src/mainboard/google/storm/boardid.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <boardid.h>
   4 #include <gpio.h>
   5 #include <console/console.h>
   6
   7 /*
   8  * Storm boards dedicate to the board ID three GPIOs in tertiary mode: 29, 30
   9  * and 68. On proto0 GPIO68 is used and tied low, so it reads as 'zero' by
  10  * gpio_base3_value(), whereas the other two pins are not connected
  11  * and read as 'two'. This results in gpio_base3_value() returning
  12  * 8 on proto0.
  13  *
  14  * Three tertitiary signals could represent 27 different values. To make
  15  * calculated board ID value continuous and starting at zero, offset the
  16  * calculated value by 19 (i.e. 27 - 8) and return modulo 27 of the offset
  17  * number. This results in proto0 returning zero as the board ID, the future
  18  * revisions will have the inputs configured to match the actual board
  19  * revision.
  20  */
  21
  22 static int board_id_value = -1;
  23
  24 static uint8_t get_board_id(void)
  25 {
  26         uint8_t bid;
  27         gpio_t hw_rev_gpios[] = {[2] = 68, [1] = 30, [0] = 29}; /* 29 is LSB */
  28         int offset = 19;
  29
  30         bid = gpio_base3_value(hw_rev_gpios, ARRAY_SIZE(hw_rev_gpios));
  31         bid = (bid + offset) % 27;
  32         printk(BIOS_INFO, "Board ID %d\n", bid);
  33
  34         return bid;
  35 }
  36
  37 uint32_t board_id(void)
  38 {
  39         if (board_id_value < 0)
  40                 board_id_value = get_board_id();
  41
  42         return board_id_value;
  43 }