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i.MX7D: boot into secondary boot image of uboot

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i.MX7D: boot into secondary boot image of uboot

‎10-02-2017 02:30 AM
1,625 Views
vishalthanki
Contributor II

Hello Everyone,

I am working on i.MX7D based custom platform with secure boot enabled. We use u-boot as bootloader which is flashed on NAND. I see that u-boot is also stored in a secondary NAND area (secondary bootstream) when flashed using "kobs-ng" utility. Based on this, I have following questions:

  1. Can I force to u-boot to boot from secondary boot-stream (either boot-stream 0 or 1)?
    • In Technical Reference Manual document, I see that PERSIST_SECONDARY_BOOT (SRC_GPR10[30]) can be used to select from which bootstream to use. However, value of PERSIST_SECONDARY_BOOT bit is preserved only across SW reset.
  2. I change the value to PERSIST_SECONDARY_BOOT bit (from 0 to 1, to force booting from boot-stream 1) from u-boot prompt using following command, is it correct?
    • # mw.l 0x30390098 0x40000000
    • I noticed that after running this command, if I run "reset" command on u-boot, it still boots from boot-stream 0. Can you please point out what am I doing wrong?
  3. According to TRM section 6.6.5.2.2:

    • If during primary image read there is a page with a number of errors higher than ECC can
      correct, the boot ROM will turn on PERSIST_SECONDARY_BOOT bit and perform
      SW reset (After SW reset, secondary image is used).

  • I try to force the above situation by writing garbage data to 1st page of boot-stream 0 (i.e. at offset 0x00200000). Now I expect the Boot ROM to set the PERSIST_SECONDARY_BOOT and perform SW reset, but that does not happen and the device just does not boot. I have to use serial downloader to make the device bootable again.

Thanks,

Vishal

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‎10-03-2017 12:47 AM
1,233 Views
Yuri
NXP Employee
NXP Employee

Hello,

  generally the secondary boot option is intended to be controlled by boot ROM

automatically without special customer's activity (to perform the secondary boot

directly). Note, usually applications cannot cause ECC error in software.  ECC

relates to hardware errors.

Have a great day,
Yuri

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