mb/google/geralt: Implement SKU ID and RAM code

- Retrieve the SKU ID for Geralt via CBI interface. If that failed
  (or no data found), fall back to ADC channels for SKU ID.
- The RAM code is implemented by the resistor straps that we can read
  and decode from ADC.

TEST=build pass
BUG=b:236331724

Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
Change-Id: I31626e44bd873a3866c9bd1d511b476737f15a20
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66275
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/geralt/Kconfig

@@ -23,6 +23,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select COMMONLIB_STORAGE_MMC
 	select EC_GOOGLE_CHROMEEC
 	select EC_GOOGLE_CHROMEEC_BOARDID
+	select EC_GOOGLE_CHROMEEC_SKUID
 	select EC_GOOGLE_CHROMEEC_SPI
 	select I2C_TPM if VBOOT
 	select MAINBOARD_HAS_TPM2 if VBOOT

src/mainboard/google/geralt/Makefile.inc

@@ -11,6 +11,7 @@ romstage-y += chromeos.c
 romstage-y += romstage.c
 
 ramstage-y += memlayout.ld
+ramstage-y += boardid.c
 ramstage-y += chromeos.c
 ramstage-y += mainboard.c
 ramstage-y += regulator.c

src/mainboard/google/geralt/boardid.c

@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <assert.h>
+#include <boardid.h>
+#include <console/console.h>
+#include <ec/google/chromeec/ec.h>
+#include <soc/auxadc.h>
+
+/* board_id is provided by ec/google/chromeec/ec_boardid.c */
+
+#define ADC_LEVELS 12
+
+enum {
+	/* RAM IDs */
+	RAM_ID_LOW_CHANNEL = 2,
+	RAM_ID_HIGH_CHANNEL = 3,
+	/* SKU IDs */
+	SKU_ID_LOW_CHANNEL = 4,
+	SKU_ID_HIGH_CHANNEL = 5,
+};
+
+static const unsigned int ram_voltages[ADC_LEVELS] = {
+	/* ID : Voltage (unit: uV) */
+	[0]  =   74300,
+	[1]  =  211700,
+	[2]  =  318800,
+	[3]  =  428600,
+	[4]  =  541700,
+	[5]  =  665800,
+	[6]  =  781400,
+	[7]  =  900000,
+	[8]  = 1023100,
+	[9]  = 1137000,
+	[10] = 1240000,
+	[11] = 1342600,
+};
+
+static const unsigned int *adc_voltages[] = {
+	[RAM_ID_LOW_CHANNEL] = ram_voltages,
+	[RAM_ID_HIGH_CHANNEL] = ram_voltages,
+	[SKU_ID_LOW_CHANNEL] = ram_voltages,
+	[SKU_ID_HIGH_CHANNEL] = ram_voltages,
+};
+
+static uint32_t get_adc_index(unsigned int channel)
+{
+	unsigned int value = auxadc_get_voltage_uv(channel);
+
+	assert(channel < ARRAY_SIZE(adc_voltages));
+	const unsigned int *voltages = adc_voltages[channel];
+	assert(voltages);
+
+	/* Find the closest voltage */
+	uint32_t id;
+	for (id = 0; id < ADC_LEVELS - 1; id++)
+		if (value < (voltages[id] + voltages[id + 1]) / 2)
+			break;
+
+	printk(BIOS_DEBUG, "ADC[%u]: Raw value=%u ID=%u\n", channel, value, id);
+	return id;
+}
+
+uint32_t sku_id(void)
+{
+	static uint32_t cached_sku_code = BOARD_ID_INIT;
+
+	if (cached_sku_code == BOARD_ID_INIT) {
+		cached_sku_code = google_chromeec_get_board_sku();
+
+		if (cached_sku_code == CROS_SKU_UNKNOWN) {
+			printk(BIOS_WARNING, "Failed to get SKU code from EC\n");
+			cached_sku_code = (get_adc_index(SKU_ID_HIGH_CHANNEL) << 4 |
+					   get_adc_index(SKU_ID_LOW_CHANNEL));
+		}
+		printk(BIOS_DEBUG, "SKU Code: %#02x\n", cached_sku_code);
+	}
+
+	return cached_sku_code;
+}
+
+uint32_t ram_code(void)
+{
+	static uint32_t cached_ram_code = BOARD_ID_INIT;
+
+	if (cached_ram_code == BOARD_ID_INIT) {
+		cached_ram_code = (get_adc_index(RAM_ID_HIGH_CHANNEL) << 4 |
+				   get_adc_index(RAM_ID_LOW_CHANNEL));
+		printk(BIOS_DEBUG, "RAM Code: %#02x\n", cached_ram_code);
+	}
+
+	return cached_ram_code;
+}