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Diffstat (limited to 'src/mainboard/google/gru/boardid.c')
| -rw-r--r-- | src/mainboard/google/gru/boardid.c | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/src/mainboard/google/gru/boardid.c b/src/mainboard/google/gru/boardid.c index f62fe97226..5f030adf01 100644 --- a/src/mainboard/google/gru/boardid.c +++ b/src/mainboard/google/gru/boardid.c @@ -16,9 +16,46 @@ #include <boardid.h> #include <console/console.h> #include <stdlib.h> +#include <soc/saradc.h> + +/* + * This matches two Kevin prototypes, needs to be sorted out with HW engs to + * have more regular mapping between the voltage and board ID. + */ +static const int board_id_readings[] = { 42, 120 }; + +/* + * 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; } |