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Introduction
Flashing an eMMC of produced board is one of the crucial manufacturing procedures. This post series presents how one can take advantage of i.MX6 features and open source tools to prepare themselves with quite robust and easy to use process.
Target reference platform is Hummingboard Edge.
General concept
The general concept is inspired by this great bootlin (former FreeElectrons) post: I’ve run into some issues while trying to do something similar on Hummingbard Edge, so decided to share my experience.
The general flow looks like:
- Load
U-Bootto DDR using Serial Download Protocol U-Bootenters fastboot mode- Pull in the image via fastboot protocol
In the first post, we will focus on loading U-Boot to DDR using SDP.
Hardware preparation
Before we start, we need to prepare hardware first. HB Edge has USBOTG signals connected to the upper back USB-A connector:
To utilize it we should prepare cable as suggested by the SolidRun wiki
They suggest cutting two USB cables in half to create USB-A male-male cable. To make things easier we can buy one of those directly. An example of such is this one
We still need one more rework:
- Remove the main insulation from the middle of the cable,
- Cut the power wire (usually the read one),
- Solder it back with additional series resistance. SolidRun suggest to use 1-10 Ohms. I am using 2x10 Ohm resistors in parallel which gives me around 5 Ohms.
Resistors soldered on prototype board:
Additional series resistance in power wire path:
Connect USB A host to host cable to USB OTG port (upper port of U5 USB connector on HB Edge board).
Now we should check whether the cable was prepared correctly. If it is, the USB device should be detected as Freescale SoC in Recovery Mode:
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Bus 002 Device 002: ID 15a2:0061 Freescale Semiconductor, Inc. i.MX 6Solo/6DualLite SystemOnChip in RecoveryMode |
It may be convenient to set up an udev rule right away, so we can have access
to device as a user later:
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echo 'SUBSYSTEM =="usb", ATTRS{idVendor}=="15a2", ATTRS{idProduct}=="0061" , MODE="0666"'
| sudo tee /etc/udev/rules.d/51-fsl-flashing.rules |
imx-usb-loader
This is an open-source alternative to NXP mfgtool, which allows sending
binaries over UART or USB.
Getting imx_usb_loader:
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sudo apt-get install libusb-dev libusb-1.0 git clone git@github.com:boundarydevices/imx_usb_loader.git cd imx_usb_loader make |
Output are 2 files: imx_uart and imx_usb that allow to send files to
platform using UART or USB respectively.
imx_usb_loader is able to download a single file u-boot.imx. In case of
boards with SPL support, we have 2 binaries: SPL and u-boot.img. Loading
of both of them is possible using imx_usb_loader, but it is required to take
advantage of the
U-Boot Serial Download Protocol support
U-Boot SDP support was introduced in October 2017. So we need at least v2017.11 release. I’m using the most recent v2018.01.
Following additional configuration options have to be selected to enable SDP support in U-Boot:
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CONFIG_SPL_USB_HOST_SUPPORT=y CONFIG_SPL_USB_GADGET_SUPPORT=y CONFIG_SPL_USB_SDP_SUPPORT=y CONFIG_USB_GADGET=y CONFIG_USB_GADGET_DOWNLOAD=y CONFIG_USB_FUNCTION_SDP=y |
Load SPL and u-boot.img separately
- Copy
SPLandu-boot.imgoutput files to the root directory of theimx_usb_loadertool - Send
SPLvia USB:./imx_usb SPL
output:
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config file <.//imx_usb.conf> vid=0x066f pid=0x3780 file_name=mx23_usb_work.conf vid=0x15a2 pid=0x004f file_name=mx28_usb_work.conf vid=0x15a2 pid=0x0052 file_name=mx50_usb_work.conf vid=0x15a2 pid=0x0054 file_name=mx6_usb_work.conf vid=0x15a2 pid=0x0061 file_name=mx6_usb_work.conf vid=0x15a2 pid=0x0063 file_name=mx6_usb_work.conf vid=0x15a2 pid=0x0071 file_name=mx6_usb_work.conf vid=0x15a2 pid=0x007d file_name=mx6_usb_work.conf vid=0x15a2 pid=0x0080 file_name=mx6_usb_work.conf vid=0x1fc9 pid=0x0128 file_name=mx6_usb_work.conf vid=0x15a2 pid=0x0076 file_name=mx7_usb_work.conf vid=0x1fc9 pid=0x0126 file_name=mx7ulp_usb_work.conf vid=0x15a2 pid=0x0041 file_name=mx51_usb_work.conf vid=0x15a2 pid=0x004e file_name=mx53_usb_work.conf vid=0x15a2 pid=0x006a file_name=vybrid_usb_work.conf vid=0x066f pid=0x37ff file_name=linux_gadget.conf vid=0x1b67 pid=0x4fff file_name=mx6_usb_sdp_spl.conf vid=0x0525 pid=0xb4a4 file_name=mx6_usb_sdp_spl.conf config file <.//mx6_usb_work.conf> parse .//mx6_usb_work.conf Trying to open device vid=0x15a2 pid=0x0061 Interface 0 claimed HAB security state: development mode (0x56787856) == work item filename SPL load_size 0 bytes load_addr 0x00000000 dcd 1 clear_dcd 0 plug 1 jump_mode 2 jump_addr 0x00000000 == end work item No dcd table, barker=402000d1 loading binary file(SPL) to 00907400, skip=0, fsize=ac00 type=aa <<<44032, 44032 bytes>>> succeeded (status 0x88888888) jumping to 0x00907400 |
- HB serial console output will show:
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U-Boot SPL 2018.01-00001-gceb4ce4f78fb-dirty (Jan 16 2018 - 15:04:11) Trying to boot from USB SDP SDP: initialize... SDP: handle requests... |
Notice that once SPL is loaded, and target board enters SDP handler state,
the USB device seen by host PC will change.
In my case it changed from:
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Bus 003 Device 013: ID 15a2:0061 Freescale Semiconductor, Inc. i.MX 6Solo/6DualLite SystemOnChip in RecoveryMode |
to:
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Bus 003 Device 014: ID 0000:0fff |
It does not look like a proper USB device VID / PID pair.
Even if we set those in imx_usb.conf:
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echo '0x0000:0x0fff, mx6_usb_sdp_spl.conf' >> imx_usb.conf |
We are getting following error message from the tool:
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vid/pid cannot be 0: mx6_usb_sdp_spl.conf [0x0000:0x0fff, mx6_usb_sdp_spl.conf ] no matching USB device found |
The
U-Boot SDP documentation
states that those values should be set by configuration options:
CONFIG_G_DNL_(VENDOR|PRODUCT)_NUM and it should default to:
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0x1b67:0x4fff, mx6_usb_sdp_spl.conf |
Grepping U-Boot sources shows only a few of those options in some of the
board config files:
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./configs/chromebook_minnie_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/fennec-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/rock2_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/tinker-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/phycore-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/evb-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/chromebit_mickey_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/chromebook_jerry_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/popmetal-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/miqi-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/vyasa-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x2207 ./configs/firefly-rk3288_defconfig:CONFIG_G_DNL_VENDOR_NUM=0x220 |
Quick search through configuration options shows that gadget USB VID / PID is set through following options:
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config USB_GADGET_VENDOR_NUM hex "Vendor ID of the USB device" default 0x1f3a if ARCH_SUNXI default 0x0 help Vendor ID of the USB device emulated, reported to the host device. This is usually the board or SoC vendor's, unless you've registered for one. config USB_GADGET_PRODUCT_NUM hex "Product ID of the USB device" default 0x1010 if ARCH_SUNXI default 0x0 help Product ID of the USB device emulated, reported to the host device. |
The strange thing to me is that PID defaults to 0x0, while in my case it is
detected as 0x0000:0x0fff.
Setting those to the ones as described in the documentation:
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CONFIG_USB_GADGET_VENDOR_NUM=0x1b67 CONFIG_USB_GADGET_PRODUCT_NUM=0x4fff |
Gives us following results:
lsusboutput gives following output:Bus 003 Device 010: ID 1b67:5ffe
Note that in this case the PID is also different than specified in the configuration.
I have also used the recent master branch and above information applies there as well.
In this case, we are able to flash u-boot.img via SDP.
On more thing to do before flashing u-boot.img is to add VID / PID pair
to imx_usb config:
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echo '0x1b67:0x5ffe, mx6_usb_sdp_spl.conf' >> imx_usb.conf |
Now we can download SPL and u-boot.img with command below:
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./imx_usb SPL && sleep 1 && ./imx_usb u-boot.img |
output of u-boot.img booting:
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U-Boot SPL 2018.01-00272-g0434429f989d (Jan 18 2018 - 12:56:59) Trying to boot from USB SDP SDP: initialize... SDP: handle requests... Downloading file of size 357536 to 0x177fffc0... done Jumping to the header at 0x177fffc0 Header Tag is not an IMX image U-Boot 2018.01-00272-g0434429f989d (Jan 18 2018 - 12:56:59 +0100) CPU: Freescale i.MX6DL rev1.3 996 MHz (running at 792 MHz) CPU: Commercial temperature grade (0C to 95C) at 60C Reset cause: POR Board: MX6 Hummingboard2 DRAM: 1 GiB MMC: FSL_SDHC: 0 Card did not respond to voltage select! mmc_init: -95, time 58 *** Warning - MMC init failed, using default environment No panel detected: default to HDMI Display: HDMI (1024x768) In: serial Out: serial Err: serial Net: FEC Hit any key to stop autoboot: 0 Card did not respond to voltage select! mmc_init: -95, time 58 ** Bad device mmc 0 ** Card did not respond to voltage select! mmc_init: -95, time 57 Device 0: Model: Firm: Ser#: Type: Hard Disk Capacity: not available ... is now current device ** Bad device size - sata 0 ** starting USB... USB0: Port not available. USB1: USB EHCI 1.00 scanning bus 1 for devices... 2 USB Device(s) found scanning usb for storage devices... 0 Storage Device(s) found Device 0: device type unknown ... is now current device ** Bad device usb 0 ** ** Bad device usb 0 ** FEC Waiting for PHY auto negotiation to complete. |
The interesting thing is that whenever we enter U-Boot prompt and enter SDP
mode:
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=> sdp sdp - Serial Downloader Protocol Usage: sdp <USB_controller> - serial downloader protocol via <USB_controller> => sdp 0 SDP: initialize... SDP: handle requests... |
The USB PID seen by my host PC changes to the one set in the configuration:
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Bus 003 Device 025: ID 1b67:4fff |
Load SPL and u-boot.img in one run
It is possible to download both SPL and u-boot.img with one imx_usb
command execution. To do that, we need to create configuration files with
following content:
imx_usb.conf:
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cat << EOF > imx_usb.conf #vid:pid, config_file 0x15a2:0x0061, mx6_usb_rom.conf, 0x1b67:0x5ffe, mx6_usb_sdp_spl.conf EOF |
mx6_usb_rom.conf
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cat << EOF > mx6_usb_rom.conf mx6_qsb hid,1024,0x910000,0x10000000,1G,0x00900000,0x40000 SPL:jump header2 EOF |
mx6_usb_sdp_spl.conf:
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cat << EOF > mx6_usb_sdp_spl.conf mx6_spl_sdp hid,uboot_header,1024,0x10000000,1G,0x00907000,0x31000 u-boot.img:jump header2 EOF |
Above configuration files are also present in 3mdeb fork of imx_usb_loader
With such configuration in place, calling ./imx_usb gives following output:
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config file <.//imx_usb.conf> vid=0x15a2 pid=0x0061 file_name=mx6_usb_rom.conf -> vid=0x1b67 pid=0x5ffe file_name=mx6_usb_sdp_spl.conf config file <.//mx6_usb_rom.conf> parse .//mx6_usb_rom.conf Trying to open device vid=0x15a2 pid=0x0061 Interface 0 claimed HAB security state: development mode (0x56787856) == work item filename SPL load_size 0 bytes load_addr 0x13f00000 dcd 0 clear_dcd 0 plug 0 jump_mode 3 jump_addr 0x00000000 == end work item loading binary file(SPL) to 00907400, skip=0, fsize=dc00 type=aa <<<56320, 56320 bytes>>> succeeded (status 0x88888888) jumping to 0x00907400 config file <.//mx6_usb_sdp_spl.conf> parse .//mx6_usb_sdp_spl.conf Trying to open device vid=0x1b67 pid=0x5ffe. Interface 0 claimed HAB security state: development mode (0x56787856) == work item filename u-boot.img load_size 0 bytes load_addr 0x03f00001 dcd 0 clear_dcd 0 plug 0 jump_mode 3 jump_addr 0x00000000 == end work item loading binary file(u-boot.img) to 177fffc0, skip=0, fsize=574a0 type=aa <<<357536, 358400 bytes>>> succeeded (status 0x88888888) jumping to 0x177fffc0 |
and the board boots with U-Boot as shown previously.
Summary
imx_usb_loaderis really handy tool for downloading binaries (especially the bootloader) directly into memory.- I’ve run into some strange behavior of
U-BootUSB Gadget devicePID. I will try to track down what really happens in the code there. - I’ve run into some outdated
U-Bootdocumentation. I can try updating it. - Configuration files for
imx_usb_loadercan be found at 3mdeb fork - Final configuration of
U-Boottarget for Hummingboard Edge which addsSDPsupport can be found on 3mdeb fork - I am going to present next steps towards our goal in an upcoming post from this series.
