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Why isn't the eMMC fast-boot failing over to normal boot?

Question asked by Hugh Boddington on Nov 8, 2016
Latest reply on Nov 16, 2016 by igorpadykov

We're using an eMMC 4.4.1 chip with our imx.6 design and trying to boot into u-boot using fast-boot mode (BOOT_CFG1[4]=1).  This mode works if the eMMC is in a pre-idle state (i.e., just after power-on reset).  If the imx.6 is reset without cycling power, the eMMC is NOT in pre-idle and therefore cannot enter fast-boot mode.  That's all fine and good, but the imx.6 FRM suggests that if fast-boot mode fails then the eMMC "boots as a normal MMC card from the selected boot partition" (that's a quote from table 8-16 of the FRM).  This isn't happening.  Instead, the imx.6 locks up and won't boot at all.  It's crucial for us that this fail-over behaviour works properly:


Desired behaviour:

Attempt fast-boot -> Fail -> Attempt normal-boot -> Succeed


Observed behaviour:

Attempt fast-boot -> Fail -> Lock up


Am I doing something wrong?  If I manually disable fast-boot mode then the boot process works properly, but I'm not seeing that fast-boot fail-over behaviour.  We do not have a reset pin connected so it's not feasible to enable the hardware eMMC reset (BOOT_CFG1[1]). 


Any thoughts?


Additional information: Our BOOT_CFG is set to 0x0000DC70