Outline

IMX Serial Download Protocol (SDP)

The iMX processors internal boot ROM handles the first boot stage in order to be able to boot from a variety of devices (uSD, NAND, NOR, SPI, SATA, etc). One of the boot devices, referred to as the 'Serial Downloader Protocol' provides an API over USB OTG. Therefore an application can reside on a host PC that will can control the boot of the iMX as long as you can get the iMX to boot in this mode (referred to as 'BOOT_MODE0'). During the internal ROM's boot, a watchdog is used such that a corrupt or non-existent boot media will result in attempting to boot via SDP. This may be useful if you are working with a board that has an unprogrammed or misprogrammed FLASH device which also has access to USB OTG.

Booting Venice U-Boot over SDP with uuu

NXP provides 'uuu' (Universal Update Utility) which is an evolution of the old Freescale MFGtools. The most important update is that it is supported under Linux instead of Windows only.

For i.MX SoC's we use a 2-stage boot firmware comprised of the Secondary Program Loader (SPL) (provided by U-Boot) as well as U-Boot proper. Each stage is loaded separately as seen below in the examples. While no special code support is needed for the SPL boot over SDP, in order for the SPL to implement SDP to boot to U-Boot proper you need to have the following enabled in U-Boot:

• CONFIG_SPL_USB_HOST_SUPPORT=y
• CONFIG_SPL_USB_GADGET=y
• CONFIG_SPL_USB_SDP_SUPPORT=y
• CONFIG_CMD_USB_SDP=y (only if you want the 'sdp' command in U-Boot'

Linux Install:

wget https://github.com/NXPmicro/mfgtools/releases/download/uuu_1.4.69/uuu
chmod +x uuu
sudo mv uuu /usr/local/bin

Examples: First, activate SDP in the bootloader on the Gateworks SBC:

• Invoke SDP while in U-Boot on the Gateworks SBC:

  u-boot=> sdp 0
  SDP: initialize...
  SDP: handle requests...
  

• List SDP devices on the USB bus on the Linux host PC (desktop/laptop):

  $ uuu -lsusb # list compatible devices on the USB bus in SDP mode
  uuu (Universal Update Utility) for nxp imx chips -- libuuu_1.4.69-0-g63b1d3c
  
  Connected Known USB Devices
  Path Chip Pro Vid Pid BcdVersion
  ==================================================
  3:2 MX8MM SDP: 0x1FC9 0x0134 0x0101
  

• Boot Venice U-Boot over SDP (using flash.bin and u-boot.itb):
  • Linux host:

    $ sudo uuu flash.bin && sudo uuu SDPV: write -f u-boot.itb -addr 0x42000000 && sudo uuu SDPV: jump -addr 0x42000000
    uuu (Universal Update Utility) for nxp imx chips -- libuuu_1.4.139-0-g1a8f760
    
    Success 1    Failure 0                                                         
                                                                                    
                                                                                    
    2:13     2/ 2 [Done                                  ] SDP: done                
    
    
    uuu (Universal Update Utility) for nxp imx chips -- libuuu_1.4.139-0-g1a8f760
    
    Success 0    Failure 0                                                         
                                                                                    
                                                                                    
    2:13     1/ 1 [=================100%=================] SDPV: write -f u-boot.itb
    Okay
    
    
    
    uuu (Universal Update Utility) for nxp imx chips -- libuuu_1.4.139-0-g1a8f760
    
    Success 0    Failure 0                                                         
                                                                                    
                                                                                    
    2:13     1/ 1 [=================100%=================] SDPV: jump -addr 0x420000
    Okay
    

  • Target

    U-Boot SPL 2021.07-00066-g7cc5a04f34ab (Dec 06 2021 - 14:56:21 -0800)
    GSC     : v61 0x1d6f RST:VIN Thermal Protection Disabled
    Model   : GW7211-00-CB
    Serial  : 852420
    MFGDate : 11-19-2021
    RTC     : 1
    PMIC    : MP5416
    DRAM    : LPDDR4 1 GiB
    WDT:   Started with servicing (60s timeout)
    Trying to boot from USB SDP
    SDP: initialize...
    SDP: handle requests...
    Downloading file of size 968812 to 0x42000000... done
    Jumping to header at 0x42000000
    Header Tag is not an IMX image
    Found header at 0x42000000
    DTB     : imx8mm-venice-gw72xx-0x
    NOTICE:  BL31: v2.4(release):f884ad7b0ba2
    NOTICE:  BL31: Built : 13:06:09, Oct 20 2021
    
    
    U-Boot 2021.07-00066-g7cc5a04f34ab (Dec 06 2021 - 14:56:21 -0800)
    
    CPU:   Freescale i.MX8MMQ rev1.0 1600 MHz (running at 1200 MHz)
    CPU:   Industrial temperature grade (-40C to 105C) at 31C
    Reset cause: POR
    Model: Gateworks Venice GW72xx-0x i.MX8MM Development Kit
    DRAM:  1 GiB
    temp    : 23.6C
    vdd_bat : 0.000V
    vdd_vin : 16.932V
    vdd_adc1: 0.000V
    vdd_adc2: 0.000V
    vdd_dram: 1.097V
    vdd_1p2 : 1.192V
    vdd_1p0 : 0.982V
    vdd_2p5 : 2.470V
    vdd_3p3 : 3.254V
    vdd_0p95: 0.949V
    vdd_1p8 : 1.801V
    vdd_gsc : 2.942V
    WDT:   Started with servicing (60s timeout)
    MMC:   FSL_SDHC: 1, FSL_SDHC: 2
    Loading Environment from MMC... MMC Device 0 not found
    *** Warning - No MMC card found, using default environment
    
    In:    serial
    Out:   serial
    Err:   serial
    Net:   DP83867 eth0: ethernet@30be0000 [PRIME]
    GSC     : boot watchdog disabled
    Hit any key to stop autoboot:  0 
    u-boot=> 
    

Note in order to force booting from SDP you must erase the eMMC SPL code (ie 'mmc dev 2 && mmc erase 0 8000) as the default boot cfg fuses are set to boot from eMMC.