bootloader: Add u-boot-rpi4-arm64-bootloader.

* rosenthal/bootloader/u-boot.scm: New file.
(%rpi4-arm64-boot-config,install-rpi4-arm64-bootloader)
(u-boot-rpi4-arm64-bootloader): New variables.

rosenthal/bootloader/u-boot.scm

@@ -0,0 +1,56 @@
+;; SPDX-FileCopyrightText: 2022 Hilton Chain <hako@ultrarare.space>
+;;
+;; SPDX-License-Identifier: GPL-3.0-or-later
+
+(define-module (rosenthal bootloader u-boot)
+  #:use-module (gnu bootloader)
+  #:use-module (gnu bootloader u-boot)
+  #:use-module (guix gexp)
+  #:use-module (rosenthal packages bootloaders)
+  #:export (u-boot-rpi4-arm64-bootloader))
+
+;; Autoload Nonguix*, so we only have a soft dependency.
+;; * <https://gitlab.com/nonguix/nonguix>
+(module-autoload! (current-module)
+                  '(nongnu packages linux) '(raspberrypi-firmware))
+
+(define %rpi4-arm64-boot-config
+  (plain-file "config.txt" (format #f "~
+enable_uart=1
+avoid_warnings=1
+arm_64bit=1
+kernel=u-boot.bin
+")))
+
+;; https://www.raspberrypi.com/documentation/computers/configuration.html#the-boot-folder
+(define install-rpi4-arm64-bootloader
+  #~(lambda (bootloader device mount-point)
+      (let ((u-boot (string-append bootloader "/libexec/u-boot.bin"))
+            (install-dir (string-append mount-point "/boot")))
+        ;; Install raspberrypi-firmware
+        (for-each (lambda (file)
+                    (install-file
+                     (string-append #$raspberrypi-firmware "/" file) install-dir))
+                  '(;; VideoCore firmwares
+                    "start4.elf"        ;basic
+                    "start4x.elf"       ;camera drivers and codec
+                    "start4cd.elf"      ;cut-down
+                    "start4db.elf"      ;debug
+                    ;; Linker files
+                    "fixup4.dat"
+                    "fixup4x.dat"
+                    "fixup4cd.dat"
+                    "fixup4db.dat"
+                    ;; Device Tree Overlays (for Raspberry Pi's bootloader)
+                    "bcm2711-rpi-4-b.dtb"))
+        ;; Install u-boot
+        (install-file u-boot install-dir)
+        ;; Raspberry Pi's bootloader configuration
+        (copy-file #$%rpi4-arm64-boot-config
+                   (string-append install-dir "/config.txt")))))
+
+(define u-boot-rpi4-arm64-bootloader
+  (bootloader
+   (inherit u-boot-bootloader)
+   (package u-boot-rpi-arm64)
+   (installer install-rpi4-arm64-bootloader)))