/* * 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. */ #include <assert.h> #include <base3.h> #include <console/console.h> #include <delay.h> #include <gpio.h> int gpio_base2_value(gpio_t gpio[], int num_gpio) { int i, result = 0; for (i = 0; i < num_gpio; i++) gpio_input(gpio[i]); /* Wait until signals become stable */ udelay(10); for (i = 0; i < num_gpio; i++) result |= gpio_get(gpio[i]) << i; return result; } int _gpio_base3_value(gpio_t gpio[], int num_gpio, int binary_first) { /* * 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; int has_z = 0; int binary_below = 0; char value[32]; assert(num_gpio <= 32); /* 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; /* * For binary_first we keep track of the normal ternary result * and whether we found any pin that was a Z. We also determine * the amount of numbers that can be represented with only * binary digits (no Z) whose value in the normal ternary system * is lower than the one we are parsing. Counting from the left, * we add 2^i for any '1' digit to account for the binary * numbers whose values would be below it if all following * digits we parsed would be '0'. As soon as we find a '2' digit * we can total the remaining binary numbers below as 2^(i+1) * because we know that all binary representations counting only * this and following digits must have values below our number * (since 1xxx is always smaller than 2xxx). * * Example: 1 0 2 1 (counting from the left / most significant) * '1' at 3^3: Add 2^3 = 8 to account for binaries 0000-0111 * '0' at 3^2: Ignore (not all binaries 1000-1100 are below us) * '2' at 3^1: Add 2^(1+1) = 4 to account for binaries 1000-1011 * Stop adding for lower digits (3^0), all already accounted * now. We know that there can be no binary numbers 1020-102X. */ if (binary_first && !has_z) { switch(temp) { case 0: /* Ignore '0' digits. */ break; case 1: /* Account for binaries 0 to 2^index - 1. */ binary_below += 1 << index; break; case 2: /* Account for binaries 0 to 2^(index+1) - 1. */ binary_below += 1 << (index + 1); has_z = 1; } } } if (binary_first) { if (has_z) result = result + (1 << num_gpio) - binary_below; else /* binary_below is normal binary system value if !has_z. */ result = binary_below; } printk(BIOS_DEBUG, "= %d (%s base3 number system)\n", result, binary_first ? "binary_first" : "standard"); /* Disable pull up / pull down to conserve power */ for (index = 0; index < num_gpio; ++index) gpio_input(gpio[index]); return result; }