U-Boot Environmental Variables

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U-Boot Environmental Variables

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ShaneKaiser
Contributor II

Hello Everyone,

I have a question regarding a U-Boot environment variable:

loadaddr=70800000

mmc read ${loadaddr} 0x800 0x1800; bootm

What exactly is the mmc command doing here? How does one come up with loadaddr=70800000?

From what I understand U-Boot will read data from the sd card at 2048*512=1MB (starting location of uImage on the sd card) and keep reading for 6144*512=3MB (the size of the kernel) and take this data and copy it to address 0x70800000 in memory? So U-Boot is installing the kernel at the memory address 0x70800000?

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Yuri
NXP TechSupport
NXP TechSupport

I am not sure if kernel decompressor  is position independent, it may be build to use absolute addresses (0x70800000).  

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ShaneKaiser
Contributor II

Thanks for the response Yuri.

Why the memory address 0x70800000? I have noticed some people use other memory addresses. What is the thinking here?

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Yuri
NXP TechSupport
NXP TechSupport

You are right.


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