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 U-Boot SD Only 
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Joined: Mon Jan 27, 2014 5:07 pm
Posts: 29
Location: US
Post U-Boot SD Only
I have some questions about the U-Boot setup on the Utilites. We’re trying to make sure we can run U-Boot from the SD card without using the onboard U-Boot, and it seems we can achieve this on the Utilites. We have some questions on this process:

1. How does the device know there is a valid U-Boot image on the SD card before invoking the U-Boot in SPI flash?
2. Can a standard imx.6 of similar implementation as the Utilite Standard be capable of doing this or did CompuLab add/change something?


Fri Jul 18, 2014 10:17 pm
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Joined: Sun Nov 24, 2013 9:13 am
Posts: 210
Post Re: U-Boot SD Only
bkraus wrote:
I have some questions about the U-Boot setup on the Utilites. We’re trying to make sure we can run U-Boot from the SD card without using the onboard U-Boot, and it seems we can achieve this on the Utilites.


You can achieve this. You must create a bootable SD card for that (follow instructions for CM-FX6): http://compulab.co.il/workspace/mediawi ... le_SD_card

bkraus wrote:
1. How does the device know there is a valid U-Boot image on the SD card before invoking the U-Boot in SPI flash?

The i.MX6 bootROM is looking for an IVT and DCD in the first 4Kbytes of the program image, if these structures are not found, SD boot is considered as failed. Upon a failed boot, the bootROM uses a feature called "recovery devices", which then tries booting from the SPI Flash.

You can get more information on that process from the i.MX6 TRM.


Sun Jul 20, 2014 11:09 am
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Joined: Mon Jan 27, 2014 5:07 pm
Posts: 29
Location: US
Post Re: U-Boot SD Only
How did you configure the I.MX6 to achieve this? From my understanding you'd have to set the BOOT_CFG1-4 arrays to something like 0x58000070, which sets it to MMC boot with recovery devices on (spi). Running "imxotp read 5" on the Utilite it shows the value as 0x0. This confuses me. Are you using GPIO to configure the bootROM?


Tue Jul 22, 2014 9:52 pm
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Joined: Sun Nov 24, 2013 9:13 am
Posts: 210
Post Re: U-Boot SD Only
We do not burn fuses in production, CM-FX6 uses GPIO overrides to set boot sequence.


Wed Jul 23, 2014 6:41 am
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Joined: Mon Jan 27, 2014 5:07 pm
Posts: 29
Location: US
Post Re: U-Boot SD Only
Thanks for the answers Alex. Hopefully these aren't too difficult:

1) Is the Utilite configured for MMC or SD boot?

2) Do you know the location in memory I can read BOOT_CFG[1,2,3,4] as programmed by GPIO? We're trying to copy the configuration into fuses but I can't seem to find where the GPIO configuration for the BOOT_CFG arrays is stored.

I've tracked down the EIM_DA[0-15] pins (which are the GPIO inputs) to the SRC_BOOT_CFG[0-15] Signals. I can't seem to find where those signals can be read.


Wed Jul 23, 2014 4:21 pm
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