Help booting iMX6ULL

[pedropr]

Hi everyone! Hope you're doing well.

I have a custom board which includes iMX6ULL processor and I'm trying to bring life to it but I'm not being able. I also have Colibri-iMX6ULL with Aster Carrier Board to test the same thing.

The main goal here is to run OS from SD card. But configuring BOOT_MODE[0]=0 and BOOT_MODE[1]=1 (with jumpers) and setting BOOT_CFG1, BOOT_CFG2 and BOOT_CFG4 with pulldowns and pullups doesn't do a thing (using pins LCD_DATA0 to LCD_DATA23).

Board aparently is dead with this steps. As the OS, I'm building it with Yocto. Recipes: core-image-minimal and tdx-reference-minimal-image. Both tested in Colibri-iMX6ULL and working good.

Next I tried to load and boot the bootloader generated with those recipes 'u-boot-nand.imx' using UUU with SDP protocol.

What I did is the following:
1) Connect custom board through USB-OTG to PC (using Ubuntu mounted in virtual machine).

2) PC recognized the device and show it as in Recovery Mode (good).

3) Connect UART_1 to PC and run minicom to see outputs to the console.

4) Run in UUU: sudo ./uuu SDP: boot -f u-boot-nand.imx.

5) Execution shows no errrors.

6) Now I the device as Toradex USB download gadget (good, i think).

This process works good with Colibri-iMX6ULL. I see a new U-Boot booting in the console output after this steps.

But with custom board I'm not seeing anything in the console. I saw the UART1_TX output with a oscilloscope and not seeing activity either.

Is there anything that I'm missing? Should I download a kernel image before loading the bootlodaer? Where could I see the memory addr to do this?

I'm new to embedded linux development and struggling a bit whith this.

Thank yoy very much!

Best regards.

[AldoG]

Hello,

If you're able to get into Linux then I would say that it was correctly flashed, I cannot comment much on the HW settings nor the recipe you have used since it is from Toradex, I would recommend to contact them for support on this.

Regarding your custom board please make sure that you have run the DDR test and you have built for your specific target.

https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/i-MX-6-7-DDR-Stress-Test-Tool/ta-p/11082...

Best regards,
Aldo.

[pedropr]

Hi Aldo.
Thanks for your repply.
I will not ask any question about Toradex board here, I'm just using it as reference for the custom board.
But I do have a few other questions if you don't mind for the custom board:
1) The steps I made are correct? Should I need to download to the custom board iMX6ULL processor the uImage (kernel) besides u-boot-nand.imx (bootloader) file?
2) The custom board has 512MB external SDRAM - DDR3L. Does u-boot use it? Or it runs with internal OCRAM?
3) In case u-boot doesn't use it. Why would I need to run the DDR test at this point? Considering SDP download went succesfully, but not seing anything in the console after that.

Best regards,
Pedro.

[AldoG]

Hi,

1) Yes, your steps looks correct, if you're expecting to get further than just uboot then yes, you would need to flash both kernel image (uImage) and the file system. Also, please note that uboot-nand.imx seems to be a uboot specified for NAND flash by its name convention so I would say you should use the one for SD card, since you’re targeting for this one.

2) Uboot runs in OCRAM, once it does finish execution it is moved to DDR.

3) Uboot, and ROM code, initialize all necessary peripherals for execution this includes the DDR phy which if fails it does not boot correctly, even if it does this could bring problems later on.

Best regards,
Aldo.

[pedropr]

Hi Aldo,
thanks for the quick repply.
I made the DDR test that you suggested. I ran the calibration and stress test at 400MHz, no error shown. Files attached of config and results.
I tested another frequencies too, it shown some errors at 158MHz, 163MHz for example (written data differs from read data). Is this saying something?

I'm still not being able to see anything in the console through UART1 and UART2. I attached the schematics for this parts. I connect UART1 to the PC through a RS232 interface.
There are some others outputs shown in the schematics but are all disconnected.
Is there something in particular that I should check for the console output?
Let me know if I can provide more information.

Much appreciated!
Best regards,
Pedro.

[AldoG · Accepted solution]

Hi,

Did you update the flash_header.S file with the values of a passing DDR Stress test?

Also, which UART did you configure to be the console output?
This is usually set in the uboot configuration file, i.e. for our board:
https://github.com/nxp-imx/uboot-imx/blob/lf_v2022.04/include/configs/mx6ullevk.h#L31

#define CONFIG_MXC_UART_BASEUART1_BASE

Best regards,
Aldo.

[pedropr]

Hi Aldo.

I finally got an output to the console building u-boot from source code and using mx6ull_14x14_evk_defconfig. Apparently, the u-boot used for Colibri-iMX6ULL don't work on my imx6ull custom board.

Now with U-Boot running I have more options to boot from the SD card.

Just out of curiousity (I'll work on this later). Is it possible to change the default uart output console from UART1 to UART8? Setting:

#define CONFIG_MXC_UART_BASE UART8_BASE

in /include/configs/mx6ullevk.h didn't work.

Thank very much for your help. I was struggling with this for a few weeks.

Best regards,

Pedro.