--- /dev/null
+++ board/friendlyarm/nanopi4/hwrev.c	2021-04-17 08:23:24.947758000 +0300
@@ -0,0 +1,185 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2020 FriendlyElec Computer Tech. Co., Ltd.
+ * (http://www.friendlyarm.com)
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <linux/delay.h>
+#include <log.h>
+#include <asm/io.h>
+#include <asm/gpio.h>
+#include <asm/arch-rockchip/gpio.h>
+
+/*
+ * ID info:
+ *  ID : Volts : ADC value :   Bucket
+ *  ==   =====   =========   ===========
+ *   0 : 0.102V:        58 :    0 -   81
+ *   1 : 0.211V:       120 :   82 -  150
+ *   2 : 0.319V:       181 :  151 -  211
+ *   3 : 0.427V:       242 :  212 -  274
+ *   4 : 0.542V:       307 :  275 -  342
+ *   5 : 0.666V:       378 :  343 -  411
+ *   6 : 0.781V:       444 :  412 -  477
+ *   7 : 0.900V:       511 :  478 -  545
+ *   8 : 1.023V:       581 :  546 -  613
+ *   9 : 1.137V:       646 :  614 -  675
+ *  10 : 1.240V:       704 :  676 -  733
+ *  11 : 1.343V:       763 :  734 -  795
+ *  12 : 1.457V:       828 :  796 -  861
+ *  13 : 1.576V:       895 :  862 -  925
+ *  14 : 1.684V:       956 :  926 -  989
+ *  15 : 1.800V:      1023 :  990 - 1023
+ */
+static const int id_readings[] = {
+	 81, 150, 211, 274, 342, 411, 477, 545,
+	613, 675, 733, 795, 861, 925, 989, 1023
+};
+
+static int cached_board_id = -1;
+
+#define SARADC_BASE		0xFF100000
+#define SARADC_DATA		(SARADC_BASE + 0)
+#define SARADC_CTRL		(SARADC_BASE + 8)
+
+static u32 get_saradc_value(int chn)
+{
+	int timeout = 0;
+	u32 adc_value = 0;
+
+	writel(0, SARADC_CTRL);
+	udelay(2);
+
+	writel(0x28 | chn, SARADC_CTRL);
+	udelay(50);
+
+	timeout = 0;
+	do {
+		if (readl(SARADC_CTRL) & 0x40) {
+			adc_value = readl(SARADC_DATA) & 0x3FF;
+			goto stop_adc;
+		}
+
+		udelay(10);
+	} while (timeout++ < 100);
+
+stop_adc:
+	writel(0, SARADC_CTRL);
+
+	return adc_value;
+}
+
+static uint32_t get_adc_index(int chn)
+{
+	int i;
+	int adc_reading;
+
+	if (cached_board_id != -1)
+		return cached_board_id;
+
+	adc_reading = get_saradc_value(chn);
+	for (i = 0; i < ARRAY_SIZE(id_readings); i++) {
+		if (adc_reading <= id_readings[i]) {
+			debug("ADC reading %d, ID %d\n", adc_reading, i);
+			cached_board_id = i;
+			return i;
+		}
+	}
+
+	/* should die for impossible value */
+	return 0;
+}
+
+/*
+ * Board revision list: <GPIO4_D1 | GPIO4_D0>
+ *  0b00 - NanoPC-T4
+ *  0b01 - NanoPi M4
+ *
+ * Extended by ADC_IN4
+ * Group A:
+ *  0x04 - NanoPi NEO4
+ *  0x06 - SOC-RK3399
+ *  0x07 - SOC-RK3399 V2
+ *  0x09 - NanoPi R4S 1GB
+ *  0x0A - NanoPi R4S 4GB
+ *
+ * Group B:
+ *  0x21 - NanoPi M4 Ver2.0
+ *  0x22 - NanoPi M4B
+ */
+static int pcb_rev = -1;
+
+void bd_hwrev_init(void)
+{
+#define GPIO4_BASE	0xff790000
+	struct rockchip_gpio_regs *regs = (void *)GPIO4_BASE;
+
+#ifdef CONFIG_SPL_BUILD
+	struct udevice *dev;
+
+	if (uclass_get_device_by_driver(UCLASS_CLK,
+				DM_GET_DRIVER(clk_rk3399), &dev))
+		return;
+#endif
+
+	if (pcb_rev >= 0)
+		return;
+
+	/* D1, D0: input mode */
+	clrbits_le32(&regs->swport_ddr, (0x3 << 24));
+	pcb_rev = (readl(&regs->ext_port) >> 24) & 0x3;
+
+	if (pcb_rev == 0x3) {
+		/* Revision group A: 0x04 ~ 0x13 */
+		pcb_rev = 0x4 + get_adc_index(4);
+
+	} else if (pcb_rev == 0x1) {
+		int idx = get_adc_index(4);
+
+		/* Revision group B: 0x21 ~ 0x2f */
+		if (idx > 0) {
+			pcb_rev = 0x20 + idx;
+		}
+	}
+}
+
+#ifdef CONFIG_SPL_BUILD
+static struct board_ddrtype {
+	int rev;
+	const char *type;
+} ddrtypes[] = {
+	{ 0x00, "lpddr3-samsung-4GB-1866" },
+	{ 0x01, "lpddr3-samsung-4GB-1866" },
+	{ 0x04,   "ddr3-1866" },
+	{ 0x06,   "ddr3-1866" },
+	{ 0x07, "lpddr4-100"  },
+	{ 0x09,   "ddr3-1866" },
+	{ 0x0a, "lpddr4-100"  },
+	{ 0x21, "lpddr4-100"  },
+	{ 0x22,   "ddr3-1866" },
+};
+
+const char *rk3399_get_ddrtype(void) {
+	int i;
+
+	bd_hwrev_init();
+	printf("Board: rev%02x\n", pcb_rev);
+
+	for (i = 0; i < ARRAY_SIZE(ddrtypes); i++) {
+		if (ddrtypes[i].rev == pcb_rev)
+			return ddrtypes[i].type;
+	}
+
+	/* fallback to first subnode (ie, first included dtsi) */
+	return NULL;
+}
+#endif
+
+/* To override __weak symbols */
+u32 get_board_rev(void)
+{
+	return pcb_rev;
+}
+