Just to finally confirm that the U-Boot parameters were not in any way affection the APC boot – and therefore that the problem was in the APC’s kernel configuration, probably with the CONFIG_CMDLINE parameter in the original kernel’s .config file – I removed all the U-Boot parameters, as follows:

WMT # setenv wmt.display.logoaddr; setenv logocmd; setenv wmt.gpo.lcd; setenv wmt.i2c.param; setenv wmt.eth.param; setenv wmt.ui.storage; setenv wmt.vd.debug; setenv wmt.camera.param; setenv wmt.gpo.cmos; setenv wmt.webview.param; setenv wmt.audio.i2s; setenv wmt.audio.rate; setenv wmt.pwbn.param; setenv wmt.l2c.param; setenv wmt.display.hdmi.vmode; setenv wmt.sd0.param; setenv wmt.sd1.param; setenv wmt.sd2.param; setenv wmt.ge.param; setenv android_bootargs; setenv wmt.mali.param; setenv wmt.wifi.param; setenv wmt.gpo.wifi; setenv wmt.nfc.mtd.u-boot-logo; setenv wmt.nfc.mtd.kernel-logo; setenv wmt.plla.param; setenv wmt.io.bat; setenv wmt.io.ts;

WMT # setenv wmt.io.gsensor; setenv wmt.usb.param; setenv wmt.camera.i2c_gpio; setenv memtotal; setenv mmcid; setenv mbsize; setenv scriptcmd; setenv logocmd; setenv mmcargs; setenv mmcboot; setenv nandargs; setenv nandboot; setenv bootcmd; setenv kernel-NAND_mtd; setenv kernel-NAND_ofs; setenv kernel-NAND_len; setenv initrd-NAND_mtd; setenv initrd-NAND_ofs; setenv initrd-NAND_len; setenv filesystem-NAND_mtd; setenv filesystem-NAND_ofs; setenv filesystem-NAND_len; setenv stdin; setenv stdout; setenv stderr; setenv ver; setenv mmcboot; setenv usbboot; setenv filesystem-mmc_mtd; setenv filesize; setenv uboot_usb; setenv ipaddr; setenv ethaddr; setenv serverip; setenv gatewayip; setenv netmask; setenv usbargs;

- got message:
Can't delete "stdin"
Can't delete "stdout"
Can't delete "stderr"

WMT # printenv
stdin=serial
stdout=serial
stderr=serial

The command has to be split into two parts, as there appears to be a limit to the length of a single U-Boot command..

I then entered the minimum U-Boot parameters necessary for USB boot, and then booted the APC.

WMT # setenv wmt.usb.param “11:3”

WMT # usb reset

WMT # root=/dev/sdb2

WMT # rootfstype=ext2

WMT # fatload usb 1:1 0x1000000 uzImage.bin 400000

WMT # fatload usb 1:1 0x1400000 initrd.gz 400000

WMT # bootm 0x1000000

The result was a kernel panic, as before, as the system was – once again – only expecting a rootfs on on of the /dev/mtdblockNN devices..

There seems little that can now be done to fix this at the moment, as the only solution would be a different version of the APC kernel that does not have the ‘root= ‘ parameter hard-coded at compile time.    Of course, the best solution would be a complete set of source code for the entire kernel, including WMT drivers..