google/kukui: Include LCD module identifier (LCM ID) into SKU ID

Kukui is using MIPI display panel and needs some identifier to tell
payloads which LCD module is installed, and to select right kernel
device tree. Following Scarlet, the decision is to embed LCD module ID
as part of SKU ID.

The LCM ID is using a different voltage mapping table from the rest.
Considering the complexity in computation of SKU ID, it is better to
move the cache logic from get_index to caller.

Also revise the mapping table since ADC on 8183 only supports 12
levels.

BUG=b:129299873
TEST=make -j; boots on Kukui Rev2 unit.

Change-Id: Ib0c00bc8ce3c71c445c5c4561403ce8ef4dd5844
Signed-off-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32263
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/kukui/boardid.c

@@ -22,9 +22,15 @@
 /* For CBI un-provisioned/corrupted Flapjack board. */
 #define FLAPJACK_UNDEF_SKU_ID 0
 
-static uint32_t get_index(unsigned int channel, uint32_t *cached_id)
+#define ADC_LEVELS 12
-{
+
-	static const int voltages[] = {
+enum {
+	LCM_ID_CHANNEL = 2,  /* ID of LCD Module on schematics. */
+	RAM_ID_CHANNEL = 3,
+	SKU_ID_CHANNEL = 4,
+};
+
+static const int ram_voltages[ADC_LEVELS] = {
 	/* ID : Voltage (unit: uV) */
 	/*  0 : */   74000,
 	/*  1 : */  212000,
@@ -38,27 +44,47 @@ static uint32_t get_index(unsigned int channel, uint32_t *cached_id)
 	/*  9 : */ 1137000,
 	/* 10 : */ 1240000,
 	/* 11 : */ 1343000,
-	/* 12 : */ 1457000,
+};
-	/* 13 : */ 1576000,
-	/* 14 : */ 1684000,
-	/* 15 : */ 1800000,
-	};
 
-	uint32_t id;
+static const int lcm_voltages[ADC_LEVELS] = {
+	/* ID : Voltage (unit: uV) */
+	/*  0 : */       0,
+	/*  1 : */  283000,
+	/*  2 : */  440000,
+	/*  3 : */  503000,
+	/*  4 : */  608000,
+	/*  5 : */  703000,
+	/*  6 : */  830000,
+	/*  7 : */  865000,
+	/*  8 : */  953000,
+	/*  9 : */ 1079000,
+	/* 10 : */ 1128000,
+	/* 11 : */ 1434000,
+};
 
-	if (*cached_id != BOARD_ID_INIT)
+static const int *adc_voltages[] = {
-		return *cached_id;
+	[LCM_ID_CHANNEL] = lcm_voltages,
+	[RAM_ID_CHANNEL] = ram_voltages,
+	[SKU_ID_CHANNEL] = ram_voltages, /* SKU ID is sharing RAM voltages. */
+};
 
+static uint32_t get_adc_index(unsigned int channel)
+{
 	int value = auxadc_get_voltage(channel);
+
+	assert(channel < ARRAY_SIZE(adc_voltages));
+	const int *voltages = adc_voltages[channel];
+	assert(voltages);
+
 	/* Find the closest voltage */
-	for (id = 0; id < ARRAY_SIZE(voltages) - 1; id++)
+	uint32_t id;
+	for (id = 0; id < ADC_LEVELS - 1; id++)
 		if (value < (voltages[id] + voltages[id + 1]) / 2)
 			break;
 
 	const int tolerance = 10000; /* 10,000 uV */
 	assert(ABS(value - voltages[id]) < tolerance);
 
-	*cached_id = id;
 	return id;
 }
 
@@ -68,26 +94,39 @@ uint32_t sku_id(void)
 {
 	static uint32_t cached_sku_id = BOARD_ID_INIT;
 
+	if (cached_sku_id != BOARD_ID_INIT)
+		return cached_sku_id;
+
 	/* On Flapjack, getting the SKU via CBI. */
 	if (CONFIG(BOARD_GOOGLE_FLAPJACK)) {
-		if (cached_sku_id == BOARD_ID_INIT &&
+		if (google_chromeec_cbi_get_sku_id(&cached_sku_id))
-		    google_chromeec_cbi_get_sku_id(&cached_sku_id))
 			cached_sku_id = FLAPJACK_UNDEF_SKU_ID;
 		return cached_sku_id;
 	}
 
-	/* Quirk for KUKUI: All P1/SKU0 had incorrectly set SKU=1. */
+	/* Quirk for Kukui: All Rev1/Sku0 had incorrectly set SKU_ID=1. */
 	if (CONFIG(BOARD_GOOGLE_KUKUI)) {
-		if (cached_sku_id == BOARD_ID_INIT && board_id() == 1) {
+		if (board_id() == 1) {
 			cached_sku_id = 0;
 			return cached_sku_id;
 		}
 	}
-	return get_index(4, &cached_sku_id);
+
+	/*
+	 * The SKU (later used for device tree matching) is combined from:
+	 * ADC2[4bit/H] = straps on LCD module (type of panel).
+	 * ADC4[4bit/L] = SKU ID from board straps.
+	 */
+	cached_sku_id = (get_adc_index(LCM_ID_CHANNEL) << 4 |
+			 get_adc_index(SKU_ID_CHANNEL));
+	return cached_sku_id;
 }
 
 uint32_t ram_code(void)
 {
 	static uint32_t cached_ram_code = BOARD_ID_INIT;
-	return get_index(3, &cached_ram_code);
+
+	if (cached_ram_code == BOARD_ID_INIT)
+		cached_ram_code = get_adc_index(RAM_ID_CHANNEL);
+	return cached_ram_code;
 }