up or pull
  43          * down setting.
  44          *
  45          * GPIOs which are floating will go to whatever level they're
  46          * internally pulled to.
  47          */
  48
  49         static const char tristate_char[] = {[0] = '0', [1] = '1', [Z] = 'Z'};
  50         int temp;
  51         int index;
  52         int result = 0;
  53         char value[32];
  54         assert(num_gpio <= 32);
  55
  56         /* Enable internal pull up */
  57         for (index = 0; index < num_gpio; ++index)
  58                 gpio_input_pullup(gpio[index]);
  59
  60         /* Wait until signals become stable */
  61         udelay(10);
  62
  63         /* Get gpio values at internal pull up */
  64         for (index = 0; index < num_gpio; ++index)
  65                 value[index] = gpio_get(gpio[index]);
  66
  67         /* Enable internal pull down */
  68         for (index = 0; index < num_gpio; ++index)
  69                 gpio_input_pulldown(gpio[index]);
  70
  71         /* Wait until signals become stable */
  72         udelay(10);
  73
  74         /*
  75          * Get gpio values at internal pull down.
  76          * Compare with gpio pull up value and then
  77          * determine a gpio final value/state:
  78          *  0: pull down
  79          *  1: pull up
  80          *  2: floating
  81          */
  82         printk(BIOS_DEBUG, "Reading tristate GPIOs: ");
  83         for (index = num_gpio - 1; index >= 0; --index) {
  84                 temp = gpio_get(gpio[index]);
  85                 temp |= ((value[index] ^ temp) << 1);
  86                 printk(BIOS_DEBUG, "%c ", tristate_char[temp]);
  87                 result = (result * 3) + temp;
  88         }
  89         printk(BIOS_DEBUG, "= %d\n", result);
  90
  91         /* Disable pull up / pull down to conserve power */
  92         for (index = 0; index < num_gpio; ++index)
  93                 gpio_input(gpio[index]);
  94
  95         return result;
  96 }