i.mx6ULL separate boot and kernel media?

[dluberger]

I'm having a hard time sourcing in low volume a flash device that can hold both the boot loader (u-boot) and the yocto project linux build (i.e., the kernel). Together, these need about 900MB of storage so I need at least 8Gb (1GB) of flash memory. Most of that I'm sure is the kernel, so what I'm wondering is: can I have the bootloader run on something small but cheap and reliable like spi NOR flash and then have the kernel run on an external SD card? My issue is that I just don't want to rely on an external SD card for my product to work. With the bootloader and console port, I can do all my diagnostic stuff without even having linux running, and at least if they lose the SD card, I can still debug the device or (I think) even do SFTP (to download via wifi?) a new kernel.  Does this make sense?  I hate that eMMC isn't readily available. Sure, Mouser and Digikey carry a few, but the one benefit of using an SD card is I can stick essentially any SD card in there.  With something like spi NOR flash, I have ready availability from lots of manufacturers with a common pinout, and it's fairly fast and generally is only a couple bucks.  NAND flash just seems like a huge pain to connect and configure (so many pins!) and having read about things like error correction and bad block management, it's a wonder to me that anyone uses it outside of SD cards, as it just sounds super unreliable, plus it's expensive and not readily available.

[Carlos_Musich]

Hi David,

rather than the kernel, the root file system is what needs more space in memory. And yes, you can definitely have uboot in NOR flash and kernel with root file system in SD card.

You need to set the fuses to boot from QSPI and configure uboot to look for zImage and device tree in SD card.

Yoy can look at Table 5-1. Boot Device Select and Table 5-2. QSPI Boot Fusemap IMX6ULLRM.pdf

Regards,
Carlos
NXP Technical Support
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[dluberger]

When you say "configure u-boot" to look in the SD card, is that something that's setup prior to compiling u-boot? the only experience i have with u-boot is playing with the command line in the console after it's already loaded on the device; that wouldn't be practical if i have to flash and configure hundreds of devices.

also, do you personally have any experience and/or recommendations for the embedded boot device to use? parallel nand flash just seems scary to me because of the fact that it inherently goes bad over time, but i haven't seen anything anywhere that compares all the different embeddable media types that the i.mx6ull supports in terms of speed and capacity so i'm really shooting in the dark here.