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/*
* 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 <delay.h>
#include <gpio.h>
int gpio_get_tristates(gpio_t gpio[], int num_gpio, int tertiary)
{
/*
* 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.
*/
int temp;
int index;
int id = 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
*/
for (index = num_gpio - 1; index >= 0; --index) {
if (tertiary)
id *= 3;
else
id <<= 2;
temp = gpio_get(gpio[index]);
id += ((value[index] ^ temp) << 1) | temp;
}
/* Disable pull up / pull down to conserve power */
for (index = 0; index < num_gpio; ++index)
gpio_input(gpio[index]);
return id;
}
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