mb/lattepanda: Add support for LattePanda Mu

Add initial support for the LattePanda Mu board, which features:
  - Intel Alder Lake-N N100 processor
  - Samsung K3LK7K70BM-BGCP, 8GB LPDDR5 memory
  - Samsung KLMCG2UCTA-B041, 64GB eMMC storage
  - SO-DIMM 260-pin connector for function expansion

This commit includes:
  - Basic board configuration
  - Memory initialization
  - Essential I/O setup
  - Used UEFITool NE alpha 68 (Nov 4 2023) to extract data.vbt file
    from original BIOS
  - BIOS download link: https://github.com/LattePandaTeam/LattePanda-Mu
    located at "./Softwares/BIOS/DFLT/LP-BS-S70NC1R200-SR-A.bin.zip"

Test Environment:
  - Carrier Board: Lite
  - Payload: mrchromebox/edk2
  - EDK2 Version: uefipayload_202309

Test result
Passed:
  - Windows 11 boot from eMMC
  - Install Ubuntu 24.04 on NVMe SSD
  - Ubuntu 24.04 boot from NVMe SSD
  - USB 3.0/2.0 functionality
  - Realtek RTL8111H-CG-RH Ethernet
  - HDMI Display
    - Audio over HDMI work in Ubuntu 24.04

Known Issues:
  - S3 sleep mode non-functional
  - Power-on after shutdown requires power removal
  - SuperIO UART not detected in Windows 11
  - Audio over HDMI not work in Windows 11
  - Windows 11 BSOD occurs with NVMe SSD installed:
    - Stop code: Machine Check Exception
  - NVMe SSD not working on Windows 11, except when:
    - KDNet Debugging enabled on NIC during boot
    - SSD becomes functional in this scenario

Change-Id: I79696bdd837a221860b32f54629212c3346dca66
Signed-off-by: KunYi Chen <kunyi.chen@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83719
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/mainboard/lattepanda/mu/mainboard.c b/src/mainboard/lattepanda/mu/mainboard.c
new file mode 100644
index 0000000000..4270f050c7
--- /dev/null
+++ b/src/mainboard/lattepanda/mu/mainboard.c
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <baseboard/gpio.h>
+#include <baseboard/variants.h>
+#include <cpu/cpu.h>
+#include <cpu/intel/cpu_ids.h>
+#include <device/device.h>
+#include <drivers/intel/gma/opregion.h>
+#include <fw_config.h>
+#include <smbios.h>
+#include <soc/gpio.h>
+#include <stdint.h>
+#include <stdio.h>
+
+const char *smbios_system_sku(void)
+{
+	static char sku_str[7] = "";
+	uint8_t sku_id = 1;
+
+	snprintf(sku_str, sizeof(sku_str), "sku%u", sku_id);
+	return sku_str;
+}
+
+static void mainboard_init(void *chip_info)
+{
+	variant_configure_gpio_pads();
+	variant_devtree_update();
+}
+
+struct chip_operations mainboard_ops = {
+	.init = mainboard_init,
+};