uboot-rockchip: add FriendlyARM NanoPC T4 support

Add support for the FriendlyARM NanoPC T4.
Reduce memory frequency to avoid random crash.

Signed-off-by: Lu jicong <jiconglu58@gmail.com>
Signed-off-by: Tianling Shen <cnsztl@immortalwrt.org>
(cherry picked from commit eb025412a1)

package/boot/uboot-rockchip/Makefile

@@ -97,6 +97,13 @@ define U-Boot/guangmiao-g4c-rk3399
     huake_guangmiao-g4c
 endef
 
+define U-Boot/nanopc-t4-rk3399
+  $(U-Boot/rk3399/Default)
+  NAME:=NanoPC T4
+  BUILD_DEVICES:= \
+    friendlyarm_nanopc-t4
+endef
+
 define U-Boot/nanopi-r4s-rk3399
   $(U-Boot/Default/rk3399)
   NAME:=NanoPi R4S
@@ -186,6 +193,7 @@ endef
 
 UBOOT_TARGETS := \
   guangmiao-g4c-rk3399 \
+  nanopc-t4-rk3399 \
   nanopi-r4s-rk3399 \
   nanopi-r4se-rk3399 \
   nanopi-r4s-enterprise-rk3399 \

package/boot/uboot-rockchip/patches/105-nanopc-t4-fix-memory-unstability.patch

@@ -0,0 +1,24 @@
+From 445502bc21ecf1b5120faee785cea578b810c759 Mon Sep 17 00:00:00 2001
+From: Lu jicong <jiconglu58@gmail.com>
+Date: Wed, 5 Jul 2023 17:13:55 +0800
+Subject: [PATCH] rockchip: rk3399: nanopc-t4: use 1600MHz sdram config
+
+Current 1866MHz sdram config is too high for NanoPC-T4.
+On this frequency, its lpddr3 sdram becomes unstable,
+causing memtest failures and random kernel crashes.
+
+Signed-off-by: Lu jicong <jiconglu58@gmail.com>
+---
+ arch/arm/dts/rk3399-nanopc-t4-u-boot.dtsi | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/arch/arm/dts/rk3399-nanopc-t4-u-boot.dtsi b/arch/arm/dts/rk3399-nanopc-t4-u-boot.dtsi
+index 17201bcf41..8b6c9059ab 100644
+--- a/arch/arm/dts/rk3399-nanopc-t4-u-boot.dtsi
++++ b/arch/arm/dts/rk3399-nanopc-t4-u-boot.dtsi
+@@ -4,4 +4,4 @@
+  */
+ 
+ #include "rk3399-nanopi4-u-boot.dtsi"
+-#include "rk3399-sdram-lpddr3-samsung-4GB-1866.dtsi"
++#include "rk3399-sdram-lpddr3-4GB-1600.dtsi"