ramips: add RB750Gr3 native support

This patch adds support of MikroTik RouterBOARD 750Gr3, without the need
to reflashing the bootloader.

Installation through RouterBoot follows the usual MikroTik method
https://openwrt.org/toh/mikrotik/common

Since the image isn't compatible with RouterBOARD 750Gr3 installations
which have replaced the bootloader, the former used userspace boardname
is not added to the SUPPORTED_DEVICES, to prevent a brick while trying
to upgrade to the image with native support.

Signed-off-by: Anton Arapov <arapov@gmail.com>
Signed-off-by: Thibaut VARÈNE <hacks@slashdirt.org>
Signed-off-by: Mathias Kresin <dev@kresin.me>

target/linux/ramips/base-files/etc/board.d/02_network

@@ -222,9 +222,9 @@ ramips_setup_interfaces()
 	jhr-n805r|\
 	jhr-n825r|\
 	jhr-n926r|\
+	mikrotik,rb750gr3|\
 	mikrotik,rbm33g|\
 	mzk-wdpr|\
-	rb750gr3|\
 	rt-n14u|\
 	skylab,skw92a|\
 	tplink,c20-v4|\

target/linux/ramips/base-files/lib/ramips.sh

@@ -415,9 +415,6 @@ ramips_board_detect() {
 	*"R6220")
 		name="r6220"
 		;;
-	*"RB750Gr3")
-		name="rb750gr3"
-		;;
 	*"RE350 v1")
 		name="re350-v1"
 		;;

target/linux/ramips/base-files/lib/upgrade/platform.sh

@@ -13,6 +13,7 @@ platform_pre_upgrade() {
 	local board=$(board_name)
 
 	case "$board" in
+	mikrotik,rb750gr3|\
 	mikrotik,rbm11g|\
 	mikrotik,rbm33g)
 		[ -z "$(rootfs_type)" ] && mtd erase firmware

target/linux/ramips/dts/RB750Gr3.dts

@@ -22,7 +22,7 @@
 	};
 
 	chosen {
-		bootargs = "console=ttyS0,57600";
+		bootargs = "console=ttyS0,115200";
 	};
 
 	gpio-leds {
@@ -89,34 +89,54 @@
 			#size-cells = <1>;
 
 			partition@0 {
-				label = "u-boot";
-				reg = <0x0 0x30000>;
+				label = "RouterBoot";
+				reg = <0x0 0x40000>;
 				read-only;
+				compatible = "fixed-partitions";
+				#address-cells = <1>;
+				#size-cells = <1>;
+
+				partition@0 {
+					label = "bootloader1";
+					reg = <0x0 0xf000>;
+					read-only;
+				};
+
+				hard_config: partition@f000 {
+					label = "hard_config";
+					reg = <0xf000 0x1000>;
+					read-only;
+				};
+
+				partition@10000 {
+					label = "bootloader2";
+					reg = <0x10000 0xf000>;
+					read-only;
+				};
+
+				partition@20000 {
+					label = "soft_config";
+					reg = <0x20000 0x1000>;
+				};
+
+				partition@30000 {
+					label = "bios";
+					reg = <0x30000 0x1000>;
+					read-only;
+				};
 			};
 
-			partition@30000 {
-				label = "u-boot-env";
-				reg = <0x30000 0x10000>;
-				read-only;
-			};
-
-			factory: partition@40000 {
-				label = "factory";
-				reg = <0x40000 0x10000>;
-				read-only;
-			};
-
-			partition@50000 {
-				compatible = "denx,uimage";
+			partition@40000 {
+				compatible = "mikrotik,minor";
 				label = "firmware";
-				reg = <0x50000 0xfb0000>;
+				reg = <0x040000 0xfc0000>;
 			};
 		};
 	};
 };
 
 &ethernet {
-	mtd-mac-address = <&factory 0xe000>;
+	mtd-mac-address = <&hard_config 0x0010>;
 	mtd-mac-address-increment = <1>;
 };
 

target/linux/ramips/image/mt7621.mk

@@ -324,14 +324,6 @@ define Device/netgear_r6350
 endef
 TARGET_DEVICES += netgear_r6350
 
-define Device/rb750gr3
-  DTS := RB750Gr3
-  IMAGE_SIZE := $(ralink_default_fw_size_16M)
-  DEVICE_TITLE := MikroTik RB750Gr3
-  DEVICE_PACKAGES := kmod-usb3 uboot-envtools
-endef
-TARGET_DEVICES += rb750gr3
-
 define Device/MikroTik
   BLOCKSIZE := 64k
   IMAGE_SIZE := 16128k
@@ -343,6 +335,13 @@ define Device/MikroTik
 	append-rootfs | pad-rootfs | append-metadata | check-size $$$$(IMAGE_SIZE)
 endef
 
+define Device/mikrotik_rb750gr3
+  $(Device/MikroTik)
+  DTS := RB750Gr3
+  DEVICE_TITLE := MikroTik RouterBOARD RB750Gr3
+endef
+TARGET_DEVICES += mikrotik_rb750gr3
+
 define Device/mikrotik_rbm33g
   $(Device/MikroTik)
   DTS := RBM33G