gpio.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <base3.h>
#include <console/console.h>
#include <delay.h>
#include <gpio.h>
 
static void _check_num(const char *name, int num)
{
        if ((num > 31) || (num < 1)) {
                printk(BIOS_EMERG, "%s: %d ", name, num);
                die("is an invalid number of GPIOs");
        }
}
 
static uint32_t _gpio_base2_value(const gpio_t gpio[], int num_gpio)
{
        uint32_t result = 0;
        int i;
 
        /* Wait until signals become stable */
        udelay(10);
 
        for (i = 0; i < num_gpio; i++)
                result |= gpio_get(gpio[i]) << i;
 
        return result;
}
 
uint32_t gpio_base2_value(const gpio_t gpio[], int num_gpio)
{
        int i;
 
        _check_num(__func__, num_gpio);
        for (i = 0; i < num_gpio; i++)
                gpio_input(gpio[i]);
 
        return _gpio_base2_value(gpio, num_gpio);
}
 
uint32_t gpio_pulldown_base2_value(const gpio_t gpio[], int num_gpio)
{
        int i;
 
        _check_num(__func__, num_gpio);
        for (i = 0; i < num_gpio; i++)
                gpio_input_pulldown(gpio[i]);
 
        return _gpio_base2_value(gpio, num_gpio);
}
 
uint32_t gpio_pullup_base2_value(const gpio_t gpio[], int num_gpio)
{
        int i;
 
        _check_num(__func__, num_gpio);
        for (i = 0; i < num_gpio; i++)
                gpio_input_pullup(gpio[i]);
 
        return _gpio_base2_value(gpio, num_gpio);
}
 
uint32_t _gpio_base3_value(const 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'};
        uint32_t result = 0;
        int has_z = 0;
        int binary_below = 0;
        int index;
        int temp;
        char value[32];
 
        _check_num(__func__, 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;
 
                /* Disable pull to avoid wasting power. For HiZ we leave the
                   pull-down enabled, since letting them float freely back and
                   forth may waste power in the SoC's GPIO input logic. */
                if (temp != Z)
                        gpio_input(gpio[index]);
 
                /*
                 * 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");
 
        return result;
}
 
/* Default handler for ACPI path is to return NULL */
__weak const char *gpio_acpi_path(gpio_t gpio)
{
        return NULL;
}
 
/* Default handler returns 0 because type of gpio_t is unknown */
__weak uint16_t gpio_acpi_pin(gpio_t gpio)
{
        return 0;
}