mips: Add basic MediaTek MT7620/88 support

This patch adds basic support for the MediaTek MT7620/88 SoCs. Parts of
the code is copied from the MediaTek GitHub repository:

https://github.com/MediaTek-Labs/linkit-smart-uboot.git

The mt7628a.dtsi file is imported from Linux v4.17.

Support for the LinkIt Smart 7688 module and the Gardena Smart Gateway
both based on the MT7688 will be added in further patches.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/mips/mach-mt7620/cpu.c b/arch/mips/mach-mt7620/cpu.c
new file mode 100644
index 0000000..457f09f
--- /dev/null
+++ b/arch/mips/mach-mt7620/cpu.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 Stefan Roese <sr@denx.de>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <ram.h>
+#include <asm/io.h>
+#include <linux/io.h>
+#include <linux/sizes.h>
+#include "mt76xx.h"
+
+#define STR_LEN			6
+
+#ifdef CONFIG_BOOT_ROM
+int mach_cpu_init(void)
+{
+	ddr_calibrate();
+
+	return 0;
+}
+#endif
+
+int dram_init(void)
+{
+	gd->ram_size = get_ram_size((void *)CONFIG_SYS_SDRAM_BASE, SZ_256M);
+
+	return 0;
+}
+
+int print_cpuinfo(void)
+{
+	static const char * const boot_str[] = { "PLL (3-Byte SPI Addr)",
+						 "PLL (4-Byte SPI Addr)",
+						 "XTAL (3-Byte SPI Addr)",
+						 "XTAL (4-Byte SPI Addr)" };
+	const void *blob = gd->fdt_blob;
+	void __iomem *sysc_base;
+	char buf[STR_LEN + 1];
+	fdt_addr_t base;
+	fdt_size_t size;
+	char *str;
+	int node;
+	u32 val;
+
+	/* Get system controller base address */
+	node = fdt_node_offset_by_compatible(blob, -1, "ralink,mt7620a-sysc");
+	if (node < 0)
+		return -FDT_ERR_NOTFOUND;
+
+	base = fdtdec_get_addr_size_auto_noparent(blob, node, "reg",
+						  0, &size, true);
+	if (base == FDT_ADDR_T_NONE)
+		return -EINVAL;
+
+	sysc_base = ioremap_nocache(base, size);
+
+	str = (char *)sysc_base + MT76XX_CHIPID_OFFS;
+	snprintf(buf, STR_LEN + 1, "%s", str);
+	val = readl(sysc_base + MT76XX_CHIP_REV_ID_OFFS);
+	printf("CPU:   %-*s Rev %ld.%ld - ", STR_LEN, buf,
+	       (val & GENMASK(11, 8)) >> 8, val & GENMASK(3, 0));
+
+	val = (readl(sysc_base + MT76XX_SYSCFG0_OFFS) & GENMASK(3, 1)) >> 1;
+	printf("Boot from %s\n", boot_str[val]);
+
+	return 0;
+}