flake: configure u-boot to autoboot kernel

Signed-off-by: Florian Agbuya <fa@m-labs.ph>

flake.nix

@@ -199,8 +199,20 @@
         preConfigure = ''
           export DEVICE_TREE=zynq-${board}
         '';
-        extraMeta.platforms = ["armv7l-linux"];
-        filesToInstall = ["u-boot.elf"];
+        extraConfig = ''
+          CONFIG_AUTOBOOT=y
+          CONFIG_BOOTCOMMAND="${builtins.replaceStrings [ "\n" ] [ "; " ] ''
+            setenv bootargs 'root=/dev/mmcblk0p2 console=ttyPS0,115200n8 systemConfig=${builtins.unsafeDiscardStringContext not-os-configured.config.system.build.toplevel}'
+            fatload mmc 0 0x6400000 uImage
+            fatload mmc 0 0x8000000 devicetree.dtb
+            fatload mmc 0 0xA400000 uramdisk.image.gz
+            bootm 0x6400000 0xA400000 0x8000000
+          ''}"
+          CONFIG_BOOTDELAY=0
+          CONFIG_USE_BOOTCOMMAND=y
+        '';
+        extraMeta.platforms = [ "armv7l-linux" ];
+        filesToInstall = [ "u-boot.elf" ];
       };
 
       bootimage = { board ? "zc706" }: pkgs.runCommand "${board}-bootimage"