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/*
* This file is part of the coreboot project.
*
* Copyright 2016 Rockchip 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 <boardid.h>
#include <console/console.h>
#include <stdlib.h>
#include <soc/saradc.h>
/*
* This matches Kevin/Gru ADC value for board id.
*/
static const int board_id_readings[] = { 42, 120, 181, 242, 307, 378, 444,
511, 581, 646, 704, 763, 828,
895, 956, 1023 };
/*
* The ADC produces a 10 bit value, the resistor accuracy is 1%, let's leave
* 2% room for error on both sides, total variation would be 4%, which is
* approximately 40 points with a 10 bit ADC. The hardware specification
* guarantees valid readings to be at least 64 bits (2^6) apart.
*/
#define ACCEPTABLE_DELTA (int)(1024 * .02)
uint8_t board_id(void)
{
static int cached_board_id = -1;
int i;
int adc_reading;
if (cached_board_id != -1)
return cached_board_id;
adc_reading = get_saradc_value(1);
for (i = 0; i < ARRAY_SIZE(board_id_readings); i++) {
int delta = board_id_readings[i] - adc_reading;
if ((delta < ACCEPTABLE_DELTA) && (delta > -ACCEPTABLE_DELTA)) {
printk(BIOS_DEBUG, "ADC reading %d, "
"expected value %d board ID %d\n",
adc_reading, delta + adc_reading, i);
cached_board_id = i;
return i;
}
}
printk(BIOS_ERR, "Unmatched ADC reading of %d, using Board ID of 0\n",
adc_reading);
return 0;
}
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