| /* |
| * This file is part of the coreboot project. |
| * |
| * Copyright 2014 Google Inc. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; version 2 of the License. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| #include <base3.h> |
| #include <console/console.h> |
| #include <delay.h> |
| #include <gpio.h> |
| |
| int gpio_base3_value(gpio_t gpio[], int num_gpio) |
| { |
| /* |
| * GPIOs which are tied to stronger external pull up or pull down |
| * will stay there regardless of the internal pull up or pull |
| * down setting. |
| * |
| * GPIOs which are floating will go to whatever level they're |
| * internally pulled to. |
| */ |
| |
| static const char tristate_char[] = {[0] = '0', [1] = '1', [Z] = 'Z'}; |
| int temp; |
| int index; |
| int result = 0; |
| char value[num_gpio]; |
| |
| /* Enable internal pull up */ |
| for (index = 0; index < num_gpio; ++index) |
| gpio_input_pullup(gpio[index]); |
| |
| /* Wait until signals become stable */ |
| udelay(10); |
| |
| /* Get gpio values at internal pull up */ |
| for (index = 0; index < num_gpio; ++index) |
| value[index] = gpio_get(gpio[index]); |
| |
| /* Enable internal pull down */ |
| for (index = 0; index < num_gpio; ++index) |
| gpio_input_pulldown(gpio[index]); |
| |
| /* Wait until signals become stable */ |
| udelay(10); |
| |
| /* |
| * Get gpio values at internal pull down. |
| * Compare with gpio pull up value and then |
| * determine a gpio final value/state: |
| * 0: pull down |
| * 1: pull up |
| * 2: floating |
| */ |
| printk(BIOS_DEBUG, "Reading tristate GPIOs: "); |
| for (index = num_gpio - 1; index >= 0; --index) { |
| temp = gpio_get(gpio[index]); |
| temp |= ((value[index] ^ temp) << 1); |
| printk(BIOS_DEBUG, "%c ", tristate_char[temp]); |
| result = (result * 3) + temp; |
| } |
| printk(BIOS_DEBUG, "= %d\n", result); |
| |
| /* Disable pull up / pull down to conserve power */ |
| for (index = 0; index < num_gpio; ++index) |
| gpio_input(gpio[index]); |
| |
| return result; |
| } |