board: qualcomm: rtwo bootcmd to chainload pmOS FIT

Custom bootcmd/bootargs for the Motorola Edge 40 Pro (rtwo, SM8550).
The Motorola ABL loads this U-Boot as its "kernel" and always fills
/chosen/linux,initrd-start with the RAM address of whatever it loaded
as "ramdisk" (standard Android/GKI boot protocol). We package a FIT
image (mainline pmOS kernel + dtb + initramfs) as that ramdisk, so
bootcmd reads $prevbl_initrd_start_addr (populated by
CONFIG_SAVE_PREV_BL_INITRAMFS_START_ADDR from that same DT property)
and does `bootm` on it, with a menu/bootefi fallback if the FIT boot
fails.

Part of the rtwo bring-up: see project notes rtwo-uboot-chainload for
the full mechanism and why this replaced booting the mainline kernel
directly from the Motorola ABL.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015ADQrjdgE8awSA7TSaGgfr

board/qualcomm/qcom-phone.env

@@ -21,7 +21,15 @@ serial_gadget=setenv stdin serial,button-kbd,usbacm; \
 # bootretry will run this command over and over, if we fail once
 # then bail out to the boot menu instead (with a pause to read
 # the error message)
-bootcmd=bootefi bootmgr; pause; run menucmd
+#
+# rtwo (Motorola Edge 40 Pro, SM8550): the ABL loads the FIT image
+# (mainline Image + dtb + initramfs) into the ramdisk slot of the
+# Android boot.img. The ABL writes that address into
+# /chosen/linux,initrd-start of the fdt it hands us, and U-Boot saves
+# it as $prevbl_initrd_start_addr (CONFIG_SAVE_PREV_BL_INITRAMFS_START_ADDR).
+# Try that first; only fall back to the phone menu if it fails.
+pmos_bootargs=earlycon console=ttyMSM0,115200n8 panic=5 pmos.debug-shell clk_ignore_unused pd_ignore_unused regulator_ignore_unused allow_mismatched_32bit_el0 pmos_boot_uuid=d4373976-057c-4cf3-a43d-00734001b405 pmos_root_uuid=09804032-85bb-4d57-95a5-00d1965fb10f pmos_rootfsopts=defaults
+bootcmd=setenv bootargs $pmos_bootargs; echo pmOS: booting FIT at prevbl_initrd_start_addr=$prevbl_initrd_start_addr; bootm $prevbl_initrd_start_addr; echo pmOS: bootm failed; bootefi bootmgr; pause; run menucmd
 
 # When entering the menu (either from button press or failed boot)
 # remap bootcmd so it will re-open the menu and we won't get stuck
@@ -29,17 +37,19 @@ bootcmd=bootefi bootmgr; pause; run menucmd
 menucmd=setenv bootcmd run menucmd; bootmenu -1
 
 # Pause is used so the output can be read on the display
-bootmenu_0=Boot=bootefi bootmgr; pause
-bootmenu_1=Enable serial console gadget=run serial_gadget
-bootmenu_2=Enable USB mass storage=echo "Press any key to exit UMS mode"; ums 0 scsi 0
-bootmenu_3=Enable fastboot mode=run fastboot
+bootmenu_0=Boot pmOS mainline (FIT)=setenv bootargs $pmos_bootargs; bootm $prevbl_initrd_start_addr; pause
+bootmenu_1=Boot=bootefi bootmgr; pause
+bootmenu_2=Enable serial console gadget=run serial_gadget
+bootmenu_3=Enable USB mass storage=echo "Press any key to exit UMS mode"; ums 0 scsi 0
+bootmenu_4=Enable fastboot mode=echo "Press any key to exit fastboot mode"; run fastboot
 # Disabling bootretry means we'll just drop the shell
-bootmenu_4=Drop to shell=setenv bootretry -1
-bootmenu_5=Reset device=reset
-bootmenu_6=Dump clocks=clk dump; pause
-bootmenu_7=Dump environment=printenv; pause
-bootmenu_8=Board info=bdinfo; pause
-bootmenu_9=Dump bootargs=fdt addr $fdt_addr_r; fdt print /chosen bootargs; pause
+bootmenu_5=Drop to shell=setenv bootretry -1
+bootmenu_6=Reset device=reset
+bootmenu_7=Dump clocks=clk dump; pause
+bootmenu_8=Dump environment=printenv; pause
+bootmenu_9=Board info=bdinfo; pause
+bootmenu_10=Dump bootargs=fdt addr $fdt_addr_r; fdt print /chosen bootargs; pause
+bootmenu_11=Power off=poweroff
 
 # Allow holding the volume down button while U-Boot loads to enter
 # the boot menu