mb/google/skywalker: Add support for getting storage id

Add storage_id() to read the storage id from AUXADC.

BUG=b:379008996
BRANCH=none
TEST=check log on Skywalker SKU1
[DEBUG]  ADC[2]: Raw value=73782 ID=0

Signed-off-by: Vince Liu <vince-wl.liu@mediatek.corp-partner.google.com>
Change-Id: I83cb52df1f25c5106fbe213e8a0185ae764fd7dc
Reviewed-on: https://review.coreboot.org/c/coreboot/+/87921
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-by: Yidi Lin <yidilin@google.com>

src/mainboard/google/skywalker/boardid.c

@@ -1,8 +1,66 @@
 /* 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_common.h>
+
+#include "storage.h"
+
+#define ADC_LEVELS 8
+
+enum {
+	/* STORAGE IDs */
+	STORAGE_ID_CHANNEL = 2,
+};
+
+static const unsigned int storage_voltages[ADC_LEVELS] = {
+	/* ID : Voltage (unit: uV) */
+	[0] =   74300,
+	[1] =  211400,
+	[2] =  365100,
+	[3] =  524300,
+	[4] =  706300,
+	[5] =  899100,
+	[6] = 1108900,
+	[7] = 1342600,
+};
+
+static const unsigned int *adc_voltages[] = {
+	[STORAGE_ID_CHANNEL] = storage_voltages,
+};
+
+static uint32_t get_adc_index(unsigned int channel)
+{
+	unsigned int value = auxadc_get_voltage_uv(channel);
+	const unsigned int *voltages;
+
+	assert(channel < ARRAY_SIZE(adc_voltages));
+	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 storage_id(void)
+{
+	static uint32_t cached_storage_id = BOARD_ID_INIT;
+
+	if (cached_storage_id == BOARD_ID_INIT)
+		cached_storage_id = get_adc_index(STORAGE_ID_CHANNEL);
+
+	printk(BIOS_DEBUG, "Storage ID: %#02x\n", cached_storage_id);
+	return cached_storage_id;
+}
 
 uint32_t sku_id(void)
 {

src/mainboard/google/skywalker/mainboard.c

@@ -11,9 +11,11 @@
 #include <soc/mt6359p.h>
 #include <soc/mtcmos.h>
 #include <soc/spm_common.h>
+#include <soc/storage.h>
 #include <soc/usb.h>
 
 #include "gpio.h"
+#include "storage.h"
 
 #define AFE_SE_SECURE_CON1	(AUDIO_BASE + 0x5634)
 
@@ -65,6 +67,23 @@ static void power_on_fpmcu(void)
 	gpio_output(GPIO_FP_RST_1V8_S3_L, 1);
 }
 
+enum mtk_storage_type mainboard_get_storage_type(void)
+{
+	uint32_t index = storage_id();
+
+	switch (index) {
+	case 0:
+		return STORAGE_UFS_31;
+	case 1:
+		return STORAGE_UFS_22;
+	case 2:
+		return STORAGE_EMMC;
+	default:
+		printk(BIOS_WARNING, "unsupported storage id %u\n", index);
+	}
+	return STORAGE_UNKNOWN;
+}
+
 static void mainboard_init(struct device *dev)
 {
 	dpm_init();

src/mainboard/google/skywalker/storage.h

@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
+
+#ifndef __MAINBOARD_GOOGLE_SKYWALKER_STORAGE_H__
+#define __MAINBOARD_GOOGLE_SKYWALKER_STORAGE_H__
+
+uint32_t storage_id(void);
+
+#endif