diff options
Diffstat (limited to 'src/lib/gpio.c')
-rw-r--r-- | src/lib/gpio.c | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/src/lib/gpio.c b/src/lib/gpio.c new file mode 100644 index 0000000000..3a646e0d1d --- /dev/null +++ b/src/lib/gpio.c @@ -0,0 +1,82 @@ +/* + * 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; +} |