How to debug HW startup?

[Mauro Condarelli]

I managed to brick my target.

Situation:
I have a board with a paleolithic (1.1.3) version of u-boot.
I had been testing by loading in ram from USB:
    usb reset; fatload usb 0 80010000 u-boot.bin; go 80010000
and everything was ok.
I changed a few settings (both defconfigs are attached below)
and tried "the real thing"
Unfortunately reflashing the actual boot produced a brick.
It does not utter a single byte.

I will have to reflash the original using an external apparatus
(which I don't have here, so I'll have to take target to another
location, probably tomorrow morning), but question is:
how do I debug such a situation?
What could I have done so wrong?

As You can see I changed only a few settings:

--- configs/vocore_vocore2-ram_defconfig    2020-01-09
16:11:12.568096050 +0100
+++ configs/vocore_vocore2_defconfig    2020-01-09 16:07:10.528267378 +0100
@@ -1,9 +1,12 @@
 CONFIG_MIPS=y
-CONFIG_SYS_TEXT_BASE=0x80010000
+CONFIG_SYS_TEXT_BASE=0x9c000000
 CONFIG_ENV_SIZE=0x00001000
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_ARCH_MTMIPS=y
 CONFIG_BOARD_VOCORE2=y
+CONFIG_BOOT_ROM=y
+CONFIG_ONBOARD_DDR2_SIZE_1024MBIT=y
+CONFIG_ONBOARD_DDR2_CHIP_WIDTH_16BIT=y
 CONFIG_MIPS_BOOT_FDT=y
 CONFIG_ENV_VARS_UBOOT_CONFIG=y
 CONFIG_SYS_BOOT_GET_CMDLINE=y
... in a way that's very similar to boards based on the same SoC
(linkit-smart-7688 and gardena-smart-gateway-mt7688).

In the ancient u-boot I had to remove a header from the RAM
version, but this was not needed with current u-boot.

Did I forget some step?

Any hint welcome
Thanks in advance
Mauro

-------------- next part --------------
CONFIG_MIPS=y
CONFIG_SYS_TEXT_BASE=0x9c000000
CONFIG_ENV_SIZE=0x00001000
CONFIG_NR_DRAM_BANKS=1
CONFIG_ARCH_MTMIPS=y
CONFIG_BOARD_VOCORE2=y
CONFIG_BOOT_ROM=y
CONFIG_ONBOARD_DDR2_SIZE_1024MBIT=y
CONFIG_ONBOARD_DDR2_CHIP_WIDTH_16BIT=y
CONFIG_MIPS_BOOT_FDT=y
CONFIG_ENV_VARS_UBOOT_CONFIG=y
CONFIG_SYS_BOOT_GET_CMDLINE=y
CONFIG_SYS_BOOT_GET_KBD=y
# CONFIG_ARCH_FIXUP_FDT_MEMORY is not set
CONFIG_USE_BOOTARGS=y
CONFIG_LOGLEVEL=8
CONFIG_VERSION_VARIABLE=y
CONFIG_DISPLAY_BOARDINFO_LATE=y
# CONFIG_AUTOBOOT is not set
# CONFIG_BOOTM_NETBSD is not set
# CONFIG_BOOTM_PLAN9 is not set
# CONFIG_BOOTM_RTEMS is not set
# CONFIG_BOOTM_VXWORKS is not set
# CONFIG_CMD_XIMG is not set
CONFIG_CMD_MEMINFO=y
CONFIG_CMD_GPIO=y
CONFIG_RANDOM_UUID=y
# CONFIG_CMD_LOADB is not set
# CONFIG_CMD_LOADS is not set
CONFIG_CMD_MMC=y
CONFIG_CMD_MTD=y
CONFIG_CMD_PART=y
CONFIG_CMD_SPI=y
CONFIG_CMD_USB=y
CONFIG_CMD_WDT=y
CONFIG_CMD_FAT=y
CONFIG_CMD_FS_GENERIC=y
CONFIG_CMD_MTDPARTS=y
CONFIG_MTDIDS_DEFAULT="nor0=spi0.0"
CONFIG_MTDPARTS_DEFAULT="spi0.0:320k(u-boot),2752k(kernel),13304k(filesystem),4k(env),-(factory)"
# CONFIG_ISO_PARTITION is not set
CONFIG_DEFAULT_DEVICE_TREE="vocore_vocore2"
CONFIG_ENV_IS_IN_FAT=y
CONFIG_ENV_FAT_INTERFACE="mmc"
CONFIG_ENV_FAT_DEVICE_AND_PART="0:1"
# CONFIG_NET is not set
# CONFIG_DM_DEVICE_REMOVE is not set
# CONFIG_INPUT is not set
CONFIG_LED=y
CONFIG_LED_BLINK=y
CONFIG_LED_GPIO=y
CONFIG_MMC=y
CONFIG_DM_MMC=y
# CONFIG_MMC_HW_PARTITIONING is not set
CONFIG_MMC_MTK=y
CONFIG_MTD=y
CONFIG_SPI_FLASH_SFDP_SUPPORT=y
CONFIG_SPI_FLASH_GIGADEVICE=y
CONFIG_SPI_FLASH_MTD=y
# CONFIG_DM_ETH is not set
# CONFIG_RAM_ROCKCHIP_DEBUG is not set
CONFIG_SPECIFY_CONSOLE_INDEX=y
CONFIG_CONS_INDEX=3
CONFIG_SPI=y
CONFIG_MT7621_SPI=y
CONFIG_SYSRESET_SYSCON=y
CONFIG_USB=y
CONFIG_DM_USB=y
CONFIG_USB_EHCI_HCD=y
CONFIG_USB_EHCI_GENERIC=y
CONFIG_USB_STORAGE=y
CONFIG_WDT=y
CONFIG_WDT_MT7621=y
CONFIG_LZMA=y
CONFIG_LZO=y
-------------- next part --------------
CONFIG_MIPS=y
CONFIG_SYS_TEXT_BASE=0x80010000
CONFIG_ENV_SIZE=0x00001000
CONFIG_NR_DRAM_BANKS=1
CONFIG_ARCH_MTMIPS=y
CONFIG_BOARD_VOCORE2=y
CONFIG_MIPS_BOOT_FDT=y
CONFIG_ENV_VARS_UBOOT_CONFIG=y
CONFIG_SYS_BOOT_GET_CMDLINE=y
CONFIG_SYS_BOOT_GET_KBD=y
# CONFIG_ARCH_FIXUP_FDT_MEMORY is not set
CONFIG_USE_BOOTARGS=y
CONFIG_LOGLEVEL=8
CONFIG_VERSION_VARIABLE=y
CONFIG_DISPLAY_BOARDINFO_LATE=y
# CONFIG_AUTOBOOT is not set
# CONFIG_BOOTM_NETBSD is not set
# CONFIG_BOOTM_PLAN9 is not set
# CONFIG_BOOTM_RTEMS is not set
# CONFIG_BOOTM_VXWORKS is not set
# CONFIG_CMD_XIMG is not set
CONFIG_CMD_MEMINFO=y
CONFIG_CMD_GPIO=y
CONFIG_RANDOM_UUID=y
# CONFIG_CMD_LOADB is not set
# CONFIG_CMD_LOADS is not set
CONFIG_CMD_MMC=y
CONFIG_CMD_MTD=y
CONFIG_CMD_PART=y
CONFIG_CMD_SPI=y
CONFIG_CMD_USB=y
CONFIG_CMD_WDT=y
CONFIG_CMD_FAT=y
CONFIG_CMD_FS_GENERIC=y
CONFIG_CMD_MTDPARTS=y
CONFIG_MTDIDS_DEFAULT="nor0=spi0.0"
CONFIG_MTDPARTS_DEFAULT="spi0.0:320k(u-boot),2752k(kernel),13304k(filesystem),4k(env),-(factory)"
# CONFIG_ISO_PARTITION is not set
CONFIG_DEFAULT_DEVICE_TREE="vocore_vocore2"
CONFIG_ENV_IS_IN_FAT=y
CONFIG_ENV_FAT_INTERFACE="mmc"
CONFIG_ENV_FAT_DEVICE_AND_PART="0:1"
# CONFIG_NET is not set
# CONFIG_DM_DEVICE_REMOVE is not set
# CONFIG_INPUT is not set
CONFIG_LED=y
CONFIG_LED_BLINK=y
CONFIG_LED_GPIO=y
CONFIG_MMC=y
CONFIG_DM_MMC=y
# CONFIG_MMC_HW_PARTITIONING is not set
CONFIG_MMC_MTK=y
CONFIG_MTD=y
CONFIG_SPI_FLASH_SFDP_SUPPORT=y
CONFIG_SPI_FLASH_GIGADEVICE=y
CONFIG_SPI_FLASH_MTD=y
# CONFIG_DM_ETH is not set
# CONFIG_RAM_ROCKCHIP_DEBUG is not set
CONFIG_SPECIFY_CONSOLE_INDEX=y
CONFIG_CONS_INDEX=3
CONFIG_SPI=y
CONFIG_MT7621_SPI=y
CONFIG_SYSRESET_SYSCON=y
CONFIG_USB=y
CONFIG_DM_USB=y
CONFIG_USB_EHCI_HCD=y
CONFIG_USB_EHCI_GENERIC=y
CONFIG_USB_STORAGE=y
CONFIG_WDT=y
CONFIG_WDT_MT7621=y
CONFIG_LZMA=y
CONFIG_LZO=y